**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy** A thesis Submitted by **SULEMAN SHAFQAT (70140070), SYED HASSAN RAZA (70140066), ALI RAZA (70140062), Muhammad Faisal (70139979)** ![](media/image1.png){width="2.515277777777778in" height="1.3645833333333333in"} **CARDIAC PERFUSION TECHNOLOGY** **Supervisor : Miss Rimsha Noor** **M.phil Quality Management** **Department of Emerging Allied Health Technology** **THE UNIVERSITY OF LAHORE** **(2022-2026)** **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging Allied Health Technologies** **UNDERTAKING BY STUDENT** We **Suleman** **Shafaqat, Syed Hassan Raza, Ali Raza, Muhammad Faisal Regd**. No. 70140070, 70140066, 70140062, 70139979 declare that the contents of my research project entitled **"Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy** **"**are based on my own research findings and have not been taken from any other work except the references and has not been published before. **Student Name** **Suleman Shafqat** **Syed Hassan Raza** **Ali Raza** **Muhammad Faisal** **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging Allied Health Technologies** **SUPERVISORY COMMITTEE** We, the Supervisory Committee certify that the contents and the form of thesis submitted by **Suleman Shafaqat, Syed Hassan Raz, Ali Raza, Muhammad Faisal** **(70140070, 70140066, 70140062, 70139979 )** research project entitled "**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy"** have been found satisfactory and recommended for the award of degree of Cardiac Perfusion Technology. **Supervisor : Miss Rimsha Noor** Demonstrator Department of Emerging Allied Health Technologies Faculty of Allied Health Sciences The University of Lahore **HOD: Dr. Nimra Aziz** HOD/Assistant Professor Department of Emerging Allied Health Technologies Faculty of Allied Health Sciences The University Of Lahore **Dean: Prof. Dr. Ashfaq Ahmed** Faculty of Allied Health Sciences The University Of Lahore **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging Allied Health Technologies** **SUPERVISIOR LETTER** We Suleman Shafqat, Syed Hassan Raza, Ali Raza, Muhammad Faisal certify that the contents and the form of research project entitled "**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy** " submitted by **Suleman Shafqat, Syed Hassan Raza, Ali Raza, Muhammad Faisal** Regd. No 70140070, 70140066, 70140062 70139979 have been found satisfactory and recommend it for the evaluation of the External Examiner for the award of degree of **Cardiac Perfusion Technology** **Supervisor name Miss Rimsha Noor** **Qualification** M. Phil Quality management **Designation** Demonstrator **Signature** **Date** **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging ALLIED Health Technologies** **BIOSTATISTICIAN LETTER** We **Suleman Shafqat, Syed Hassan Raza, Ali Raza, Muhammad Faisal** certify that the statistical analysis of research project entitled "**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy**" submitted by **Suleman Shafqat, Syed Hassan Raza, Ali Raza, Muhammad Faisal** Regd. No. [70140070, 70140066, 70140062, 70139979]{.underline} have been found satisfactory for the award of degree of Cardiac Perfusion Technology **Bio-statistician Name :** Miss Areej Imtiaz **Qualification** M. Phil Biostatistics **Designation** Biostatistician (lecturer) **Signature** **Date** **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging Allied Technologies** **EXAMINATION COMMITTEE** The research project entitled "**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy**" and its presentation of [Suleman Shafaqat, Syed Hassan Raza , Ali Raza, Muhammad Faisal]{.underline} (70140070, 70140066, 70140062, 70139980) Was held on at the University Institute of Emerging Allied Health Technologies, Faculty of Allied Health Sciences, The University of Lahore. The Supervisory and Examination Committee gave satisfactory remarks on the Research project and Presentation and approved for the award of the degree of **[Cardiac Perfusion Technology.]{.underline}**. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **External Examiner** **Internal Examiner** Miss Shazia Batool Miss Mehreen Shahbaz Lecturer Lecturer Faculty of Allied Health Sciences Faculty Of Allied Health Science The University of Lahore The University Of Lahore \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Principal/HOD** Dr Nimra Aziz HOD/ Assistant Professor Department Of Emerging Allied Health Technologies The University Of Lahore **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_** **Dean: Prof. Dr. Ashfaq Ahmed** Faculty of Allied Health Sciences The University Of Lahore **The University of Lahore** **Faculty of Allied Health Sciences** **Department of Emerging Allied Health Technologies** **PLAGIARISM EVALUATION REPORT** This is to certify that I have examined the Turnitin report of the thesis entitled "**Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy**".The thesis contains no text that can be regarded as plagiarism.The overall similarity index obtained from the Turnitin software is 14%. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Librarian Supervisor** Muhammad Murtaza Miss Rimsha Noor M.Phil in Library& Information Sciences M.phil Quality Management **Date** 22-05-2026 []{#_Toc230618462 .anchor}**LIST OF ABBREVIATIONS** ----------------------------------------------------------------------- **Abbreviations** **Full form** ----------------------------------- ----------------------------------- AKI Acute kidney injury CSA Cardiac surgery associated CABG Coronary artery bypass grafting CPB Cardiopulmonary bypass ADQI Acute Disease Quality Initiative TCRAT Acute Disease Quality Initiative CAD Coronary artery disease DM Diabetes melitus MICS Minimally invasive cardiac surgery ----------------------------------------------------------------------- # TABLE OF CONTENTS {#table-of-contents .unnumbered} # Contents {#contents .TOC-Heading1 .unnumbered} [LIST OF ABBREVIATIONS [xii](#_Toc230618462)](#_Toc230618462) [TABLE OF CONTENTS [xiii](#table-of-contents)](#table-of-contents) [ABSTRACT [xvii](#abstract)](#abstract) [CHAPTER 1 [1](#chapter-1)](#chapter-1) [INTRODUCTION [1](#introduction)](#introduction) [1.1 RATIONALE OF STUDY [5](#rationale-of-study)](#rationale-of-study) [CHAPTER 2 [6](#chapter-2)](#chapter-2) [LITERATURE REVIEW [6](#literature-review)](#literature-review) [CHAPTER 3 [19](#chapter-3)](#chapter-3) [3.1 OBJECTIVES [19](#objectives)](#objectives) [3.2 HYPOTHESIS [19](#hypothesis)](#hypothesis) [3.3 OPERATIONAL DEFINITIONS [20](#operational-definitions)](#operational-definitions) [CHAPTER 4 [21](#chapter-4)](#chapter-4) [MATERIAL AND METHODS [21](#material-and-methods)](#material-and-methods) [4.1 Study Design [21](#_Toc230618476)](#_Toc230618476) [4.2 Study Settings [21](#_Toc230618477)](#_Toc230618477) [4.3 Duration of Study: [21](#_Toc230618478)](#_Toc230618478) [4.4 Sample Size: [21](#_Toc230618479)](#_Toc230618479) [4.5 Sampling Technique [1](#_Toc230618480)](#_Toc230618480) [4.6 Sampling Selection: [1](#sampling-selection)](#sampling-selection) [**4.6.1** **Inclusion Criteria** [1](#_Toc230618482)](#_Toc230618482) [**4.6.2** **Exclusion Criteria** [1](#_Toc230618483)](#_Toc230618483) [4.7 ETHICAL CONSIDERATIONS [2](#ethical-considerations)](#ethical-considerations) [The rules and regulations set by the ethical committee of university of Lahore will be followed while conducting the research and the rights of the research participants will be respected. [2](#_Toc230618485)](#_Toc230618485) [• Written informed consent (attached) will be taken from all the participants. [2](#_Toc230618486)](#_Toc230618486) [• All information and data collection will be kept confidential. [2](#_Toc230618487)](#_Toc230618487) [• Participants will remain anonymous throughout the study. [2](#_Toc230618488)](#_Toc230618488) [• The subjects will be informed that there are no disadvantages or risks on the procedure of the study. [2](#_Toc230618489)](#_Toc230618489) [• They will also be informed that they will be free to withdraw at any time during the process of the study. [2](#_Toc230618490)](#_Toc230618490) [4.8 DATA COLLECTION PROCEDURE [3](#data-collection-procedure)](#data-collection-procedure) [4.9 DATA ANALYSIS PROCEDURE [4](#data-analysis-procedure)](#data-analysis-procedure) [CHAPTER 5 [5](#chapter-5)](#chapter-5) [RESULTS [5](#results)](#results) [CHAPTER 6 [45](#chapter-6)](#chapter-6) [DISCUSSION [45](#discussion)](#discussion) [CHAPTER 7 [51](#chapter-7)](#chapter-7) [7.1 Conclusions [51](#conclusions)](#conclusions) [7.2 Recommendations [52](#recommendations)](#recommendations) [7.3 Limitations [53](#limitations)](#limitations) [CHAPTER 8 [54](#chapter-8)](#chapter-8) [REFERENCES [54](#references)](#references) [CHAPTER 9 [58](#chapter-9)](#chapter-9) [ANNEXURES [58](#annexures)](#annexures) [9.1 ADD THE TABLES AND FIGURES ACCORDING TO THE DEPARTMENTAL REQUIRMENT [58](#add-the-tables-and-figures-according-to-the-departmental-requirment)](#add-the-tables-and-figures-according-to-the-departmental-requirment) [9.2 CONSENT FORMS [59](#consent-forms)](#consent-forms) [9.3 PROFORMA/QUESTIONNAIRE [61](#proformaquestionnaire)](#proformaquestionnaire) **\ ** **LIST OF TABLES** [**Table 5. 1: Comparison of Baseline Characteristics** [6](#_Toc230618411)](#_Toc230618411) [**Table 5. 2 Comparison of Quantitative Variables Between the Study Groups** [8](#_Toc230618412)](#_Toc230618412) [**Table 5. 3; Frequency of Age distribution range (N=150)** [9](#_Toc230618413)](#_Toc230618413) [**Table 5. 4:FREUQNCY DISTRIBUTION OF GENDER (n=150)** [10](#_Toc230618414)](#_Toc230618414) [**Table 5. 5: Frequency distribution of BMI category (n=150)** [11](#_Toc230618415)](#_Toc230618415) [**Table 5. 6: Frequency distribution of diabetes mellitus (N=150)** [12](#_Toc230618416)](#_Toc230618416) [**Table 5. 7: Frequency distribution of hypertension (n=150)** [13](#_Toc230618417)](#_Toc230618417) [**Table 5. 8 frequency distribution of chronic kidney disease (CKD) (N=150)** [14](#_Toc230618418)](#_Toc230618418) [**Table 5. 9: frequency distribution of smoking status (n=150)** [14](#_Toc230618419)](#_Toc230618419) [**Table 5. 10: Descriptive Statistics of baseline Serum Creatinine Statistics (mg/dL) --- Total Sample and by Surgical Group** [15](#_Toc230618420)](#_Toc230618420) [**Table 5. 11: Descriptive Statistics of basline eGFR (mL/min/1) --- Total Sample and by Surgical Group** [16](#_Toc230618421)](#_Toc230618421) [**Table 5. 12: Descriptive Statistics of LVEF(%) --- Total Sample and by Surgical Group** [18](#_Toc230618422)](#_Toc230618422) [**Table 5. 13: Descriptive Statistics of preop hemoglobin(g\\dl) --- Total Sample and by Surgical Group** [19](#_Toc230618423)](#_Toc230618423) [**Table 5. 14:Descriptive Summary of Postoperative Renal parameters** [21](#_Toc230618424)](#_Toc230618424) [**Table 5. 15: Shapiro-Wilk Normality Test Results for Continuous Variables by Surgical Group** [23](#_Toc230618425)](#_Toc230618425) [**Table 5. 16: Comparison of Serial Postoperative Renal Parameters** [30](#_Toc230618426)](#_Toc230618426) [**Table 5. 17: Comparison of AKI Incidence Between Surgical Groups** [37](#_Toc230618427)](#_Toc230618427) [**Table 5. 18: AKI Stage Distribution by Surgical Group** [39](#_Toc230618428)](#_Toc230618428) [**Table 5. 19: Comparison of Categorical Renal Parameters at 48 Hours** [41](#_Toc230618429)](#_Toc230618429) [**Table 5. 20: Risk Factors Associated with AKI Development --- Odds Ratio Analysis** [43](#_Toc230618430)](#_Toc230618430) **LIST OF FIGURES** [**Figure 5. 1 Age range distribution of the study population(N=150)** [9](#_Toc230618431)](#_Toc230618431) [**Figure 5. 2 Gender distribution in the study population** **(N=150)** [10](#_Toc230618432)](#_Toc230618432) [**Figure 5. 3 BMI category distribution** [11](#_Toc230618433)](#_Toc230618433) [**Figure 5. 4 diabetes mellitus distribution in study population** [12](#_Toc230618434)](#_Toc230618434) [**Figure 5. 5: Hypertension distribution in sample population** [13](#_Toc230618435)](#_Toc230618435) [**Figure 5. 6 chronic kidney disease in sample population.** [14](#_Toc230618436)](#_Toc230618436) [**Figure 5. 7: smokig status distribution** [15](#_Toc230618437)](#_Toc230618437) [**Figure 5. 8 Baseline Serum Creatinine Distribution (N = 150).** [16](#_Toc230618438)](#_Toc230618438) [**Figure 5. 9: *Baseline eGFR Distribution (N = 150).*** [17](#_Toc230618439)](#_Toc230618439) [**Figure 5. 10: Baseline Left Ventricular Ejection Fraction (LVEF) Distribution (N =** [18](#_Toc230618440)](#_Toc230618440) [**Figure 5. 11: Distribution of LVEF Categories Among Study population (N = 150)** [20](#_Toc230618441)](#_Toc230618441) [**Figure 5. 12 *Preoperative Haemoglobin Distribution (N = 150).*** [20](#_Toc230618442)](#_Toc230618442) [**Figure 5. 13 Distribution of Surgical Approach from Sample Population** [21](#_Toc230618443)](#_Toc230618443) [**Figure 5. 14 Serum Creatinine Distribution at 24 Hours Postoperatively (N=150).** [25](#_Toc230618444)](#_Toc230618444) [**Figure 5. 15: Serum Creatinine Distribution at 48 Hours Postoperatively (N=150).** [25](#_Toc230618445)](#_Toc230618445) [**Figure 5. 16: Serum Creatinine Distribution at 72 Hours Postoperatively (N=150).** [26](#_Toc230618446)](#_Toc230618446) [**Figure 5. 17 *Low Urine Output Distribution in Study Population (N=150).*** [26](#_Toc230618447)](#_Toc230618447) [**Figure 5. 18 BUN at 48 Hours Distribution (N=150).** [27](#_Toc230618448)](#_Toc230618448) [**Figure 5. 19: *BUN Category Distribution at 48 Hours (N=150).*** [27](#_Toc230618449)](#_Toc230618449) [**Figure 5. 20 *Serum Urea at 48 Hours Distribution (N=150).*** [28](#_Toc230618450)](#_Toc230618450) [**Figure 5. 21 *Urea Category Distribution at 48 Hours (N=150).*** [28](#_Toc230618451)](#_Toc230618451) [**Figure 5. 22 eGFR at 48 Hours Distribution (N=150).** [29](#_Toc230618452)](#_Toc230618452) [**Figure 5. 23 *eGFR Category Distribution at 48 Hours (N=150).*** [29](#_Toc230618453)](#_Toc230618453) [**Figure 5. 24 Serial serum creatinine trend from baseline through 72 hours postoperatively** [32](#_Toc230618454)](#_Toc230618454) [**Figure 5. 25 eGFR trend from baseline to 48 hours postoperatively by surgical approach**. [33](#_Toc230618455)](#_Toc230618455) [**Figure 5. 26 Serum urea at 48 hours postoperatively by surgical approach.** [34](#_Toc230618456)](#_Toc230618456) [**Figure 5. 27 Distribution of serum creatinine, eGFR, and serum urea at 48 hours by surgical approach.** [35](#_Toc230618457)](#_Toc230618457) [**Figure 5. 28 Distribution of creatinine change and creatinine ratio at 48 hours by surgical approach**. [36](#_Toc230618458)](#_Toc230618458) [**Figure 5. 29: Comparison of Early AKI Incidence Between Surgical Groups (N=150).** [38](#_Toc230618459)](#_Toc230618459) [**Figure 5. 30 *AKI Stage Distribution Between Surgical Groups (N=150).*** [40](#_Toc230618460)](#_Toc230618460) [**Figure 5. 31 Prevalence of risk factors in patients with and without early AKI.** [44](#_Toc230618461)](#_Toc230618461) # ABSTRACT {#abstract .unnumbered} **Background:** Acute kidney injury is one of the most life threatening situation which can develop after cardiac surgeries and directly linked to morbidity, mortality and longer stay of hospitalization. The traditional conventional approach in performing on-pump CABG using a centralsternotomy procedure causes a greater surgical damage as well as a systemic inflammation response, while minithoracotomy can promots better renal outcomes. **Objective(s):**To compare the incidence and severity of early AKI (48--72 hours after on-pump CABG) between minimally invasive anterior minithoracotomy and conventional median sternotomy approaches. **Methodology:**Comparison study for cross section was conducted on 150 patients that went through an on pump CABG surgery at Umar Hospital & Cardiac Center and Gulab Devi Chest Hospital. Both the patient groups had 75 patients each and these groups included Minimally invasive CABG group and conventional median sternotomy CABG group. The preoperative data for patients was documented and the renal parameters that were analyzed postoperatively were the levels of serum creatinine, eGFR, serum urea, BUN, and urine output, all in 48-72 hours after the surgery. Early AKI was established according to KDIGO 2012 guidelines and the statistical analysis included Chi-square, Mann-Whitney U test, and independent samples t-test where p ≤0.05 indicated statistical significance. **Results:** Overall frequency of early onset AKI was 30.7%. Early AKI was noted in 13.3% patients of the Minimally invasive approach and in 48.0% of patients in the Conventional approach group. There was statistically significant difference between groups (p \< .001). AKI stages 2 and 3 were more prevalent in Conventional approach group. Serum creatinine, serum urea and BUN were significantly higher while eGFR was significantly lower in the Conventional group when compared to Minimally Invasive group. There was statistically significant correlation between low urine output and AKI. **Conclusion:**Considering on-pump CABG, anterior minithoracotomy had fewer cases of AKI that were milder too, suggesting some protection for early renal function. **Key words:** Acute kidney injury, CABG, minimally invasive cardiac surgery, median sternotomy, KDIGO, serum creatinine, eGFR, cardiopulmonary bypass. # {#section .unnumbered} # CHAPTER 1 {#chapter-1 .unnumbered} # INTRODUCTION {#introduction .unnumbered} CAD is a matter of great importance from the viewpoint of public health and is considered an important cause of mortality and morbidity around the world. Ischemia happens due to the narrowing or blockage of coronary arteries, resulting in less flow of blood to the heart. The patients with CAD will most probably suffer from angina, myocardial infarction, CHF, arrhythmia, and poor quality of life. This procedure remains the most reliable approach for doing revascularization of coronary arteries in patients with multi-vessel CAD, despite the presence of pharmacological treatment and PCI (Ralapanawa & Sivakanesan, 2021). The conventional cardiopulmonary bypass (CPB) system has been used for CABG, one of the most popular and life-saving heart surgery techniques that have been around since the first cardiac surgeries performed in the 1960s. One of the most common types of heart surgery is CABG that can be done through minimally invasive surgery or median sternotomy. Median sternotomy is a method of surgery that provides excellent exposure to the operative site but is associated with increased hospital stay, pain, blood is exposed to air and non-endothelial surfaces which results in platelet activation, activation of the coagulation cascade, micro emboli, and thromboembolic complications. And the risk of complications like organ dysfunction and infection enhance in traditional CPB. In the last few decades, minimally invasive cardiac surgeries (MICS) has been developed as an answer to these problems (M. M. Ozgur et al., 2024). In recent years, innovations in heart surgery have emphasized the importance of optimizing surgical techniques for the purpose of improving patient safety and minimizing organ damage. As the transition from traditional coronary artery bypass graft (CABG) to robotic and hybrid forms indicates a clear tendency towards minimization of trauma and maintenance of graft patency. On-pump surgical devices have been updated with an increased number of biocompatible materials that can prevent the initiation of the systemic inflammatory reaction that leads to Acute Kidney Injury (AKI) (Thakare et al., 2023). In minimally invasive surgeries of heart grafting, incision given to the heart through left anterior thoracotomy. This method enables the surgeon to graft the coronary arteries while avoiding excessive tissue destruction and ensuring stability of the chest wall. Minimally invasive surgeries are thought to be less inflammatory due to limited surgical trauma compared to the sternotomy procedure, resulting in improved postoperative perfusion of vital organs. This is why minimally invasive surgeries have gained wide acceptance around the world(Verevkin et al., 2025). Even though minimally invasive CABG carries multiple advantages perioperatively, issues of concern include long-term efficacy, technical difficulty, steep learning curve, and effects on the occurrence of complications like acute kidney injury (AKI). All post-surgical complications notwithstanding, AKI ranks among the most dangerous and clinically important because it raises the morbidity rate, mortality rate, utilization of intensive care services, and cost of healthcare services. It has been demonstrated that individuals who experience acute kidney damage (AKI) after cardiothoracic surgery have a higher chance of dying. AKI affects 5% to 30% of patients undergoing cardiothoracic surgery.Severe AKI, as defined by a large increase in serum creatinine (Hobson et al., 2009). Because there are over 2 million cardiac operations done each year globally, acute kidney injury (AKI) is an important complication of cardiac surgery and the second leading cause of AKI in the ICU. Acute kidney injury (CSA-AKI) occurs in about 40% of patients following cardiac surgery, with 3% of those requiring some form of renal replacement therapy (RRT) temporarily. Severe AKI leads to increased duration of stay both in hospital and ICU, increased perioperative mortality rate by three to eight folds, and increased health care costs. 54% and 38% five- and seven-year survival rates have been shown to correlate with CSA-AKI along with the higher possibility of mortality at five and seven years(Yu et al., 2023). AKI is commonly defined by KDIGO recommendations as a decrease in urine production or an increase in serum creatinine of ≥0.3 mg/dL during 48 hours or ≥1.5 times baseline within 7 days (Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group, 2012). According to the whole KDIGO criteria, 57.3% of the 1802 adult patients who were hospitalized to 97 various intensive care units worldwide experienced with acute kidney injury. Additionally, death rates and renal function at the time of hospital release were linked to the severity of AKI. 44.3% of postoperative patients sent to the ICU in the same cohort study experienced AKI, according to a subgroup evaluations. Additionally, a correlation between accidental death occurrences, prolonged ventilatory therapy, and RRT was discovered in 26.9% of children and young people presented to the ICU having acquired AKI based on serum Creatinine and Urine output parameters (Schiefer et al., 2023). One of the most common complications following coronary artery bypass grafting (CABG), acute kidney injury (AKI), which is a major risk factor for both early and late mortality and morbidity, has a prevalence following heart surgery that ranges from 1% to 30%. The development of chronic kidney disease following renal failure and in-hospital mortality is also linked with AKI. Higher morbidity, increased lengths of stay in the ICU, and both higher short-term and long-term mortality rates are correlated with small increments in serum creatinine after surgery (Hobson et al., 2009). Acute kidney failure during CABG is associated with many complications, including a high risk of developing chronic renal problems, extended hospitalization, increased medical expenses, and increased mortality and morbidity (Reents et al., 2014). AKI occurs after cardiac surgery because of various pathophysiologic factors in perioperative period leading to complex hemodynamic and inflammatory injury to the kidneys. Post cardiopulmonary bypass (CPB) surgery, the kidney is more susceptible to tubular and endothelial injury because of systemic inflammation, reduced perfusion of the kidney, and increased ischemia and reperfusion injury (Dimopoulos et al., 2023). Additionally, CPB causes hemolysis and blood vessels dysfunction, both of which are linked to postoperative renal damage(Kant et al., 2023). Nephrotoxic substances, intraoperative hypotension, hypoperfusion, and oxidative stress are some of the other factors which worsen the condition of poor renal perfusion and thereby increase the chances of AKI. The pre-existing conditions of diabetes, renal diseases, and hypertension that affect the autoregulatory capacity of the kidneys increase the chances of AKI as a consequence of heart surgery. It can thus be concluded that circulatory disorders and the inflammatory response of CPB are responsible for the occurrence of AKI as a consequence of heart surgery.(Dimopoulos et al., 2023) AKI associated with heart surgery occurs in a multifactorial manner, which involves renal injury from ischemia-reperfusion injury from cardiopulmonary bypass, oxidative stress, systemic inflammatory response, and renal hypo perfusion. Even small increases in serum creatinine concentrations following surgery have been shown to be independently associated with increased hospital stay, increased medical costs, and increased mortality(O'Neal et al., 2016). The minimally invasive CABG procedure was selected due to its lowest number of incisions, low level of trauma, quick recovery, and favorable cosmetic outcome. Due to its efficacy in patients with severe narrowing of the left anterior descending artery when angioplasty is not an option, minimally invasive direct coronary artery bypass (MIDCAB) surgery has been considered an alternative surgical technique as a substitute to conventional CABG (Kettering, 2008).The decreased likelihood of post-operative atrial fibrillation is additional advantage of minimally invasive heart surgery. Additionally, practitioners have demonstrated that a left thoracic mini thoracotomy is a less invasive cardiovascular procedure than a typical sternotomy for reconnecting the left internal mammary artery to the left anterior descending artery(Dieberg et al., 2016). Yet, very little investigation has been done expressly to assess early renal consequences following minimally invasive CABG, especially when compared to traditional methods. Making surgical decisions and improving patient outcomes depend on knowing whether minimally invasive CABG is linked to a lower incidence of early AKI. Therefore, the purpose of this study is to assess the incidence of early AKI between patients undergoing minimally invasive anterior minithoracotomy and those undergoing standard median sternotomy during the initial 72 hours following on-pump CABG. **\ ** ## RATIONALE OF STUDY After on-pump CABG, postoperative AKI is still a serious consequence. While minimally invasive procedures are becoming more common, there is no local data on how they affect early renal outcomes in comparison to traditional sternotomy. In order to promote evidence-based surgical decision-making, the aim of this study is to figure out the frequency of early AKI within 48 to 72 hours in both techniques. **\ ** # CHAPTER 2 {#chapter-2 .unnumbered} # LITERATURE REVIEW {#literature-review .unnumbered} A crucial factor in improving recovery after surgery and lowering perioperative complications is comparing minimally invasive heart surgery with the conventional median sternotomyapproach.Modern cardiovascular surgeons pay a lot of attention to studying the role of various techniques in maintaining organ function especially avoiding the development of a new problem such as cardiac surgery-associated acute kidney injury (CSA-AKI). Since postoperative kidney dysfunction increases the risks of morbidity, mortality, ICU stay time, and financial expenses, the choice of such surgical techniques that minimize these risks plays a crucial role. In order to estimate the safety and efficiency of revascularization techniques, there is needed a comprehensive analysis of multiple parameters related to surgical manipulation, inflammatory reaction, changes in the cardiopulmonary hemodynamics, oxidative stress, and early diagnosis of postoperative complications. The recent literature demonstrates an increased tendency to consider various benefits of CABG with minimal invasiveness, namely less tissue injury, lesser inflammatory activation, easier postoperative recovery, and preservation of kidney function in patients who underwent cardiac surgery(Dost et al., 2025; Sljivo et al., 2025). Acute kidney failure (AKI) is a frequent severe side effect following coronary artery bypass grafting (CABG). According to the criteria applied and the features of the study sample, the reported incidence of postoperatively AKI in patients receiving isolated CABG varies from roughly 4% to over 30%. According to a prospective research by Zeyneloglu and colleagues, the probability of AKI following CABG was approximately 4%. The occurrence of AKI was substantially correlated with longer surgical and cardiopulmonary bypass (CPB) periods, and postoperative AKI in this cohort was also significantly associated with higher death rates(Zeyneloglu et al., 2011). In a multicenter cohort study performed by Rosner et al., it was found out that the development of cardiac surgery-related acute kidney injury continues to be the most common complication in postoperative patients despite the improvements made in perioperative care. It was determined that the long duration of cardiopulmonary bypass, intraoperative hypotension, hemodilution, and activation of inflammation played a role in postoperative renal impairment. Moreover, mild postoperative increases in serum creatinine levels were shown to be independently related to increased risk of mortality and hospital stay(Rosner& Okusa, 2005). In addition, consensus guidelines for CSA-AKI have been formulated through Acute Disease Quality Initiative (ADQI). From the research conducted by Nadim et al., it has been determined that CSA-AKI is a multifactorial disorder, which consists of ischemia reperfusion injury, oxidative stress, systemic inflammation, endothelial dysfunction, and neurohormonal activation. This happens when cardiopulmonary bypass is conducted. The use of perioperative management strategies including reduction of surgical trauma, inflammation, and renal perfusion can improve post-operative kidney function(Nadim et al., 2018) Preoperative and postoperative creatinine levels were assessed in a study conducted by Brown et al., on 1391 patients undergoing CABG in northern New England in 2001. Dialysis patients prior to surgery were not included. To evaluate 90-day survival, data were connected to the National Death Index. The log-rank and Kaplan-Meier methods were applied. Using the percentage rise in creatinine from baseline, patients were categorized as follows: \<25%, 25% to 49%, 50% to 99%, \>, or = 100%. After controlling for age and sex, we evaluated 90-day survival and computed adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) for creatinine groups.In comparison to patients with a smaller rise (\<50%; P\<0.001), those with the biggest creatinine increases (50% to 99% or \> or =100%) had a significantly greater 90-day mortality. The 25% to 49% group did not differ from the referent in terms of adjusted HR and 95% CI. Hence,following CABG surgery, patients with significant creatinine increases (\> or = 50%) have a greater 90-day death rate than those with minor increases(Brown et al., 2006). The causes of AKI after heart surgery are many. They include hemodynamic instability, inflammation, ischemia and reperfusion injury, oxidative stress, microembolization, and nephrotoxicity. All of these factors are inter-related and cause AKI by decreasing renal perfusion, causing vasoconstriction, and damaging tubules and endothelial cells of the kidneys. Cardiopulmonary bypass is significant due to its effects on reducing oxygen delivery to the kidneys, formation of microemboli, alteration in renal perfusion, and systemic inflammation caused by contact of blood with artificial surfaces. Additionally, perioperative nephrotoxic drugs and hemolysis-related free hemoglobin release may worsen renal injury. These mechanisms work together to cause postoperative AKI (Vives et al., 2019). The evaluation of risk factors of CSA-AKI has been the core problem of modern scientific researches in field of cardio surgery. Such cohort study was performed by Wang et al. where authors evaluated the clinical features and frequency of development of AKI following CABG operation. For this purpose, they applied the KDIGO criteria for determination of slight rise in serum creatinine within the first days after surgery. According to the statistics of the study, there were found some statistically significant differences between two groups of patients. These results prove that the patients having the classical median sternotomy procedure and long CPB procedure had significantly high rates of developing AKI in the early postoperative period. As a cause of the described condition, the authors pointed out the extensive tissue injury, activation of complement system and profuse bleeding in the operative period followed by several blood transfusions as a pathogenetic factor leading to the injury of tubular nephron. Hence, the mentioned study proves that the classical technique has a negative impact on kidneys(Wang & Bellomo, 2017). Retrospective comparative study by Puskas et al. compared minimally invasive coronary artery bypass surgery to traditional sternotomy CABG surgery. The researchers found that patients undergoing minimally invasive procedures had less postoperative bleeding, spent fewer days in ICU, had lesser transfusions, and were able to ambulate sooner than those who underwent the traditional procedure. It was noted that the lessened systemic inflammatory response seen in minimally invasive procedures could be the cause(Puskas et al., 2004). The Bernardi et al. (2021) researchers conducted a prospective observational study that aimed at establishing the role of urine neprilysin in the diagnosis of early-stage AKI in patients undergoing cardiac surgeries. It should be mentioned that an interesting point was made about the standard post-surgical monitoring of the renal function, where one of the major problems is that there could be an erroneous estimation of the serum creatinine level of the patient since of dilution of blood due to the CPB circuit priming. To address this issue, urinary neprilysin concentrations were assessed during several perioperative periods. As a result, a significant increase in neprilysin concentration was found in the urine of those patients who developed AKI after the surgery. The authors of the study came to the conclusion that urinary neprilysin could be considered a useful biomarker for the early detection of AKI associated with cardiac surgery procedures. As concerns the current comparative study, this article proves to be relevant in terms of providing important information about the methodological issues, such as limitations associated with the use of serum creatinine in the evaluation of on-pump CABG patients(Bernardi et al., 2021). In order to create an elaborate academic framework on the subject of surgical trauma and renal preservation, it is paramount to consider modern scientific trials on cardiac surgery associated acute kidney injury (CSA-AKI). There exists a vast cohort study by Vandewiele et al., which examined the prevalence and periopeorative triggers for early postoperative acute kidney injury in patients undergoing CABG surgery. Specifically, the investigators compared traditional full median sternotomy approach with the innovative MICS-CABG protocol. The statistics compiled from the above mentioned cohort study demonstrated a remarkably statistically significant difference p\<0.05 between both groups, which showed the prevalence rate of early acute kidney injuries to be much higher among the first one. According to the findings obtained from this research the traditional open-heart approach is responsible for considerable exposure of the patient's bone marrow, skeletal damage, and significant blood loss during surgery, which requires allogeneic transfusion of red blood cells. All these factors induce a pronounced inflammation response and hypoperfusion of the kidneys. Hence, the conclusion drawn by the abovementioned research suggests that the conventional protocol of full sternotomy increases the risk of early postoperative renal impairment(Vandewiele et al., 2020). 1260 consecutive individuals from a multiethnic Southeast Asian community who had a primary isolated coronary artery bypass graft (CABG) procedure were the subject of a retrospective research.From the 36.2% overall frequency, 5.5% required renal replacement treatment. The independent risk factors for AKI identified by multivariate analysis were age, insulin-dependent type 2 diabetes , early levels of serum creatinine (SCr), past myocardial injury (MI), cardiopulmonary bypass (CPB) time, and intra-aortic balloon pump (IABP) utilization.TheSCr and the nsulin-dependent diabetic mellitus (IDDM) continued to be independent markers for patients who needed RRT. Patients who experienced AKI after CABG had a considerably higher early 30-day mortality (11.5% vs. 0.9%). In the same manner, AKI was linked to a minor but statistically significant rise in hospital and intensive care unit (ICU) stays(Hiew et al., 2016). An observational study was conducted by Ozgur et al. (2024) where patients undergoing elective isolated coronary artery bypass grafting via median sternotomy were investigated comparing the MiECC system against the conventional cardiopulmonary bypass operation. In total, 163 patients participated in this study where 83 belonged to the group of closed circuit MiECC while 80 made up the group of open circuit CPB for organ safety evaluation and resource utilization. Statistical analysis performed by the investigators confirmed that the minimized circulatory design of MiECC was responsible for the reduction of preoperative decrease in hematocrit levels and intraoperative blood loss.The number of FFPE and PRBC units transfused was also low (0.1 ± 0.3 units vs. 0.4 ± 0.8 units; p = 0.001 and 1.0 ± 1.3 units vs. 1.6 ± 1.9 units; p = 0.004 respectively). Besides, less time was spent in ICU by the MiECC group (1.2 ± 0.5 days vs. 1.5 ± 1.1 days; p = 0).With regard to kidney preservation, post-operative acute kidney injury occurred less frequently in patients treated using the optimized MiECC technique than in patients operated on using the standard open circuit loop technique (8.3% compared with 14.5%; OR = 1.69). The investigation showed that the closed system enabled surgeries at significantly lower targets of the maximal activated clotting time (ACT) (316 ± 54 s compared with 580 ± 127 s; p = 0.001) without causing any instances of thromboembolic or device line related adverse events. With regard to your thesis, this research will be very helpful because it provides critical information regarding the use of an innovative design that can protect hematocrit stability by avoiding blood-air interaction and prime volume reduction(M. Ozgur et al., 2024). The effect of particular postoperative components, like the cardiopulmonary bypass procedure itself, on renal function has been the subject of certain studies. Although postoperative glomerular filtration capacities decreased following CABG, a combination study revealed that neither the length nor the usage of CPB had any independent relationship to the occurrence of AKI. Yet, AKI\'s significance as a clinical criterion in CABG populations was further supported by the strong impact it had on both premature death and longer-term results(Schopka et al., 2014). A retrospective cohort study involving 2,973 adult subjects without baseline chronic kidney disease requiring intensive care after major cardiothoracic surgery was undertaken by Hobson et al. (2009). This study involved the use of RIFLE criteria for assessing the effect of AKI that was considered even if there were minimal early elevation in serum creatinine levels, on survival outcomes over a period of up to 10 years.Their risk-adjusted Cox proportional hazards model found a statistically significant dose response correlation between AKI severity and survival. The odds ratio was 1.23 for long term mortality for patients categorized in the RIFLE-Risk group, and 2.14 in those with the RIFLE-Failure classification.Significantly, it was noted that patients showing signs of renal function recovery prior to being discharged from the hospital maintained increased risk for long-term mortality compared to patients without perioperative AKI (hazard ratio 1.28).This suggests that acute perioperative renal impairment may cause adverse effects on other systems as well. The results of this study suggest the importance of preventing AKI in cardiac thoracic surgical procedures(Hobson et al., 2009) This study was performed by Shaheen et al., (2020).The purpose of the present study is to identify the incidence and risk factors associated with cardiac surgery-associated acute kidney injury (CSA-AKI). In this connection, a total of 430 adults, who had undergone cardiac surgery with CABG operation at AFIC/NIHD, Rawalpindi, were studied regarding their incidence of CSA-AKI as per AKIN criteria. Referring to the demographic information provided concerning the sample participants of the current study, it can be mentioned that most sample participants of the current study were male aged 55± 11.6 years on average. The independent risk factors for CSA-AKI included prolonged cardiopulmonary bypass time, prolonged aortic cross-clamp time, IABP, inotropic therapy, and red cell concentrates and fresh frozen plasma usage. On the basis of the results of the current study, one may conclude that the key factors of CSA-AKI include hemodynamic instability, excessive utilization of extracorporeal circuitry, and transfusion induced inflammation.The above study serves as an important source for regional literature regarding the connection between perioperative surgical stress and post-operative kidney dysfunction in patients with heart disease in Pakistan. The results obtained from the study add more validity in pursuing the minimally invasive approach for CABG, where minimizing trauma during surgery, reducing the time on bypass, and lowering the need for blood transfusions may contribute to better post-op renal function(Shaheen et al., 2021). In their report, Prowle et al. (2021), as a joint consensus by ADQI and POQI, presented a relevant perioperative model for the study of postoperative AKI (PO-AKI) in adult surgical patients. According to KDIGO guidelines, PO-AKI was described in terms of occurrence of AKI within 7 days after surgery. Moreover, PO-AKD (Postoperative Acute Kidney Disease) was introduced in cases where renal dysfunction was prolonged after this period of time. Considering cardiac surgery, particularly minimally invasive surgery compared with conventional techniques, the above consensus appears to be very important, since it defines PO-AKI as one of the common complications that is linked with higher morbidity and poor patient outcomes in a short- and long-term perspective, such as CKD development, cardiovascular events, and even death. The consensus also describes some main risk factors for PO-AKI such as older age, DM, HTN, preexisting renal dysfunction, heart failure, emergency surgery, and exposure to nephrotoxins that are commonly present in patients undergoing CABG.More importantly, the report highlighted that any instances of PO-AKI, even transient or minor ones, cannot be considered harmless and might affect the kidney in the long run. The report also suggested measures for preventing PO-AKI in surgery, which include early patient risk classification, mean arterial blood pressure maintenance, goal-directed fluid management, avoidance of nephrotoxic agents, and balanced crystalloid use. Hence, this consensus serves as an excellent starting point in both theory and practice concerning the occurrence and prevention of AKI in cardiopulmonary procedures(Prowle et al., 2021). In their paper, Kiani et al. (2012) performed a prospective observational study that examined the specifics of renal impairment while conducting multi-vessel coronary artery bypass grafting through a mini-thoracotomy (MVST). Specifically, the authors compared the results of off-pump thoracotomy procedure (OP-MVST, n=46) with those of the cardiopulmonary bypass supported by peripheral cannulation technique (MVST-PA, n=45). The results of their analysis have shown that even though both procedures had similar baseline risk profile and 30-day composite morbidity/mortality rates, there was a statistically significant difference in the incidence rate of renal failure between the two groups (OP-MVST vs. MVST-PA, 10.87% vs. 0%, p=0.05). On the other hand, the latter procedure involved much more interference with the coagulative system of the patient, causing platelet inhibition and thus leading to increased necessity of blood transfusion. As for your thesis, Kiani et al.\'s paper is one of the critical studies in this area, as it proves that even though using the mini-thoracotomy technique does not require cardiopulmonary bypass, thus reducing systemic stress, the need to manipulate the hemodynamics to perform the grafts without a pump may cause greater ischemic stress in the kidneys, increasing AKI risk(Kiani et al., 2012). Although there is ample evidence of AKI following CABG, little is known regarding the effects of various surgical techniques on renal outcomes. Various retrospective cohort studies have indicated that minimal access coronary artery bypass graft is an excellent clinical alternative for patients as compared to the traditional approach of median sternotomy. For example, various studies that compare the two procedures have found that as compared to CABG, MICS-CABG can lead to lesser bleeding, shorter ventilation duration, and lesser need for blood transfusion without having any significantly different rate of major adverse cardiovascular and cerebrovascular events and death (Sljivo et al., 2025). 25% of patients undergoing heart surgery experience cardiac surgery-associated acute kidney injury (CSA-AKI), especially if they have undergone cardiopulmonary bypass surgery. One of the public health issues with a high prevalence of morbidity and mortality is CSA-AKI. The prognosis of people with renal diseases, including chronic kidney diseases, is poor. The pathogenesis of CSA-AKI is multifactorial, and it is mainly mediated by inflammatory responses and cell injury. Cardiopulmonary bypass, ischemia/reperfusion injury, and activation of the complement and immune systems are among the main factors in the pathogenesis of CSA-AKI(Kamla et al., 2025). In a similar study by Baishya et al. (2017), the perioperative outcomes of Minimally Invasive Cardiac Surgery Coronary Artery Bypass Grafting (MICS-CABG) were compared to the traditional open heart operation using sternotomy technique. The investigators assessed several clinical recovery indicators and observed that while MICS-CABG involved a lengthy operation due to its complicated nature and narrow accessibility, there were also many physiological benefits associated with this procedure. The MICS-CABG patients showed significantly less use of mechanical ventilation, with lesser intraoperative bleeding compared to the controls, hence requiring fewer allogeneic blood transfusions for recuperation. As a result, the minimally invasive surgery patients required less intensive care unit and hospital stay compared to those who went through a complete open heart surgery. This research provides solid evidence that, in spite of the complexity and time-consuming aspect of MICS, the ability of the technique to minimize blood loss and bony injury leads to less systemic stress responsible for AKI and organ dysfunction (Baishya et al., 2017). There are a number of risk factors related to the perioperative period that may cause AKI after heart surgery. The independent risk factors for developing AKI include age, gender (being female), pre-existing cardiac dysfunction before surgery (low ejection fraction, cardiogenic shock, heart failure), emergency surgery, peripheral vascular disease, re-operation, type 1 diabetes mellitus, chronic obstructive pulmonary disease, and perioperative administration of a serine protease inhibitor aprotinin. The risk factor for pre-existing renal dysfunction before surgery, which includes estimated glomerular filtration rate less than 60 ml/min or elevated serum creatinine, is regarded as the highest-risk factor for AKI.. Other risk factors for AKI related to the procedure itself include valvular surgery with or without CABG surgery compared with CABG alone. The other risk factors associated with AKI include the duration of CPB and aortic cross-clamp times, particularly when there are complications and bleeding. Additional risk factors associated with AKI include transfusion of packed red blood cells, hemodilution during CPB, and preoperative anemia, specifically with hemoglobin less than 12.5 mg/dL(Vives et al., 2019) In the case of the comparative study conducted by Saad et al., 2026, it involved a comparison between short-term effects of MICS-CABG and OPCAB performed under ERACS. In the comparative study, the total number of patients under study was 116, which was comprised of pairs. The duration of MICS-CABG operation was longer than that of OPCAB due to its complexity (238.9 ± 65 minutes against 175.0 ± 48 minutes; p\<0.001). In spite of the fact that it took much time for the operation to be completed, the parameters concerning post-operative recovery were characterized by a rather high similarity rate between both cases. It indicates that neither the duration of hospitalization (8.7 ± 4.0 days versus 8.6 ± 4.1 days) nor the period of mechanical ventilation (112.2 ± 56.9 min versus 116.9 ± 64.7 min) had a statistical significance. Besides, one more thing needs to be highlighted regarding the lack of statistically significant difference in terms of ICU admission, hospitalization period (8.7 ± 4.0 days versus 8.6 ± 4.1 days), or mechanical ventilation time (112.2 ± 56.9 min versus 116.9 ± 64.7 min). It also needs to be pointed out that in regards to the secondary results obtained in connection with the occurrence of postoperative complications, need for transfusion, pain, or mortality, virtually the same picture was observed. Thus, summarizing all findings of this study, one can say that, with the use of an optimized ERACS protocol, aimed at achieving rapid extubation and creating standardized treatment algorithms, MICS-CABG is considered to be a relatively safe and very effective therapy option for patients compared to traditional off-pump CABG surgeries (Saad et al., 2026). Within the context of the current study comparing minimally invasive anterior minithoracotomy with full median sternotomy CABG, differences in surgical exposure, operative stress, and possible differences in hemodynamic stability may theoretically affect renal perfusion patterns. Thus, assessment of renal outcomes following these two techniques is of interest in determining whether surgical technique affects postoperative renal function. Of the 881 studies that were found, 26 satisfied the requirements for qualifying. The total number of patients in this study was 7,556. Positive procedural safety and early recovery profiles for minimally invasive techniques are reported by several single-center cohorts and systematic reviews, which support these findings (Sef et al., 2024). Thakar et al. showed that postoperative renal impairment is independently linked to higher mortality and longer hospital stays, and they created a clinical risk score for predicting AKI following heart surgery. This study shows that in addition to improving its clinical utility, a score is reliable and accurate in predicting ARF following open heart surgery and can aid in the development of upcoming ARF clinical studies(Thakar et al., 2005). Nonetheless, the incidence of early AKI in both minimally invasive and conventional CABG has not been investigated in any major prospective study. Renal failure is not the primary outcome measure in most trials; rather, they investigate overall postoperative outcomes such as hospital stay, wound complications, or revascularization success. For example, MICS-CABG and conventional CABG showed similar revascularization success and therapeutic outcomes in a recent retrospective study conducted at a single institution, which included patients with Type 2 diabetes and CAD; but it did not offer data on AKI incidence(Guangxin et al., 2024). Additionally, postoperative AKI is linked to higher morbidity, according to clinical trials. For example, compared to patients without AKI, those who experienced renal failure following CABG had longer perfusion and cross-clamp periods, longer hospital admissions, and longer mechanical breathing(Slaughter et al., 2025). Several factors associated with the occurrence of CSA-AKI in patients undergoing CABG have been examined by Oosterom-Eijmael et al. (2026). Based on the research conducted by the team, the features of AKI after a heart surgery include decreased renal perfusion, inflammation associated with cardiopulmonary bypass, ischemia/reperfusion injury, hemolysis, and perioperative hypotension. Furthermore, Oosterom-Eijmael et al. highlight that the renal medulla becomes prone to hypoxia during bypass procedure which leads to tubular injury and dysfunction of kidneys. It should be noted that, based on the study conducted by Oosterom-Eijmael et al., serum creatinine cannot be considered as an effective marker for detecting AKI since it demonstrates an elevated level only in a later phase. Therefore, biomarkers, such as NGAL, KIM-1, and TIMP-2, can be used for diagnosing AKI. Besides, it is possible to use minimally invasive methods of cardiac surgery to decrease the degree of inflammation and tissue injury(Oosterom-Eijmael et al., 2026). In their retrospective cross-sectional study, Sljivo et al. (2025) compared perioperative parameters and the characteristics of minimally invasive procedures between Minimally Invasive Coronary Artery Bypass Grafting (MICS-CABG) through left anterior thoracotomy and the more common conventional open-heart surgical technique of median sternotomy (OPEN-CABG). The researchers studied specific clinical indicators among the two groups in order to assess the effectiveness of a minimally invasive approach to accessing the chest cavity. The results from the statistical analysis showed that the procedure time was shorter when MICS-CABG was performed, being on average 2.5 hours rather than 3.5 hours in the open-heart group. Additionally, the minimally invasive group exhibited decreased ventilation time after surgery at 11.0 hours as opposed to 14.0 hours in the control group.However, the study also emphasized a remarkable decrease in hemodynamic burden, which meant that patients undergoing the MICS-CABG procedure required inotropic support far less often, either at lower (50.4% vs 62.8%, P = 0.043) or medium doses (4.0% vs 16.0%, P = 0.001). In addition, fewer wound and infection-related complications occurred in patients undergoing thoracotomy surgery than suffered from the extensive bone injury that occurs during the open sternotomy procedure. This research provides crucial information about how the MICS-CABG clinical setting helps speed up patient recovery and offers excellent vascular/structural protection(Sljivo et al., 2025). The paper by Ashenhurst et al. (2024) covers the immediate and long-term impacts of less invasive surgeries performed during coronary artery bypass surgery. The authors compare minimally invasive approaches and standard median sternotomy CABG from perspectives of the surgical technique itself, patient postoperative management, and long-term outcomes. From the viewpoint of the surgical approach, a minimally invasive operation via left minithoracotomy is a less invasive method when compared to CABG surgery with a standard surgical technique. Postoperatively, patients who underwent minimally invasive procedures experienced lesser pain, suffered from fewer complications associated with surgery wounds, shorter hospitalizations, and faster recovery periods. Long-term follow-up information described in this review shows that MICS CABG provides satisfactory rates of patency, survival, and incidences of adverse events(Christine et al., 2024). Kar et al. (2021) conducted a prospective observational study designed to assess the use of urinary NGAL as a prognostic biomarker for AKI against the known serum creatinine parameters. The patients included in the clinical trial were 42 patients who were in optimal renal condition before operation and who underwent CABG procedures supported by CPB. The levels of urinary NGAL were quantitatively tested pre-operatively and six hours after the start of CPB. According to the results obtained by the team, nearly 19% of the subjects under observation experienced post-operative AKI. Importantly, despite the time delay associated with the use of conventional serum creatinine parameters, which was estimated at 24 to 48 hours, urinary NGAL rose significantly within just 6 hours after CPB in the absence of any significant alterations in blood work results. The study concludes that urinary NGAL is an efficient and reliable early predictor of ischemic AKI in adults. Since it proves that reliance on slow metabolic changes reflected in creatinine is ineffective for the purpose of detecting AKI in its early stages(Kar et al., 2021). Teman et al. (2021)undertook a multicenter evaluation of MICS compared to conventional open heart surgery, taking into account both patient outcomes and medical expenses. They discovered that MICS-CABG led to similar occurrences of serious complications (such as strokes and mortality), but it decreased the duration of ICU stay and lowered the requirement for blood transfusions by 50 percent. Crucially, they discovered that MICS did not cost more than traditional surgery, even when the advantages of recovery were taken into consideration. This article helps to justify your study because it demonstrates that MICS is a feasible, cost-effective technique that may lessen the occurrence of early AKI by minimizing perioperative stressors. Reduced transfusions will protect the kidney from extreme iron nephrotoxicity(Investigators for the Virginia Cardiac Services Quality et al., 2021). Flaih et al. (2025) performed a matched cohort study on the clinical impact of surgical urgency in relation to MICS-CABG procedures. While there is abundant literature available on the effect of emergency surgery on the results of open procedures, Flaih et al. examined the specific effects of surgical urgency on MICS procedures. Clinical findings revealed that patients who underwent an urgent MICS-CABG procedure were at increased risk of post-operative renal impairment, acute kidney injury, and prolonged dependency on vasopressors as compared to patients who had undergone elective procedures. The authors attributed these risks to hemodynamic instability prior to surgery, acute cardiac ischemia, and the insufficient time available to optimize the pre-operative renal autoregulation of patients before proceeding to surgery. Flaih et al. emphasize that surgical urgency is a highly significant confounding variable that should be controlled or taken into account when comparing minimally invasive ports to conventional sternotomy(Abdullah et al., 2025). Sellin et al. (2024) performed a comparative study to investigate the renal effects among patients who underwent minimal invasive total coronary revascularization with anterior minithoracotomy (TCRAT) and full median sternotomy CABG. However, in both groups, after matching criteria have been used, 170 subjects have been included in the study. The serum creatinine levels, estimated glomerular filtration rate, urea level, incidences of acute renal failure, and need for hemodialysis were considered. However, despite increased cardiopulmonary bypass time and increased cross-clamp time in the group of TCRAT, no differences were found in the incidence of postoperative renal complications in comparison with the group where FS was applied. Moreover, hospital stay duration was significantly shorter in the minimal invasive technique group(Sellin et al., 2024). Although there is a wealth of information regarding the risk factors and results of AKI following traditional CABG, there is still a lack of specific studies on the impact of surgical technique on early kidney failure. None of the have prospectively evaluated the frequency of early AKI between minimally invasive anterior minithoracotomy and conventional median sternotomy in on-pump CABG patients, and the majority of studies on cardiac surgical-induced AKI do not differentiate between less invasive and conventional sternotomy. This is an important gap in the literature because results about variations in early AKI frequency between techniques may have consequences for perioperative care and surgical choice-making. In conclusion, the research now in publication clearly shows that AKI following CABG is common, connected to a number of procedural and patient risk factors, and related with unfavorable results. The significance of the planned prospective trial is highlighted by the lack of direct data comparing early AKI rates between minimally invasive anterior minithoracotomy and traditional median sternotomy CABG. # CHAPTER 3 {#chapter-3 .unnumbered} ## OBJECTIVES 1. To determine and compare the frequency of early acute kidney injury (AKI) in patients undergoing on-pump coronary artery bypass grafting (CABG) via Minimally invasive anterior minithoracotomy versus Conventional full median sternotomy. 2. To evaluate how both surgical groups\' serum creatinine, eGFR urea and nitrogen levels changed throughout the first 48 hours after surgery. ## HYPOTHESIS **Null Hypothesis (H₀):** There is **no difference** in the frequency of early AKI between patients undergoing on-pump CABG via minimally invasive and conventional cardiac surgery. **Alternative Hypothesis (H₁):** There is a **significant difference** in the frequency of early AKI between patients undergoing on-pump CABG via minimally invasive and conventional cardiac surgery. **\ ** ## OPERATIONAL DEFINITIONS **Early Acute Kidney Injury (AKI):** Early acute kidney injury is define as in the first 48 to 72 hours after on pump CABG, by the KDIGOinstructions: **Stage 1:**serum creatinine Increase by ≥0.3 mg/dL within 48 hoursOR 1.5--1.9 times increase from baseline; Urine output \<0.5 mL/kg/hr for 6--12 hours. **Stage 2:**increase in serum creatinine by 2.0--2.9 times from baselineOR Urine output \<0.5 mL/kg/hr for ≥12 hours **Stage 3:** increase in serum creatinine by 3.0 times from baseline OR Serum creatinine ≥4.0 mg/Dl OR Dialysis ;Urine output \<0.3 mL/kg/hr for ≥24 hours OR Anuria for ≥12 hours (Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group, 2012). **On-Pump Coronary Artery Bypass Grafting (CABG):** A heart surgery to bypass blocked coronary arteries using a heart-lung machine(Thakare et al., 2023) **Minimally Invasive Anterior Minithoracotomy CABG:** This procedure is performed with a small incision on the anterior chest wall without the use of a median sternotomy.(Kayatta et al., 2018). **Conventional Full Median Sternotomy CABG:** A complete median sternotomy in which incision done through the subcutaneous tissues all the way to the sternum(Papakonstantinou, 2020). **Serum Creatinine:** Based on variations from baseline preoperative readings, this biochemical indicator of kidney function, expressed in mg/dL, is used to diagnose and stage AKI. **Serum urea:** A measure of protein metabolism waste in the blood, where the normal range is between 2.5 and 7.8 mmol/L. High levels of this compound can be a symptom of kidney disease or dehydration, while low levels can be a symptom of severe liver disease or malnutrition. # CHAPTER 4 {#chapter-4 .unnumbered} # MATERIAL AND METHODS {#material-and-methods .unnumbered} 1. []{#_Toc230618476 .anchor}**Study Design:** It is a Comparative cross-sectional study**.** 2. []{#_Toc230618477 .anchor}**Study Settings:** This study is multi centered study (Umar hospital and cardiac center, Gulab Devi chest Hospital). 3. []{#_Toc230618478 .anchor}**Duration of Study:** The study duration was about 4 months. 4. []{#_Toc230618479 .anchor}**Sample Size:** There was 150patientsusedinthis study. 𝑛= 2𝜎^2^(𝑍𝑎/2+𝑍𝛽)^2^ > 𝑑2 ![](media/image2.jpeg){width="5.076388888888889in" height="3.9583333333333335in"} 5. []{#_Toc230618480 .anchor}**Sampling Technique**: Convenient sampling technique was utilized. Unless the goal was accomplished, every patient who qualified for the investigation was accepted. ## Sampling Selection: 1. []{#_Toc230618482 .anchor}**Inclusion Criteria:** ```{=html} ``` 1. Patients aged ≥18 years. 2. Patients undergoing elective on-pump CABG. 3. Surgery performed via minimally invasive anterior minithoracotomy or conventional median sternotomy. 4. Availability of baseline and 48--72 hour postoperative Renal Function Test Values. 1. []{#_Toc230618483 .anchor}**Exclusion Criteria:** ```{=html} ``` 1. Patients undergoing off-pump CABG**.** 2. Patients performed with multiple cardiac procedures (e.g., CABG with > valve surgery). 3. Patients with pre-operative dialysis-dependent renal failure**.** 4. Patients with preoperative acute kidney injury**.** 5. Incomplete medical records. **\ ** ## ETHICAL CONSIDERATIONS **(Where needed for clinical studies, animal study, experimental study)** []{#_Toc230618485 .anchor}The rules and regulations set by the ethical committee of university of Lahore will be followed while conducting the research and the rights of the research participants will be respected. - []{#_Toc230618486 .anchor}Written informed consent (attached) will be taken from all the participants. - []{#_Toc230618487 .anchor}All information and data collection will be kept confidential. - []{#_Toc230618488 .anchor}Participants will remain anonymous throughout the study. - []{#_Toc230618489 .anchor}The subjects will be informed that there are no disadvantages or risks on the procedure of the study. - []{#_Toc230618490 .anchor}They will also be informed that they will be free to withdraw at any time during the process of the study. - Mention if there will be any known risks associated with this research. - Mention if there will be benefits to the participant that would result from their participation in this research. - We will do everything we can to protect your privacy. Your identity will not be revealed in any publication resulting from this study. - Your participation in this research study is voluntary. You may choose not to participate and you may withdraw your consent to participate any time. You will not be penalized in any way should you decide not you participate or to withdraw from this study. 1. **\ ** ## 4.8 DATA COLLECTION PROCEDURE {#data-collection-procedure .unnumbered} After obtaining ethical approval, eligible patients undergoing on-pump CABG were identified. Baseline demographic data and preoperative serum creatinine values were recorded from hospital records. Postoperative serum creatinine, blood urea, blood urea nitrogen (BUN), and urine output values within 48--72 hours will be documented. Patients were assessed for development of early AKI according to KDIGO criteria(Schiefer et al., 2023). All data were recorded on a structured proforma and entered into SPSS for statistical analysis. **\ ** ## DATA ANALYSIS PROCEDURE Data were analyzed by using SPSS version 27. Continuous variables were presented as mean ± standard deviation, and categorical variables were presented as frequencies and percentages. The frequency of early AKI between minimally invasive and conventional sternotomy groups was compared by using the Chi-square test. Independent sample t-test were used for quantitative variables withnormal distributed data and for non normal distributed data Mann-whietny U test were used. A p-value ≤ 0.05 were considered statistically significant. # CHAPTER 5 {#chapter-5 .unnumbered} # RESULTS {#results .unnumbered} **Baseline Demographic and Clinical Characteristics** A total of one hundred and fifty elective on-pump CABG cases were enrolled in this study. These participants were randomly allocated into two groups, whereby seventy-five patients were selected for each group: namely MICS-CABG group and conventional median sternotomy group. The demographic pattern of the majority of patients enrolled in the study was males (88.7%) aged over fifty years (79.3%), as shown in Tables 5.1 and Figure 5.1. Hypertension was the most common co-morbid factor that was present in almost all patients (98.7%). Diabetes mellitus was noted in 28.7% of patients, while current and former smokers made up 26.7% of patients. Chronic kidney disease was recorded in 9.3% of patients. No statistical significance was seen between the two groups with respect to the distribution of gender, age group, body mass index, diabetes mellitus, hypertension, chronic kidney disease, smoking, and left ventricular ejection fraction (all p\>0.05). []{#_Toc230618411 .anchor}**Table 5. 1: Comparison of Baseline Characteristics** ---------------------------------------------------------------------------------- Variable Minimally Conventional Statistical p-value Significance Invasive Sternotomy Test (n=75) (n=75) -------------- ------------ --------------- ------------- --------- -------------- Male Gender 67 (89.3%) 66 (88.0%) Chi-square 1.000 No Diabetes 23 (30.7%) 20 (26.7%) Chi-square 0.718 No Mellitus Hypertension 75 (100%) 73 (97.3%) Chi-square 0.476 No Chronic Kidney 5 (6.7%) 9 (12.0%) Chi-square 0.399 No Disease Smoking 18 (24.0%) 22 (29.3%) Chi-square 0.580 No Age \>50 years 59 (78.7%) 60 (80.0%) Chi-square 1.000 No Age 31--50 14 (18.7%) 15 (20.0%) Chi-square 1.000 No years Age 20--30 2 (2.7%) 0 (0.0%) Chi-square 0.476 No years BMI 2 (2.7%) 1 (1.3%) Chi-square 1.000 No Underweight BMI Normal 13 (17.3%) 20 (26.7%) Chi-square 0.237 No Weight BMI Overweight 40 (53.3%) 32 (42.7%) Chi-square 0.253 No BMI Obese 0 (0.0%) 0 (0.0%) Chi-square 1.000 No LVEF 41--54% 39 (52.0%) 45 (60.0%) Chi-square 0.411 No LVEF \<40% 13 (17.3%) 11 (14.7%) Chi-square 0.824 No ---------------------------------------------------------------------------------- Despite this, quantitatively significant changes were observed among two baseline variables that were continuous, as indicated in Table 5.2. The starting point serum creatinine levels of the Minimally Invasive category (1.00 ± 0.25 mg/dL) as well as the Conventional category (1.16 ± 0.37 mg/dL; t(148) = -3.151, p = 0.002) differed little but statistically significantly. In a comparable manner similar to the Conventional category (71.04 ± 24.08 mL/min/1.73m²; U = 3476.5, p = 0.013), the Minimally Invasive group presented with a significantly greater average eGFR (80.37 ± 21.75 mL/min/1.73m²). But for both categories, both variables stayed within clinically acceptable boundaries and did not indicate renal impairment in accordance with the study\'s criteria for exclusion. **\ ** []{#_Toc230618412 .anchor}**Table 5. 2 Comparison of Quantitative Variables Between the Study Groups** ------------------------------------------------------------------------------------------------ Variable Minimally Conventional Statistical Test p-value Significance Invasive Sternotomy Test Statistic Mean ± SD Mean ± SD ----------------- ----------- -------------- -------------- ----------- --------- -------------- Baseline 1.00 ± 0.25 1.16 ± 0.37 Independent t(148) = 0.002 Yes Creatinine t-test -3.151 (mg/dL) Baseline eGFR 80.37 ± 21 71.04 ± 24 Mann-Whitney U U = 3476.5 0.013 Yes (mL/min/1.73m²) LVEF (%) 50.80 ± 9.7 49.39 ± 8.4 Independent t(148) = 0.344 No t-test 0.950 Preoperative 13.50 ± 1.4 13.19 ± 1.5 Independent t(148) = 0.200 No Hemoglobin (g/dL) t-test 1.287 ------------------------------------------------------------------------------------------------ **Note.** Categorical variables compared using Pearson chi-square or Fisher\'s exact test. Continuous variables compared using independent samples t-test. p\< .05 considered statistically significant while using mannwhitney U test for baseline eGFR considered statistically significant. []{#_Toc230618413 .anchor}**Table 5. 3; Frequency of Age distribution range (N=150)** -------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ----------- -------------- ------------ -- ------------------ ------------ \>50 years 119 79.3 79.3 79.3 31--50 29 19.3 19.3 98.6 years 20--30 2 1.3 1.3 99.9 years -------------------------------------------------------------------------- **Note:** This table shows majorities of the participants were above the age of 50 years and about 19.3 percent were between 31 to 50 years and only 1.3 percent patients present with between 20 to 30 years of age from the study parameter of n=150. ![C:\\Users\\HP\\AppData\\Local\\Temp\\a0c1e77d-3955-4ef1-b1bc-be1b21d87fcb_AKI_Analysis_Results.zip.fcb\\01_Figures\\Descriptive\\DESC_Q02_Age_Range.png](media/image3.png){width="4.907638888888889in" height="3.4680555555555554in"} []{#_Toc230618431 .anchor}**Figure 5. 1 Age range distribution of the study population(N=150)** **Note:** above 5.1 figure shows age range distribution of the population in which majority of the patients was above 50 years about 79.3%, while in the category of 31-50 was 19.3% and only 1.3 % were fall in 20-30 years age catergory. []{#_Toc230618414 .anchor}**Table 5. 4:FREUQNCY DISTRIBUTION OF GENDER (n=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ---------- -------------- ------------ ----------------- ---------------- Male 133 88.7 88.7 88.7 Female 17 11.3 11.3 100.0 ------------------------------------------------------------------------- **Note:** This table shows majority were the male from the sample population of which about 88.7% (n=133) and only 11.3% (n=17) were the female. ![C:\\Users\\HP\\AppData\\Local\\Temp\\da598e19-4c9a-4fe3-9509-939ac1b29f50_AKI_Analysis_Results.zip.f50\\01_Figures\\Descriptive\\DESC_Q03_Gender.png](media/image4.png){width="4.957638888888889in" height="2.6840277777777777in"} []{#_Toc230618432 .anchor}**Figure 5. 2 Gender distribution in the study population (N=150)** **Note:** The figure represents a total of 150 participants out of which 11.3% were female and 88.7% were male. **\ ** []{#_Toc230618415 .anchor}**Table 5. 5: Frequency distribution of BMI category (n=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent Cumulative (%) (%) ----------------- ------------- ----------- -------------- -------------- Underweight 3 2.0 2.0 2.0 (\<18.5) Normal 33 22.0 22.0 24.0 (18.5--24.9) Overweight 72 48.0 48.0 72.0 (25--29.9) Obese (\>=30) 0 0.0 0.0 72..0 ------------------------------------------------------------------------- **Note:** Table 5.5 shows frequency distribution of BMI. According to this 2 percent patients were included in underweight category, 22 percent were in normal weight, while majorities in overweight with 48 percent and there was no obese patient were seen from the sample population. ![C:\\Users\\HP\\AppData\\Local\\Temp\\1841636f-740c-4444-9ec2-5d923f2ee07c_AKI_Analysis_Results.zip.07c\\01_Figures\\Descriptive\\DESC_Q04_BMI_Category.png](media/image5.png){width="5.05625in" height="2.76875in"} []{#_Toc230618433 .anchor}**Figure 5. 3 BMI category distribution** **Note:** This figure shows BMI divides into four categories. Only 2% of study population falls in underweight category with less then 18.5 BMI,in normal range only 22% of population falls while majority of them are in overweight category with frequency f 48% and there are no one in above 30 range of BMI. []{#_Toc230618416 .anchor}**Table 5. 6: Frequency distribution of diabetes mellitus (N=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ---------- -------------- ------------ ----------------- ---------------- Yes 43 28.7 28.7 28.7 No 107 71.3 71.3 100.0 ------------------------------------------------------------------------- **NOTE:** According to this about 28.7 percent patients present with diabetes and majorities of them about 71.3 percent were non diabetic. ![C:\\Users\\HP\\AppData\\Local\\Temp\\8e70c814-75eb-4a2b-b2d2-14c019c73aea_AKI_Analysis_Results.zip.aea\\01_Figures\\Descriptive\\DESC_Q05_Diabetes.png](media/image6.png){width="5.588888888888889in" height="3.0840277777777776in"} []{#_Toc230618434 .anchor}**Figure 5. 4 diabetes mellitus distribution in study population** **Note:** There were 28.7% of patients diabetic and 713% with no dibetes. []{#_Toc230618417 .anchor}**Table 5. 7: Frequency distribution of hypertension (n=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ---------- -------------- ------------ ----------------- ---------------- Yes 148 98.7 98.7 98.7 No 2 1.3 1.3 100.0 ------------------------------------------------------------------------- **Note:** there were 98.7 percent sample population seen with hypertensive history and only 1.3 percent present with no hypertension. ![C:\\Users\\HP\\AppData\\Local\\Temp\\a1a08543-4785-4e0a-b6e9-520030cf8e6e_AKI_Analysis_Results.zip.e6e\\01_Figures\\Descriptive\\DESC_Q06_Hypertension.png](media/image7.png){width="4.584027777777778in" height="3.7875in"} []{#_Toc230618435 .anchor}**Figure 5. 5: Hypertension distribution in sample population** **Note:** There were 98.7 percent population from the sample shows with hypertension and only 2 percent with no hypertension. ***\ *** []{#_Toc230618418 .anchor}**Table 5. 8 frequency distribution of chronic kidney disease (CKD) (N=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ---------- -------------- ------------ ----------------- ---------------- Yes 14 9.3 9.3 9.3 No 136 90.7 90.7 100.0 ------------------------------------------------------------------------- **\ ** **NOTE:** This table shows patients present with CKD were about n=14 and non CKD n=136. ![C:\\Users\\HP\\AppData\\Local\\Temp\\5b85f9e2-e0e3-4ac0-a7d7-6d724c499a5b_AKI_Analysis_Results.zip.a5b\\01_Figures\\Descriptive\\DESC_Q07_CKD.png](media/image8.png){width="3.620833333333333in" height="2.990972222222222in"} []{#_Toc230618436 .anchor}**Figure 5. 6 chronic kidney disease in sample population.** **Note:** This figure shows that majority of the population(90.7%) from the sample size presented with no CKD and only 9.3% having CKD. []{#_Toc230618419 .anchor}**Table 5. 9: frequency distribution of smoking status (n=150)** ------------------------------------------------------------------------- Category Frequency (n) Percent (%) Valid Percent (%) Cumulative (%) ---------- --------------- ------------- ------------------- ------------ Yes 40 26.7 26.7 26.7 No 110 73.3 73.3 100.0 ------------------------------------------------------------------------- **Note:** this table shows that only 26.7 % patients with smoking history and 73.3% with no smoking history. ![C:\\Users\\HP\\AppData\\Local\\Temp\\071c0766-c14f-4517-b553-0a56addb6b38_AKI_Analysis_Results.zip.b38\\01_Figures\\Descriptive\\DESC_Q08_Smoking.png](media/image9.png){width="2.448611111111111in" height="2.0229166666666667in"} []{#_Toc230618437 .anchor}**Figure 5. 7: smokig status distribution** **Note:**There were 73.3% patients with nonsmoking and only 26.7% were smoking history. **Descriptive Statistics of Continuous Variables** []{#_Toc230618420 .anchor}**Table 5. 10: Descriptive Statistics of baseline Serum Creatinine Statistics (mg/dL) --- Total Sample and by Surgical Group** ------------------------------------------------------------------------------------------------------------------------------ Variable Group N Mean SD Min Q1 (25th) Median Q3 (75th) Max Skewness ------------ -------------- --------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------- Baseline **Total **150** **1.08** **0.32** **0.50** **0.83** **1.07** **1.26** **1.88** **0.295** Creatinine (N=150)** (mg/dL) MICS-CABG 75 1.00 0.25 0.50 0.84 0.99 1.11 1.63 --- (n=75) Conventional 75 1.16 0.37 0.50 0.93 1.17 1.37 1.88 --- (n=75) ------------------------------------------------------------------------------------------------------------------------------ **Note:** The above table shows an in-depth analysis of the preoperative serum creatinine concentrations for each surgical group as well as the combined group (N = 150). Mean preoperative serum creatinine concentration for all participants in the study was 1.08 ± 0.322 mg/dL with the median value at 1.07 mg/dL, due to slightly positive skewness at 0.295. When the outcomes were grouped according to the surgeryt method, the mean level of serum creatinine before the procedure was comparatively greater in traditional surgery (1.16 ± 0.365 mg/dL) than in minimally invasive surgery (0.999 ± 0.250 mg/dL). ![C:\\Users\\HP\\AppData\\Local\\Temp\\0e9b64be-79fb-4259-8549-05a6c6ac1074_AKI_Analysis_Results.zip.074\\01_Figures\\Descriptive\\DESC_Q09_Baseline_Creatinine_Histogram.png](media/image10.png){width="5.452083333333333in" height="2.261111111111111in"} []{#_Toc230618438 .anchor}**Figure 5. 8 Baseline Serum Creatinine Distribution (N = 150).** **Note:** The mean baseline serum creatinine level from the total distribution (left graph) is 1.08 mg/dL (SD = 0.32). The range for the total baseline levels is about 0.5 -- 1.9 mg/dL with slight positive skewness, where the majority of participants lie in the interval of 0.9 to 1.3 mg/dL, shows almost normal kidney functions. When analyzing by surgical groups (right graph), it is evident that the distribution for the minimally invasive group is much more concentrated, with peaks at about 0.9 to 1.0 mg/dL compared to the conventional sternotomy group whose peak is at 1.1 to 1.2 mg/dL. []{#_Toc230618421 .anchor}**Table 5. 11: Descriptive Statistics of baslineeGFR (mL/min/1) --- Total Sample and by Surgical Group** ----------------------------------------------------------------------------------------------------------------------------------------- Variable Group N Mean SD Min Q1 (25th) Median Q3 (75th) Max Skewness ----------------- -------------- --------- ----------- ----------- ---------- ----------- ----------- ----------- ----------- ----------- Baseline eGFR **Total **150** **75.70** **23.34** **35.5** **59.05** **72.90** **92.88** **130.0** **0.217** (mL/min/1.73m²) (N=150)** MICS-CABG 75 80.37 21.75 36.8 62.00 79.90 96.00 130.0 --- (n=75) Conventional 75 71.04 24.08 35.5 51.10 67.10 88.50 118.8 --- (n=75) ----------------------------------------------------------------------------------------------------------------------------------------- **Note:** This table shows the combined basline of eGFRdistribution.according to this, the overall sample size had baseline mean eGFR 75.703 ± 23.341 mL/min/1.73m2 (Median = 72.9).When distributed by groups,Minimally Invasive group showed with higher baseline mean eGFR of 80.367 ± 21.749 mL/min/1.73m2 (Median = 79.9), whereas theConventional surgery group showed up with lower baseline of 71.039 ± 24.081 mL/min/1.73m2 (Median = 67.1). ![C:\\Users\\HP\\AppData\\Local\\Temp\\dc81f6df-d6ae-4d65-905c-3316f6abba15_AKI_Analysis_Results.zip.a15\\01_Figures\\Descriptive\\DESC_Q10_Baseline_eGFR_Histogram.png](media/image11.png){width="5.915972222222222in" height="2.453472222222222in"} []{#_Toc230618439 .anchor}**Figure 5. 9: *Baseline eGFR Distribution (N = 150).*** ***Figure 4.9* Note:** As shown in overall distribution chart, the average estimated Baseline Glomerular Filtration Rate was 75.70 mL/min/1.73m² (SD = 23.34), vary roughly from 35 and 130 mL/min/1.73m². It clearly shown in the chart that the overall distribution of the eGFR values is slightly towards left-skewed, with the peak value at 60-70 mL/min/1.73m². Most of the patients belonged to the 52.36 - 99.04 mL/min/1.73m² interval, which means that they generally had a slightly reduced level of renal function. In terms of the surgery group, the Minimally Invasive group (blue color) had the distribution of eGFR skewed toward higher values, with the peak value at 85-90 mL/min/1.73m². The Conventional sternotomy group (red color) had a more wide distribution concentrated mostly at 60-75 mL/min/1.73m² values. []{#_Toc230618422 .anchor}**Table 5. 12: Descriptive Statistics of LVEF(%) --- Total Sample and by Surgical Group** -------------------------------------------------------------------------------------------------------------------------------- Variable Group N Mean SD Min Q1 (25th) Median Q3 (75th) Max Skewness ---------- -------------- --------- ----------- ---------- ---------- ----------- ----------- ----------- ---------- ----------- LVEF (%) **Total **150** **50.09** **9.09** **28.2** **43.45** **50.25** **56.18** **75.0** **0.200** (N=150)** MICS-CABG 75 50.80 9.70 28.4 43.20 50.70 59.40 75.0 --- (n=75) Conventional 75 49.39 8.43 28.2 42.90 50.00 55.00 67.6 --- (n=75) -------------------------------------------------------------------------------------------------------------------------------- **Note:**Values shown as Mean, SD, Median (50th percentile), Q1 (25th percentile), Q3 (75th percentile). Skewness reported for total sample only. MICS-CABG = Minimally Invasive Cardiac Surgery-CABG. Bold rows = total sample statistics ![C:\\Users\\HP\\AppData\\Local\\Temp\\7a958832-52a0-4051-8ef2-444526083632_AKI_Analysis_Results.zip.632\\01_Figures\\Descriptive\\DESC_Q11_LVEF_Percent_Histogram.png](media/image12.png){width="5.491666666666666in" height="2.276388888888889in"} []{#_Toc230618440 .anchor}**Figure 5. 10: Baseline Left Ventricular Ejection Fraction (LVEF) Distribution (N =** ***Note:*** The left side of the chart with whole population distribution represents with a mean baseline LVEF value of 50.09% (SD = 9.09) with values distributed between 28% and 75%. The overall distribution shows a slight skewness to the right, with maximum frequency observed in the 48%-52% range. The most of the study subjects were found to have baseline LVEF values falling within the range 41.01% and 59.18%, which means that the study involved subjects who had mildly reduced to low-normal function of the left ventricle, which was consistent with the type of surgery the subjects had. In terms of baseline distribution based on the two surgical groups (right chart), while both the Minimally Invasive group (in blue) and the Conventional sternotomy group (in red) have similar ranges (48%-52%), the former has a wider range extending up to 60%-75% LVEF while the latter\'s range extends up to 40%-55%. []{#_Toc230618423 .anchor}**Table 5. 13: Descriptive Statistics of preophemoglobin(g\\dl) --- Total Sample and by Surgical Group** --------------------------------------------------------------------------------------------------------------------------------------- Variable Group N Mean SD Min Q1 (25t) Median Q3 (75th) Max Skewness ------------------ -------------- --------- ----------- ---------- --------- ----------- ----------- ----------- ---------- ----------- PreopHaemoglobin **Total **150** **13.35** **1.49** **9.4** **12.30** **13.40** **14.10** **16.9** **0.238** (g/dL) (N=150)** MICS-CABG 75 13.50 1.46 10.1 12.50 13.40 14.50 16.6 --- (n=75) Conventional 75 13.19 1.51 9.4 12.10 13.00 14.00 16.9 --- (n=75) --------------------------------------------------------------------------------------------------------------------------------------- **Note :**Values shown as Mean, SD, Median (50th percentile), Q1 (25th percentile), Q3 (75th percentile). Skewness reported for total sample only. MICS-CABG = Minimally Invasive Cardiac Surgery-CABG. Bold rows = total sample statistics ![C:\\Users\\HP\\AppData\\Local\\Temp\\658aad48-e8b1-4c45-a399-2feb47acc45d_AKI_Analysis_Results.zip.45d\\01_Figures\\Descriptive\\DESC_Q11b_LVEF_Category.png](media/image13.png){width="3.8555555555555556in" height="2.7263888888888888in"} []{#_Toc230618441 .anchor}**Figure 5. 11: Distribution of LVEF Categories Among Study population (N = 150)** **Note:**Majority of the sample populationshowed up with moderately decreased LVEF (41-54%, n = 84; 56%), and 16% (n = 24) had high LVEF (LVEF \<40%). None of the patients had preserved LVEF (≥55%). All the participants had systolic dysfunction to some extent. ![C:\\Users\\HP\\AppData\\Local\\Temp\\76048f26-e6ff-4986-b169-b63b037d1565_AKI_Analysis_Results.zip.565\\01_Figures\\Descriptive\\DESC_Q12_Preop_Haemoglobin_Histogram.png](media/image14.png){width="5.639583333333333in" height="2.3381944444444445in"} []{#_Toc230618442 .anchor}**Figure 5. 12 *Preoperative Haemoglobin Distribution (N = 150).*** **Note:**Most individuals had preoperative hemoglobin levels between 11.86 and 14.84 g/dL, with an average of 13.35 g/dL (SD = 1.49). The patients in the Minimally invasive group had relatively higher levels of haemoglobin. ![C:\\Users\\HP\\AppData\\Local\\Temp\\72f60972-e02d-4de1-9429-e9b07cef8c3e_AKI_Analysis_Results.zip.c3e\\01_Figures\\Descriptive\\DESC_Q13_Surgical_Approach.png](media/image15.png){width="4.522222222222222in" height="2.2569444444444446in"} []{#_Toc230618443 .anchor}**Figure 5. 13 Distribution of Surgical Approach from Sample Population** **Note:**From the both groups, the Minimally Invasive (MICS-CABG) and the Conventional Median Sternotomy were equally distributed with a total number of 75 participants sample size of each. []{#_Toc230618424 .anchor}**Table 5. 14:Descriptive Summary of Postoperative Renal parameters** ----------------------------------------------------------------------------------------------------------------------------------------- Variable Group N Mean SD Min Q1 (25th) Median Q3 (75th) Max Skewness ----------------- -------------- --------- ----------- ----------- ---------- ----------- ----------- ----------- ----------- ----------- Creatinine 24h **Total **150** **1.248** **0.377** **0.57** **1.00** **1.19** **1.50** **2.42** **0.652** (mg/dL) (N=150)** MICS-CABG 75 1.115 0.278 0.58 0.91 1.08 1.29 2.07 --- (n=75) Conventional 75 1.380 0.416 0.57 1.10 1.35 1.58 2.42 --- (n=75) Creatinine 48h **Total **150** **1.589** **0.966** **0.64** **1.04** **1.315** **1.73** **6.54** **2.539** (mg/dL) (N=150)** MICS-CABG 75 1.261 0.579 0.64 0.97 1.14 1.30 4.22 --- (n=75) Conventional 75 1.917 1.151 0.65 1.20 1.56 2.16 6.54 --- (n=75) Creatinine 72h **Total **150** **1.518** **0.908** **0.47** **0.98** **1.24** **1.68** **6.27** **2.394** (mg/dL) (N=150)** MICS-CABG 75 1.207 0.558 0.47 0.90 1.10 1.33 3.76 --- (n=75) Conventional 75 1.829 1.073 0.59 1.17 1.56 2.06 6.27 --- (n=75) eGFR 48h **Total **150** **58.13** **25.23** **8.4** **39.30** **57.60** **75.55** **118.9** **0.123** (mL/min/1.73m²) (N=150)** MICS-CABG 75 67.67 22.68 13.6 51.90 67.00 84.20 118.9 --- (n=75) Conventional 75 48.59 24.14 8.4 31.20 46.90 63.60 112.4 --- (n=75) BUN 48h (mg/dL) **Total **150** **21.65** **7.22** **9.3** **17.03** **21.25** **26.40** **43.4** **0.291** (N=150)** MICS-CABG 75 20.21 6.41 9.3 15.80 19.50 24.40 37.7 --- (n=75) Conventional 75 23.10 7.72 9.3 18.20 23.30 27.70 43.4 --- (n=75) Urea 48h (mg/dL) **Total **150** **46.34** **15.44** **20.0** **36.35** **45.45** **56.55** **92.9** **0.292** (N=150)** MICS-CABG 75 43.25 13.72 20.0 33.85 41.70 52.30 80.7 --- (n=75) Conventional 75 49.43 16.51 20.0 39.00 49.90 59.35 92.9 --- (n=75) ----------------------------------------------------------------------------------------------------------------------------------------- **Note:** Values shown as Mean, SD, Median (50th percentile), Q1 (25th percentile), Q3 (75th percentile). Skewness reported for total sample only. MICS-CABG = Minimally Invasive Cardiac Surgery-CABG. Bold rows = total sample statistics **Assessment of Normality (Shapiro-Wilk Test)** Before choosing whether parametric or non-parametric tests should be employed to make comparisons between groups, the assumption of normality was tested for all continuous variables individually in each group using the Shapiro-Wilk test (n=75 per group). For those which had p-value of \<0.05, indicating significant deviation from normality, Mann-Whitney U test was used, while for others that satisfied normality in both groups, an independent samples t-test was conducted (table 7.15). []{#_Toc230618425 .anchor}**Table 5. 15: Shapiro-Wilk Normality Test Results for Continuous Variables by Surgical Group** ------------------------------------------------------------------------------------------------------------------------ Variable MICS-CABG\ MICS-CABG\ MICS-CABG\ Conventional\ Conventional\ Conventional\ Test Used W-stat p-value Normal? W-stat p-value Normal? ------------------ ------------ ------------ ------------ --------------- --------------- --------------- -------------- Baseline 0.985 0.545 Yes 0.971 0.078 Yes Indep. t-test Creatinine (mg/dL) Baseline eGFR 0.985 0.502 Yes 0.947 0.003 No Mann-Whitney U (mL/min/1.73m²) LVEF (%) 0.984 0.456 Yes 0.993 0.966 Yes Indep. t-test PreopHaemoglobin 0.977 0.191 Yes 0.989 0.792 Yes Indep. t-test (g/dL) Creatinine 24h 0.959 0.016 No 0.984 0.461 Yes Mann-Whitney U (mg/dL) Creatinine 48h 0.653 \<0.001 No 0.787 \<0.001 No Mann-Whitney U (mg/dL) Creatinine 72h 0.661 \<0.001 No 0.810 \<0.001 No Mann-Whitney U (mg/dL) BUN 48h (mg/dL) 0.969 0.060 Yes 0.977 0.200 Yes Indep. t-test Urea 48h (mg/dL) 0.969 0.059 Yes 0.977 0.192 Yes Indep. t-test eGFR 48h 0.992 0.914 Yes 0.972 0.098 Yes Indep. t-test (mL/min/1.73m²) Creatinine Change 0.404 \<0.001 No 0.696 \<0.001 No Mann-Whitney U Δ48h Creatinine Ratio 0.412 \<0.001 No 0.608 \<0.001 No Mann-Whitney U 48h ------------------------------------------------------------------------------------------------------------------------ **Note:** Shapiro-Wilk test: p \< 0.05 represents thenon-normal distribution. Normal = Yes if p ≥ 0.05 (normal distribution). Mann-Whitney U test was used when either group was non-normal. Independent samples t-test was used when both groups were normally distributed. **Postoperative Renal Function Parameters** Serial postoperative serum creatinine was measured at 24, 48, and 72 hours for all 150 patients. BUN, serum urea, and eGFR at 48 hours were also recorded. Figures 4.14--4.23 show the distribution of these parameters for the total sample and by group. ![](media/image16.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618444 .anchor}**Figure 5. 14 Serum Creatinine Distribution at 24 Hours Postoperatively (N=150).** **Note:** This histogram represents in overall distribution sample Mean = 1.248 mg/dL (SD=0.377). while in MICS-CABG: Mean=1.115, Median=1.08 and Conventional: Mean=1.380, Median=1.35. Mann-Whitney U, p \< 0.001. ![](media/image17.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618445 .anchor}**Figure 5. 15: Serum Creatinine Distribution at 48 Hours Postoperatively (N=150).** **Note:** This histogram shows Mean = 1.589 mg/dL (SD=0.966) in overall sample distriution.whileMICS-CABG: Mean=1.261, Median=1.14. And for Conventional: Mean=1.917, Median=1.56. Mann-Whitney U, p \< 0.001. ![](media/image18.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618446 .anchor}**Figure 5. 16: Serum Creatinine Distribution at 72 Hours Postoperatively (N=150).** **Note:**The histogram showsMean = 1.518 mg/dL (SD=0.908) for whole participants. For MICS-CABG: Mean=1.207, Median=1.10. while for Conventional: Mean=1.829, Median=1.56. Mann-Whitney U, p \< 0.001. ![](media/image19.png){width="4.0in" height="3.303857174103237in"} []{#_Toc230618447 .anchor}**Figure 5. 17 *Low Urine Output Distribution in Study Population (N=150).*** **Note:** In this figure Low urine output observed in 16.0% MICS-CABG vs 24.0% Conventional patients. Overall prevalence = 20.0%. Chi-square p = 0.307 (not significant). ![](media/image20.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618448 .anchor}**Figure 5. 18 BUN at 48 Hours Distribution (N=150).** **Note:** The histogram represents witha total Mean = 21.65 mg/dL (SD=7.22), Median=21.25.while MICS-CABG: Mean=20.21, Median=19.50. andConventional: Mean=23.10, Median=23.30. Independent t-test, p = 0.014. ![](media/image21.png){width="4.0in" height="2.828640638670166in"} []{#_Toc230618449 .anchor}**Figure 5. 19: *BUN Category Distribution at 48 Hours (N=150).*** **Note:** Within 48h BUN category distribution from the sample population 74.7% of MICS-CABG and 53.3% of Conventional patients were shown. Chi-square = 7.912, p = 0.019. ![](media/image22.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618450 .anchor}**Figure 5. 20 *Serum Urea at 48 Hours Distribution (N=150).*** **Note:** Figure shows total Mean = 46.34 mg/dL (SD=15.44), Median=45.45.while MICS-CABG: Mean=43.25, Median=41.70.For Conventional: Mean=49.43, Median=49.90. Independent t-test, p = 0.014. ![](media/image23.png){width="4.0in" height="2.828640638670166in"} []{#_Toc230618451 .anchor}**Figure 5. 21 *Urea Category Distribution at 48 Hours (N=150).*** **Note:** According to figure 5..21 from the sample size ,25.3% of Conventional surgery participants represents with Urea \> 60 mg/dL and 13.3% of MICS-CABG paaticipants were represents with Urea \> 60 mg/dL. Chi-square = 8.186, p = 0.017. ![](media/image24.png){width="5.5in" height="2.2822430008748906in"} []{#_Toc230618452 .anchor}**Figure 5. 22eGFR at 48 Hours Distribution (N=150).** **Note:** In the histogram Total Mean = 58.13 mL/min/1.73m² (SD=25.23), Median=57.60 represents the overall sample distribution for eGFR.On right side from two groups, MICS CABG represents, Mean=67.67, Median=67.00.and Conventional shows with Mean=48.59, Median=46.90. Independent t-test, p \< 0.001. ![](media/image25.png){width="4.0in" height="2.828640638670166in"} []{#_Toc230618453 .anchor}**Figure 5. 23*eGFR Category Distribution at 48 Hours (N=150).*** **Note:** Above figure shows 44.0% MICS-CABG vs 17.3% Conventional maintained eGFR ≥60 mL/min/1.73m². 74.7% Conventional vs 40.0% MICS-CABG had eGFR\< 60. Chi-square = 18.556, p \< 0.001. **Comparison of Serial Postoperative Renal Parameters Between Groups** Following analysis represents the inferential comparison of postoperative renal parameters between the two surgical groups. Normality-based test selection was applied as determined by Shapiro-Wilk results in Table 5.16. []{#_Toc230618426 .anchor}**Table 5. 16: Comparison of Serial Postoperative Renal Parameters** ------------------------------------------------------------------------------------------------------- Variable MICS-CABG\ Conventional\ Statistical Test Statistic p-value Significant? Mean (SD)\ Mean (SD)\ Test Median Median ----------------- ------------- --------------- -------------- --------------- --------- -------------- Creatinine 24h 1.12 (0.28)\ 1.38 (0.42)\ Mann-Whitney U U=1611.0 \< 0.001 YES (mg/dL) Median=1.08 Median=1.35 Creatinine 48h 1.26 (0.58)\ 1.92 (1.15)\ Mann-Whitney U U=1452.5 \< 0.001 YES (mg/dL) Median=1.14 Median=1.56 Creatinine 72h 1.21 (0.56)\ 1.83 (1.07)\ Mann-Whitney U U=1472.0 \< 0.001 YES (mg/dL) Median=1.10 Median=1.56 eGFR 48h 67.67 48.59 (24.14)\ Indep. t-test t(148)=4.988 \< 0.001 YES (mL/min/1.73m²) (22.68)\ Median=46.9 Median=67.0 Urea 48h (mg/dL) 43.25 49.43 (16.51)\ Indep. t-test t(148)=−2.493 0.014 YES (13.72)\ Median=49.9 Median=41.7 BUN 48h (mg/dL) 20.21 (6.41)\ 23.10 (7.72)\ Indep. t-test t(148)=−2.493 0.014 YES Median=19.5 Median=23.3 Creatinine Change 0.26 (0.52) 0.76 (1.02) Mann-Whitney U U=1570.0 \< 0.001 YES Δ48h Creatinine Ratio 1.28 (0.55) 1.69 (1.03) Mann-Whitney U U=1786.0 \< 0.001 YES 48h ------------------------------------------------------------------------------------------------------- **Note:** All comparisons statistically significant (p ≤ 0.014). Mann-Whitney U used for non-normally distributed variables (Creatinine 24/48/72h, ΔCreatinine, Creatinine Ratio). Independent t-test used for BUN, Urea, eGFR 48h (normally distributed in both groups). MICS-CABG consistently showed lower creatinine and higher eGFR across all time points. **Serial Postoperative Serum Creatinine** In the category of median sternotomy, the serum creatinine levels were also significantly raised at 24, 48 and 72 hours after surgery. At 24 hours as shown early in table 5.16, mean serum creatinine was 1.38 +/- 0.42 mg/dL in the Conventional group as compared in the Minimally Invasive category mean serum creatinine was 1.12 +/- 0.28 mg/dL, the differentiation between these two categories were statistically significant (Mann-Whitney U test, U = 1611.0, p \< 0.001).At 48 hours, the difference of creatinine levels extended ahead, the category of Conventional noted of 1.92 +/- 1.15 mg/dL compared to 1.26 +/- 0.58 mg/dL in the Minimally Invasive group (Mann-Whitney U, U = 1452.5, p \< 0.001). At 72 hours, in the Conventional surgery category the values of serum creatinine levels remained significantly elevated at 1.83 +/- 1.07 mg/dL versus 1.21 +/- 0.56 mg/dL (Mann-Whitney U, U = 1472.0, p \< 0.001). The creatinine change at 48 hours (delta creatinine) was 0.76 +/- 1.02 mg/dL in the Conventional group while in the Minimally Invasive category 0.26 +/- 0.52 mg/dL (Mann-Whitney U, U = 1570.0, p \< 0.001), and the creatinine ratio at 48 hours was 1.69 +/- 1.03 in median sternotomy versus 1.28 +/- 0.55 in micscabg (Mann-Whitney U, U = 1786.0, p \< 0.001). ![](media/image26.png){width="4.196332020997375in" height="2.5998075240594924in"} []{#_Toc230618454 .anchor}**Figure 5. 24 Serial serum creatinine trend from baseline through 72 hours postoperatively** **Note.** The chart (mean +/- SD) showing serum creatinine at baseline 24h, 48h, and 72h after surgey for the Minimally Invasive and Conventional category. Dashed horizontal line represents the upper normal limit (1.2 mg/dL). Significance annotations shown at each postoperative time point. **Postoperative Estimated Glomerular Filtration Rate** At 48 hours, the The traditional median sternotomy category had a considerably lower eGFR (48.59 +/- 24.14 mL/min/1.73m2) than the Minimally Invasive category (67.67 +/- 22.68 mL/min/1.73m2; t(148) = 4.988, p \<.001). Both categories\' eGFR dropped during the baseline and 48 hours, as shown in Figure 5.25, although the Conventional category\'s decline was considerably higher. At 48 hours, eGFR was within 60 mL/min/1.73 m2 in 74.7% of Conventional patients and 40.0% in the Minimally Invasive group (chi2(2) = 18.556, p \<.001). 60% of the Minimal In contrast to 25.3% of conventional patients, minimally invasive patients achieved normal or nearly normal eGFR (\>= 60 mL/min/1.73m2). ![](media/image27.png){width="4.2842814960629925in" height="3.2875306211723534in"} []{#_Toc230618455 .anchor}**Figure 5. 25eGFR trend from baseline to 48 hours postoperatively by surgical approach**. **Note:**eGFR for the Minimally Invasive and Conventional categories at startng point and 48 hours after surgery is representing in above error bar chart (mean +/- SD). The CKD threshold (60 mL/min/1.73m2) is presented by the orange dashed line. At 48 hours, t(148) = 4.988, p \<.001. **Postoperative Serum Urea and Blood Urea Nitrogen** In the category of median sternotomySerum urea at 48 hours was significantly elevated (49.43 +/- 16.51 mg/dL) in contrast to the category of Minimally Invasive (43.25 +/- 13.72 mg/dL; t(148) = -2.493, p = .014), as shown in Figure 5.26. Blood urea nitrogen (BUN) at 48 hours displaying same pattern, with elevated values in the Conventional category (23.10 +/- 7.72 mg/dL) as compared to the Minimally Invasive group (20.21 +/- 6.41 mg/dL; t(148) = -2.493, p = .014). The chi-square analysis of the categorical BUN distribution showed that distribution of BUN under 24 mg/dL was higher in Minimally Invasive (74.7%) than in Conventional (53.3%) (chi2(2) = 7.912, p = .019). In the urea ranges, 73.3% of Minimally Invasive participants represented with urea values between 40 and 50 mg/dLin contrast with the Conventional group, 50.7% had values in this range (chi2(2) = 8.186, p = .017); while 13.3% of Minimally Invasive patients had a urea \> 60 mg/dL, 25.3% of Conventional participants with level of urea \> 60 mg/dL. ![](media/image28.png){width="4.292115048118985in" height="3.317030839895013in"} []{#_Toc230618456 .anchor}**Figure 5. 26 Serum urea at 48 hours postoperatively by surgical approach.** **Note.** Bar chart displaying mean serum urea with standard deviation error bars for the Minimally Invasive and Conventional groups. t(148) = -2.493, p = .014. **Summary of Key Renal Parameters at 48 Hours** The three main renal parameters at 48 hours are shown in Figure 5.27 as box plots with individual data point overlays representing serum urea, eGFR, and creatinine. The distributions analyzed support the above-mentioned model, showing that the Conventional category had greater urea rates (p =.014), lower eGFR readings (p \<.001), and higher creatinine amounts (p \<.001) than the Minimally Invasive category. In line with a wider spectrum of AKI degree of severity, the Conventional category also showed more fluctuation in creatinine readings. ![](media/image29.png){width="6.0in" height="2.253731408573928in"} []{#_Toc230618457 .anchor}**Figure 5. 27 Distribution of serum creatinine, eGFR, and serum urea at 48 hours by surgical approach.** **Note.** Box plots with individual data point overlays. Left sided panel presents: serum creatinine (p \< .001). Middle ones panel shows: eGFR in mL/min/1.73m2 (p \< .001). Right sided panel indicate: serum urea in mg/dL (p = .014). Individual data points shown as semi-transparent dots. **Creatinine Change and Ratio at 48 Hours** The absolute 48-hour creatinine change and creatinine ratio distribution are shown in Figure 5.28. The distribution of creatinine variation (delta 0.76 +/- 1.02 mg/dL vs. 0.26 +/- 0.52 mg/dL; p \<.001) and the creatinine levels (1.69 +/- 1.03 vs. 1.28 +/- 0.55; p =.002) was significantly more extensive and greater in the Conventional group of participants. According to KDIGO recommendations, an adjustment of ≥ 0.3 mg/dL along with a ratio of ≥ 1.5 are regarded as thresholds for establishing AKI (the dotted red lines in Figure 5,28).A significantly higher percentage of the Conventional patients were above these thresholds, as compared to the Minimally Invasive patients. ![](media/image30.png){width="6.0in" height="2.835820209973753in"} []{#_Toc230618458 .anchor}**Figure 5. 28 Distribution of creatinine change and creatinine ratio at 48 hours by surgical approach**. **Note.** Violin plots with embedded box plots. Left panel: absolute creatinine change (delta, mg/dL) with KDIGO threshold at 0.3 mg/dL (red dashed line). Right panel: creatinine ratio at 48h with KDIGO threshold at 1.5x (red dashed line). t-test p values displayed per panel. **Primary Outcome: Incidence of Acute Kidney Injury** The main outcome of this study was the incidence of early acute kidney injury (AKI) (within 48--72 hours after surgery) by KDIGO 2012 criteria. 46 (30.7%) of 150 patients developed early postoperative AKI. See Table 5.17 and Figure 5.29 for different incidences of AKI in the two surgical groups. Of the patients in the Minimally Invasive group, 10 (13.3%) developed early AKI. Of the Conventional group, 36 (48.0%) developed early AKIThe distinction was significant in statistical terms, according to a chi-square test analysis (chi2(1) = 19.597, p \<.001). The other assumption claiming there is a substantial difference in the frequency of early AKI comparing the two surgical techniques is supported since this was 3.6 times higher in the Conventional group and the null hypothesis was not accepted. []{#_Toc230618427 .anchor}**Table 5. 17: Comparison of AKI Incidence Between Surgical Groups** --------------------------------------------------------------------------------- Group AKI Yes n AKI No n Chi-square df p-value Significant? (%) (%) -------------- --------- --------- ------------ -------- --------- -------------- MICS-CABG 10 65 19.597 1 \< 0.001 YES (n=75) (13.3%) (86.7%) Conventional 36 39 (n=75) (48.0%) (52.0%) Total (n=150) 46 104 (30.7%) (69.3%) --------------------------------------------------------------------------------- **Note:** AKI = acute kidney injury. AKI diagnosed per KDIGO instructions: elevation of serum creatinine \>= 0.3 mg/dL within 48 hours, or \>= 1.5 times baseline, or urine output \< 0.5 mL/kg/hr for \>= 6 hours. p\< .05 considered statistically significant. ![](media/image31.png){width="4.5in" height="2.309757217847769in"} []{#_Toc230618459 .anchor}**Figure 5. 29: Comparison of Early AKI Incidence Between Surgical Groups (N=150).** **Note:** The prevalence of AKI was 13.3% in the MICS-CABG group of participants and 48.0% in the Conventional group of participants, according to the bar graph. The difference is statistically significant (p \< 0.001, Chi-square = 19.597). **AKI Stage Distribution (KDIGO Criteria)** In the patients with AKI, there was also a significant difference in stage distribution between the groups (chi2(3) = 21.533, p \< .001) as shown in Table 5.18 . In Minimally Invasive category of patients there were 7 patients (9.3%) suffering from Stage 1, only 1 patient (1.3%) had Stage 2 and 2 patients (2.7%) had Stage 3 AKI. On the other hand, the Conventional category of surgery there were 23 patients (30.7%) experiencing with stage 1, 7 patients (9.3%) had stage 2, and 6 patients (8.0%) had stage 3 AKI respectively. The percentage of patients with combined severe AKI (Stages 2 and 3) was 18.3% for the median sternotomyparticipanatsand 4.0% for the Minimally Invasive category participants. []{#_Toc230618428 .anchor}**Table 5. 18: AKI Stage Distribution by Surgical Group** ----------------------------------------------------------------------------------- AKI MICS-CABG n Conventional n Total n Chi-square p-value Significant? Stage (%) (%) (%) -------- ----------- -------------- --------- ------------ --------- -------------- No AKI 65 (86.7%) 39 (52.0%) 104 21.533 \< 0.001 YES (69.3%) Stage 1 7 (9.3%) 23 (30.7%) 30 YES (20.0%) Stage 2 1 (1.3%) 7 (9.3%) 8 (5.3%) YES Stage 3 2 (2.7%) 6 (8.0%) 8 (5.3%) YES ----------------------------------------------------------------------------------- **Note:** Chi-square = 21.533, p \< 0.001. Stage 1 was the most common AKI stage in both groups. Severe AKI (Stage 2 and 3) was present in 17.3% of Conventional and 4.0% of MICS-CABG participants. ![](media/image32.png){width="4.5in" height="2.7796905074365705in"} []{#_Toc230618460 .anchor}**Figure 5. 30 *AKI Stage Distribution Between Surgical Groups (N=150).*** **Note:** Conventional group had higher proportions of all AKI stages: Stage 1=30.7%, Stage 2=9.3%, Stage 3=8.0% vs MICS-CABG: Stage 1=9.3%, Stage 2=1.3%, Stage 3=2.7%. **Comparison of Categorical Renal Parameters at 48 Hours** Renal function parameters at 48 hours were further classified into clinically defined categories and compared between groups using Chi-square tests (Table 5.1). []{#_Toc230618429 .anchor}**Table 5. 19: Comparison of Categorical Renal Parameters at 48 Hours** ----------------------------------------------------------------------------------- Variable MICS-CABG n Conventional n Chi-square df p-value Significant? (%) (%) ---------- ----------- -------------- ------------ ------- --------- -------------- BUN \< 24 56 (74.7%) 40 (53.3%) 7.912 2 0.019 YES mg/dL (normal) BUN 24--40 19 (25.3%) 34 (45.3%) 0.019 YES mg/dL BUN \> 40 0 (0.0%) 1 (1.3%) 0.019 YES mg/dL Urea 55 (73.3%) 38 (50.7%) 8.186 2 0.017 YES 40--50 mg/dL Urea 10 (13.3%) 18 (24.0%) 0.017 YES 50--60 mg/dL Urea \> 60 10 (13.3%) 19 (25.3%) 0.017 YES mg/dL eGFR ≥90 0 (0.0%) 0 (0.0%) 18.556 2 \< 0.001 YES mL/min eGFR 33 (44.0%) 13 (17.3%) \< 0.001 YES 60--89 mL/min eGFR\< 60 30 (40.0%) 56 (74.7%) \< 0.001 YES mL/min Low Urine 12 (16.0%) 18 (24.0%) 1.042 1 0.307 No Output: Yes Low Urine 63 (84.0%) 57 (76.0%) 0.307 No Output: No ----------------------------------------------------------------------------------- **Note:** Significant category variations were found for BUN (p=0.019), Urea (p=0.017), and eGFR (p\<0.001) categories. Low urine output showed no significant difference between both surgical groups (p=0.307). **Risk Factors Associated with Acute Kidney Injury** Chi-square testing and odds ratios estimations were used to analyze hypothetical clinical determinants in order to find individual risk variables for AKI.. Table 5.20 presents the results for all evaluated risk factors. []{#_Toc230618430 .anchor}**Table 5. 20: Risk Factors Associated with AKI Development --- Odds Ratio Analysis** ---------------------------------------------------------------------------------- Risk Factor AKI Yes n AKI No n Odds Chi-square p-value Significant? (%) (%) Ratio -------------- --------- ---------- -------- ------------ --------- -------------- Low Urine 22 8 (7.7%) 11.0 29.648 \< 0.001 YES Output (47.8%) Conventional 36 39 (37.5%) 5.88 19.597 \< 0.001 YES Surgery (78.3%) Diabetes 14 29 (27.9%) 1.13 0.015 0.902 No Mellitus (30.4%) Hypertension 44 104 0.0 1.874 0.171 No (95.7%) (100.0%) Chronic Kidney 4 (8.7%) 10 (9.6%) 0.90 0.0 1.000 No Disease Smoking 14 26 (25.0%) 1.31 0.244 0.621 No (30.4%) Male Gender 40 93 (89.4%) 0.79 0.026 0.873 No (87.0%) ---------------------------------------------------------------------------------- **Note:** Only two factors were statistically significant, one is low urine output (OR=11.0, p\<0.001) and the other is conventional surgical approach (OR=5.88, p\<0.001). Traditional comorbidities including diabetes, hypertension, CKD, smoking, and male gender were not independent predictors of AKI in this table. ![](media/image33.png){width="4.106656824146982in" height="2.6165266841644796in"} []{#_Toc230618461 .anchor}**Figure 5. 31Prevalence of risk factors in patients with and without early AKI.** **Note.** The percentage that consists of participants with all of the risk factors with or without AKI Yes (n = 46) and AKI No (n = 104) categories is shown in a grouping bar chart. The entire set of bars is accompanied with statistical significance labels (p values and significance markers). # CHAPTER 6 {#chapter-6 .unnumbered} # DISCUSSION {#discussion .unnumbered} The aim of this study was to determine the incidence of early acute kidney injury (AKI) within 48 to 72 hours after on-pump coronary artery bypass grafting (CABG) using minimally invasive anterior mini thoracotomy versus conventional median sternotomy. The results are presented with respect to the study hypotheses, specific objectives and literature review below. The null hypothesis (H0) was that the frequencies of early AKI would be the same in patients undergoing on-pump CABG performed via minimally invasive sternotomy compared with conventional sternotomy. The alternative hypothesis (H1) was that there is a significant difference. The results of this study provide strong statistical evidence to reject the null hypothesis. There was a 3.6-fold difference in the incidence of early AKI -- 13.3% in the Minimally Invasive group and 48.0% in the Conventional group (chi2(1) = 19.597, p \< .001). These data support acceptance of the alternative hypothesis. The results corroborate the overall concept that surgical technique plays a meaningful role on postoperative organ function, especially during the early postoperative and perioperative period when the haemodynamic, inflammatory and ischemic insults are the most intense (Kamla et al., 2025) The primary aim was to identify and compare the severity of early AKI in minimally invasive CABG patients (mini thoracotomy) with full median sternotomy (conventional) CABG patients. The total incidence of AKI found in this study (30.7%) is similar to published figures. The incidence of AKI after CABG has been reported to be between 4% and more than 30%, depending on the criteria used and the characteristics of the population studied (Zeyneloglu et al., 2011). Higher rates are often found when more sensitive diagnostic tools are used, like in the present study (KDIGO 2012 criteria). The KDIGO classification system is sensitive: Schiefer. et al. (2023) reported that 57.3% of the patients in an ICU and 44.3% of patients in the postoperative setting had developed AKI per KDIGO criteria in a large global patient cohort. The incidence of AKI (48.0%) in the Conventional group is in line with previous studies of conventional sternotomy CABG. In a recent retrospective study, Hiew et al. (2016) found an overall incidence rate of 36.2% for AKI in 1260 patients who underwent CABG surgery. Vives et al. (2019) also reported various risk factors for AKI after cardiac surgery, with the severity of surgical trauma and hemodynamic perturbation being key factors. The significantly reduced incidence of AKI in the Minimally Invasive group (13.3%) is consistent with the biological benefits of less invasive procedures. In their study comparing MICS-CABG with conventional CABG, Sljivo et al. (2025) found that there was significantly decreased blood loss, shorter ventilation, and higher rates of less transfusions in the minimally invasive group and each of these factors was independently associated with a reduction of renal stress. This is further reflected in the stage distribution of AKI. The incidence of Combined AKI (Stage 2 and 3) was 18.3% in Conventional patients compared to 4.0% in Minimally Invasive patients. The relevance of this clinical distinction is that there is a 3-8 fold increase in perioperative mortality rates and an increase in length of stay in the ICU and hospital among patients with severe AKI (Yu et al., 2023). In the study by Thakar et al. (2005), it was found that even small increases in post-operative creatinine were an independent predictor of in-hospital death and longer hospital stay following open-heart surgery. This Conventional group severe AKI concentration thus has implications for patient outcomes as well as healthcare resource utilisation. This current study differed from Sellin et al. (2024), the parent study on which this was based, who found no difference in renal parameters after surgery between the minimally invasive (TCRAT) and conventional sternotomy groups, and the same ARF rates of 28.8% in each. But there are some important methodological discrepancies that explain this divergence. In contrast to Sellin et al. this study was retrospective, measurements were made at hospital discharge, not within 48 hours, and ARF was defined by AKIN. The present study is prospective, multi-centred, uses the more sensitive KDIGO 2012 criteria and specifically focuses on the earliest 48-hour period, when the acute haemodynamic and inflammatory insults are most marked. All these differences in design are in line with the concept of Schopka et al. (2014) that the criteria and the timing of the assessment of AKI are important determinants of the incidence rate reported. The second aim was to assess the serum creatinine, eGFR, urea and blood urea nitrogen level changes between the two surgical groups at 48 hours. Serial creatinine was significantly increased in Conventional group at all three postoperative timepoints (24h, 48h, 72h; all p \< .001). The trajectory seen in the Conventional group - peaking at 48 hours and partially recovering at 72 hours represents the typical course of cardiac surgery associated with AKI (CSA-AKI). Kamla et al. (2025) explained this common scenario of ATI reaching its peak 24 to 48 hours after surgery, and reported that failure to recover completely by 72 hours after surgery is a predictor of chronic kidney disease.(Kamla et al., 2025) As indicated by Brown et al. (2006), the subjects who were diagnosed with an increase in creatinine level more than 50 percent above their baseline level exhibited higher mortality rate within 90 days in a research conducted on about 1,391 CABG subjects. While the creatinine ratio (Crt) for the Conventional group was 1.69 at 48 hours, it was 1.28 for the Minimally Invasive group. A greater proportion of patients in the Conventional group attained or came close to a clinically meaningful Crt. Additionally, the Conventional group\'s delta creatinine after 48 hours was 0.76 +/- 1.02 mg/dL, while the Minimally Invasive group\'s was 0.26 +/- 0.52 mg/dL, indicating a more severe and acute renal insult after sternotomy(Brown et al., 2006). The eGFR at 48 hours was significantly decrease in the Conventional category (48.59 +/- 24.14 mL/min/1.73m2 vs. 67.67 +/- 22.68 mL/min/1.73m2; p \< .001). In particular, 74.7% of Conventional patients, but 40.0% of Minimally Invasive patients had contraindications for the CKD-level of 60 mL/min/1.73m2 at 48 hours. Preoperative eGFR\< 60 mL/min was found to be the strongest single predictor of postoperative AKI (Vives et al., 2019)the present data add to this finding by showing that, independent of the preoperative eGFR, the surgical approach itself is a strong predictor of the extent of the eGFR decline in the early postoperative period. The Conventional group had significantly higher levels of serum urea and BUN at 48 hours (p = .014 for both). Both higher levels of urea and BUN are indicative of higher protein turn-over and lower renal clearance, which is typical of the catabolic and inflammatory response to higher surgical trauma (Dimopoulos et al., 2023). The high tissue exposure from conventional sternotomy should exacerbate these effects, as the pattern of nitrogenous retention described by Kant et al. (2023) included CPB-induced haemolysis and vascular dysfunction. To objective quantify the differences between groups in early renal stress, the categorical analysis of urea and BUN distributions was done and revealed that larger proportions of Conventional patients reported higher category values compared to Leaky patients. Several pathophysiological mechanisms interact to account for the observed difference in the frequency of AKI in the two groups. The AKI that occurs after heart surgery is the result of several perioperative mechanisms that represent complex haemodynamic and inflammatory insults (Dimopoulos et al., 2023). Conventional median sternotomy is associated with a larger incision, periosteal trauma, a greater amount of pericardial manipulation and a higher degree of systemic inflammatory activation than minimally invasive anterior mini thoracotomy. This systemic inflammatory response to surgical insult includes pro-inflammatory cytokines, complement, and neutrophils, all of which lead to endothelial damage, renal vasoconstriction, and tubular cell death. This process is worsened by the use of cardiopulmonary bypass, which causes hemolysis and dysfunction of blood vessels, both of which are associated with renal damage after surgery (Kant et al., 2023). A second major mechanism is renal hypo perfusion. Non-pulsatile flow during CPB, intraoperative hypotension and anaesthetic-induced vasodilatation cause decreased renal oxygen delivery and lead to ischaemia-reperfusion injury. Factors that exacerbate poor renal perfusion and thus contribute to the risk of AKI include nephrotoxic substances, intraoperative hypotension, hypoperfusion, and oxidative stress (Dimopoulos et al., 2023).Conventional sternotomy is expected to cause more pre- and intra-operative blood loss, fluid shifts and haemodynamic instability, which would lead to a more prolonged and severe renal hypoperfusion than the minimally invasive procedure. This is a direct clinical correlate of the finding in the present study that low urine output was an odds ratio of 11.0 for the development of AKI. Oliguria is a sign and early warning signal of reduced renal perfusion, and it is a manifestation and early warning signal of impending tubular injury (Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group, 2012).. The level of surgical trauma is a partial explanation for why the inflammatory and hemodynamic insults of CPB vary in magnitude, as CPB was used in both groups. According to Vives et al. (2019) CPB time and aortic cross-clamp time are risk factors for AKI, particularly if associated with complications and bleeding. Minimally invasive techniques that minimize the opening of the chest and disruption of tissues help reduce this amplifying effect of surgical trauma on renal injury caused by CPB. In this study, only low urine output was statistically significant as a risk factor for AKI (OR = 11.0, p \< .001). This is in line with the known pathophysiology of CSA-AKI, in which renal perfusion deficits play a key role (Vives et al., 2019). Several factors are known to influence the autoregulatory ability of the kidneys and make them more susceptible to AKI, such as the pre-existing conditions of diabetes, renal disease and hypertension, but these variables were not significant in the current study. The most plausible explanation is that with the 150 patient sample size, the statistical power is inadequate to detect small associations, especially as the prevalence of hypertension was very high (98.7%) and there was little statistical variation for this variable to differentiate between groups. Hiew et al. (2016) found insulin-dependent diabetes, raised preoperative creatinine and CPB time to be independent risk factors for AKI in a large Southeast Asian cohort of 1,260 CABG patients. Vives et al. (2019) added that pre-op eGFR\< 60 mL/min was the most powerful pre-op predictor of post-op AKI. In the current study, both groups were \> 60 mL/min at baseline and the dialysis-dependent renal failure patients were excluded by design, resulting in the potential loss of discriminatory power of CKD as a risk factor. These earlier studies would be likely duplicated in larger studies with more variable baseline renal function. It is also noteworthy that there was no significant association between male gender and AKI in the present study. The limitation of the present cohort is that only 11.3% of our subjects were females, thus reducing the statistical power to determine a gender-related effect as Vives et al. (2019) reported. Thus, the present results should be viewed within the limits of the sample size and in the final study multivariate regression analysis should be undertaken, allowing the adjustment for confounding variables. The results of this study are directly applicable in the clinical management of patients with salivary stones and in decision-making for their surgical treatment. Acute kidney injury following CABG has been associated with a number of negative outcomes including a significant risk of future development of progressive renal disease, longer hospital stays, increased hospital costs and increased mortality and morbidity (Reents et al., 2014).Previous studies and the present one suggest that in appropriately selected surgical candidates, choosing the minimally invasive approach may significantly decrease the burden of early postoperative renal injury as the frequency of occurrence of early AKI in the Conventional group was 3.6-fold higher. Small rises in serum creatinine levels after surgery have been reported to be independently associated with longer hospital stays, higher medical costs and greater mortality (O'Neal et al., 2016). Prevention of eGFR\> 90% decrease (Stage 1 AKI) therefore has clinical and economic value. Sef et al. (2024) conducted a systematic review of 26 studies involving 7,556 patients and found that minimally invasive techniques had positive procedural safety and early recovery profiles. The present study adds to this evidence base by directly showing a renal advantage of the minimally invasive approach in the local population of cardiac surgical patients in Pakistan, for whom there were no data (Sef et al., 2024).Guangxin et al. (2024) were found that patients with Type 2 diabetes and CAD had same progessof revascularization of MICS-CABG and conventional CABG without providing any AKI data (Guangxin et al., 2024).By establishing that such a renal benefit is also present in this patient population, the current study closes this gap. Furthermore, poor urine production results in a Likelihood from 11.0 for AKI, emphasizing that, no matter the surgical technique, immediate intervention in individuals with oliguria and thorough monitoring of urine production during surgery should serve as a therapeutic priority. **\ ** # CHAPTER 7 {#chapter-7 .unnumbered} ## Conclusions The current study also demonstrates that patients undergoing CABG with the use of the cardiopulmonary bypass in which the incidence of AKI within 48 to 72 hours after the surgical procedure was significantly lower among patients in the Minimally Invasive group (13.3%) than among patients in the Conventional group (48.0%, chi2(1)=19.597, p\<.001). Significant differences in all the post-operative parameters concerning renal function were seen in Conventional patients and the other group patients including serum creatinine levels at 24, 48 and 72 hours, GFR, urea and BUN levels at 48 hours. The percentage of Minimally Invasive patients developing severe AKI (Stages 2 and 3 together) was significantly smaller (only 4.0% of patients) than that among patients in the Conventional group (18.3%). However, the only significant risk factor associated with AKI was a lower urine output (OR=11.0, p\<.001). Such results complement the accumulating evidence that minimally invasive cardiac surgical procedures are beneficial not only in terms of wound healing and recovery but with regard to the preservation of early postoperative renal function as well. Since a small postoperative rise of creatinine is an independent risk factor for mortality and health care expenses (O'Neal et al., 2016), surgical approach may be a modifiable determinant of renal outcomes in CABG patients. This study adds basic information from the Pakistani cardiac surgical environment and supports conducting large, multicentre prospective trials to validate these findings and inform evidence-based surgical decision making. **\ ** ## Recommendations From the above results, minimally invasive anterior minithoracotomy CABG is superior compared to conventional median sternotomy CABG since this surgical procedure had low probability of causing postoperative acute kidney injury. In order to minimize blood transfusions and shorten the length of cardiopulmonary bypass, aortic cross clamping, and blood loss, preoperative precautions should be taken into consideration. Within 48 to 72 hours following cardiac surgery, it is critical to thoroughly evaluate the patient\'s blood tests, including serum creatinine, estimated glomerular filtration rate, blood urea nitrogen, serum urea, and urine volume, in order to detect renal issues that may arise. Patients with reduced urine production should have their kidney function closely monitored since they are more vulnerable to renal issues following surgery.. Finally, centers performing cardiac surgeries are advised to adopt renal protection strategies and minimally invasive procedures in their work practices. Studies conducted at several centers and involving large patient groups are required to verify the findings obtained in this study and evaluate the use of other potential biomarkers such as NGAL, KIM-1, cystatin-C, and neprilysin. **\ ** ## Limitations There are a number of limitations to this study that must be recognized. First, the sample of 150 patients is sufficient for the primary chi-squared comparison but offers a relatively low statistical power to assess for modest association of individual risk factors with AKI outcomes. Second, intraoperative variables like CPB time, aortic cross-clamp time, intraoperative blood pressure, vasopressor use, and intraoperative blood transfusion volumes, which are all known to contribute to CSA-AKI (Vives et al., 2019), were not included in the study. Third, follow-up of the kidneys was limited to 72 hours only and this prevented the evaluation of recovery trends of AKI, progression to chronic kidney disease or long-term survival. Fourth, preoperative baseline creatinine and eGFR did differ significantly between the two groups, although this difference was small, it may be a potential confounder. It is recommended to perform multivariable regression analysis to adjust for the baseline effect of renal function to confirm the independence of surgical approach effect. This has been highlighted by Slaughter et al. (2025) to ensure that any differences in outcomes seen in comparative cardiac surgery studies are due to the surgical technique and not to the differences in the patients\' preop characteristics(Slaughter et al., 2025). **\ ** # CHAPTER 8 {#chapter-8 .unnumbered} # REFERENCES {#references .unnumbered} Abdullah, H. A., Saeed, D. N., Flaih, A. H., & Barzani, M. A. (2025). Impact of surgical urgency on outcomes after minimally invasive coronary artery bypass surgery: a retrospective cohort study. *J Cardiothorac Surg*, *21*(1), 43. Baishya, J., George, A., Krishnamoorthy, J., Muniraju, G., & Chakravarthy, M. (2017). Minimally invasive compared to conventional approach for coronary artery bypass grafting improves outcome. *Ann Card Anaesth*, *20*(1), 57-60. Bernardi, M. H., Wagner, L., Ryz, S., Puchinger, J., Nixdorf, L., Edlinger-Stanger, M., Geilen, J., Kainz, M., Hiesmayr, M. J., & Lassnigg, A. (2021). 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Acute kidney injury after coronary artery bypass grafting surgery. *Critical care*, *15*(1), P101. **\ ** # CHAPTER 9 {#chapter-9 .unnumbered} # ANNEXURES {#annexures .unnumbered} ## ADD THE TABLES AND FIGURES ACCORDING TO THE DEPARTMENTAL REQUIRMENT ## CONSENT FORMS **CONSENT FORM IN ENGLISH** **Description of the Research and Your Participation** **You are invited to participate in a research study conducted by\_\_\_\_\_\_\_\_\_\_\_\_\_\_.** **The purpose of this research is to evaluate the "\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_".** **Risks and Discomforts** Mention if there will be any known risks associated with this research. **Potential Benefits** Mention if there will be benefits to the participant that would result from their participation in this research. **Protection of Confidentiality** We will do everything we can to protect your privacy. Your identity will not be revealed in any publication resulting from this study. **Voluntary Participation** Your participation in this research study is voluntary. You may choose not to participate and you may withdraw your consent to participate any time. You will not be penalized in any way should you decide not you participate or to withdraw from this study. **CONSENT** **I have read this consent form and have been given the opportunity to ask questions. I give my consent to participate in this study.** Participant's Signature \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Date: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ A copy of this consent form should be given to the participant. [تحقیقمیں شرکت کا دعوت نامہشمولیت کی دعوت دیتا /دیتی ہوں]{dir="rtl"} [عنوان]{dir="rtl"}: [نقصانات اور تکلیف: اس تحقیق سے کسی قسم کے نقصان یا تکلیف کا اندیشہ نہیں ہے ۔]{dir="rtl"} [ممکنہ فوائد: آپکو ایک اہم تحقیق میں حصہ لینے کا موقعہ دیا جاۓ گا۔]{dir="rtl"} [رازداری کا تحفظ: ہم آپ کی معلومات کے تحفظ کے لیے وہ سب کچہ کریں گے جو ہم کر سکتے ہیں۔ تحقیق کے متعلق اکٹہی کیی گيی تمام معلومات کو انتہا ئی خفیہ رکھا جاے گا۔ ڈیٹا انٹری اور تجزیے کے دوران آپ کے متعلق وہ تمام معلومات جن سے آپ کی شناخت ہو سکتی ہو کو ختم کر دیا جاے گا۔ اس تحقیق کے نتیجے میں شائع ہونے والی کسی بھی اشاعت میں آپ کی شناخت کو ظاہر نہیں کیا جاے گا۔]{dir="rtl"} [رضاکارانہ شمولیت: اس تحقیقی مطالعہ میں آپ کی شرکت رضاکارانہ ہے۔ آپ کو شرکت نہ کرنے اور کسی بھی وقت پغیر وجہ بتانے اس تحقیق میں شمولیت کو چھوڑنے کا اختیار ہے۔ شرکت نہ کرنے یا اس میں شمولیت کو چھوڑنے کی صورت میں آپ کے خلاف کوئی کاروايی نہیں کی جاے گی]{dir="rtl"} [درجذیل معلومات تحقیق میں شامل ہونے والوں کے لیے پڑھیں اور ان کا جواب دیے گیے خانوں میں درج کریں۔]{dir="rtl"} - [میں نے معلوماتی شیٹ جو کہ تحقیق کی وضاحت کر رہی ہے کو سمجھ لیا ہےاورمجھے تحققیق کے سوالات کرنے کا موقع دیا گیا تھا۔]{dir="rtl"} - [میں سمجھ گیا/گيی ہوں کہ میری شرکت رضاکارانہ ہے اور یہ کہ میں کسی بھی وقت اپنا ارادہ بدل سکتا/سکتی ہوں اور تحقیق سے دستبردار ہو سکتا/سکتی]{dir="rtl"} - [میں سمجھ گیا/گیی ہوں کہ میرے جوابات خفیہ رکھے جاءیں کے۔ میں محقیقیين کو اس بات کی اجازت دیتا/دیتی ہوں کے وہ جوابات کو جانچ سکیں۔]{dir="rtl"} - [میں سممجھ گیا/گی ہوں کے معلومات میرے نام کے بجاے نمبر کی صورت میں محفوط کی جائيں گی۔ تا کہ میں نتائج کی اشاعت کے دوران کسی بھی طرح سے شناخت نہ کیا جا سکوں۔ میں اس بات سے رضامند ہوں کے جو معلومات مجھ سے لی جائہيں گی وہ تحقیق میں استعمال ہوں گی۔]{dir="rtl"} - [میں اوپر بتایی گی تحقیق میں شامل ہونے کے لیے رضامند ہوں اور محقیقین کو اپنا پتہ تبدیل ہونے کی صورت میں مطلع کروں گا/گی۔]{dir="rtl"} > [رضا مندی:ميں نے يہ اجازت نامہ پڑھا ہے اور مجھے سوال پوچھنے کا موقع > ديا گيا ہے۔ ميں اس سٹڈی ميں شرکت کے راضی ہوں**۔**]{dir="rtl"} [شرکت کنندہ کا نام \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ دستخط\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ تاريخ]{dir="rtl"} **\_\_\_\_\_\_\_\_\_\_\_** [اجازت لينے والے کا نام \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ دستخط \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_تاریخ]{dir="rtl"} **\_\_\_\_\_\_\_\_\_\_\_\_** [اس اجازت نامہ کی ايک نقل آپکو دی جانی چاہے**۔ **]{dir="rtl"} ## PROFORMA/QUESTIONNAIRE **Frequency of Early Acute Kidney Injury After On-Pump CABG: A Comparison Between Minimally Invasive and Conventional Sternotomy** **Section A: Demographic Data** 1. Patient ID: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 2. Age Range:\ ☐20--30years\ ☐31--50years\ ☐\>50 years 3. Gender: ☐ Male ☐ Female 4. BMI Category:\ ☐**Underweight** (\<18.5 kg/m²)\ ☐**Normal weight** (18.5--24.9 kg/m²)\ ☐**Overweight** (25--29.9 kg/m²)\ ☐**Obese** (≥30 kg/m²) > **Section B: Preoperative Clinical Data** 5. Diabetes Mellitus: ☐ Yes ☐ No 6. Hypertension: ☐ Yes ☐ No 7. Chronic Kidney Disease: ☐ Yes ☐ No 8. Smoking Status: ☐ Yes ☐ No 9. Baseline Serum Creatinine (mg/dL): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 10. Estimated GFR (mL/min/1.73m²): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 11. Left Ventricular Ejection Fraction (%): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ ☐ ≥55% ☐ 41%-54% ☐\<40% 12. Preoperative Hemoglobin (g/dL): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Section C: Surgical Records** 13. Surgical Approach: ☐ Minimally Invasive Anterior Mini thoracotomy ☐ Conventional Median Sternotomy **Section D: Postoperative Renal Assessment (Within 48--72 Hours)** 14. Serum Creatinine at 24 hours (mg/dL): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 15. Serum Creatinine at 48 hours (mg/dL): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 16. Serum Creatinine at 72 hours (mg/dL): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 17. Urine Output \<0.5 mL/kg/hr for ≥6 hours: ☐ Yes ☐ No 18. Serum creatinine(mg\\dl): - \<0.3 - 2.0-2.9 - \>3 19. Blood Urea Nitrogen (BUN, mg/dl): - \<24 - 24-40 - \>40\| 20. Urea (mg\\dl): - 40-50 - 50-60 - \>60 21. eGFR (ml\\min\\1.73 m²): - ≥90 - 60-89 - \<60 22. Early AKI Developed (According to KDIGO Criteria): ☐ Yes ☐ No 23. If Yes, Stage of AKI: ☐**Stage 1:** serum creatinine Increase by ≥0.3 mg/dL within 48 hoursOR 1.5--1.9 times increase from baseline; Urine output \<0.5 mL/kg/hr for 6--12 hours. ☐**Stage 2:** increase in serum creatinine by 2.0--2.9 times from baselineOR Urine output \<0.5 mL/kg/hr for ≥12 hours ☐ **Stage 3:** increase in serum creatinine by 3.0 times from baseline OR Serum creatinine ≥4.0 mg/Dl OR Dialysis ;Urine output \<0.3 mL/kg/hr for ≥24 hours OR Anuria for ≥12 hours (Sellin et al., 2024) [Command succeeded with exit code 0]