Cardiac Patient Posted for Non-Cardiac Surgery - Anesthetic Management

Overview

1. PREOPERATIVE EVALUATION

Step-wise ACC/AHA Algorithmic Approach

1. Is surgery emergent? - If yes, proceed with risk stratification and postoperative surveillance; no time for testing.
2. Active cardiac conditions? - Must be treated FIRST before elective surgery:
   • Unstable angina / recent MI (within 60 days)
   • Decompensated heart failure (NYHA Class IV)
   • Significant arrhythmias (high-degree AV block, symptomatic VT, AF with rapid rate)
   • Severe valvular disease (severe AS: AVA <1 cm², severe symptomatic MR)
3. Surgical risk category:
   • Low risk (<1% MACE): Superficial, endoscopy, cataract
   • Intermediate risk (1-5%): Abdominal, orthopedic, head & neck
   • High risk (>5%): Aortic/major vascular, peripheral vascular
4. Functional capacity (METs):
   • ≥4 METs (climb stairs, walk uphill) = adequate; proceed without further testing
   • <4 METs = poor functional capacity; consider further testing
5. RCRI (Revised Cardiac Risk Index) - 1 point each for:
   • High-risk surgery
   • History of IHD
   • History of heart failure
   • History of cerebrovascular disease
   • Diabetes on insulin
   • Serum creatinine >2 mg/dL
   • Score 0-1 = low risk; ≥3 = high risk (~11% MACE)
6. ACS NSQIP - alternative risk calculator for perioperative MACE.

Biomarkers

• BNP / NT-proBNP: Prognostic value for perioperative cardiac risk; ACC/AHA does not yet recommend routine use for decision-making
• Cardiac troponin: Measure only when signs/symptoms of myocardial ischemia; routine screening of asymptomatic patients not recommended
• (Fuster and Hurst's The Heart, 15th Ed.)

Investigations

• ECG (baseline for patients with known CVD or risk factors)
• Echo - for HF assessment, valvular disease
• Stress testing - only if it will change management AND functional capacity is unknown/poor

Anticoagulant/Antiplatelet Therapy

• Aspirin: Continue unless bleeding risk outweighs benefit; generally continue for cardiac stents
• Dual antiplatelet (DAPT):
  • Bare metal stent (BMS): Wait at least 30 days before elective surgery
  • Drug-eluting stent (DES): Wait at least 6-12 months before elective surgery
• Warfarin: Bridge therapy with LMWH in high-risk patients (mechanical valves, AF with high CHADS₂)
• DOACs: Hold 24-48 hours pre-op (renal function dependent)

2. INTRAOPERATIVE ANESTHETIC MANAGEMENT

Choice of Anesthetic Technique

General Anesthesia (GA)

• Intravenous induction agents:
  • Propofol - vasodilation and myocardial depression; reduce dose in cardiac patients
  • Etomidate - most hemodynamically stable induction agent; drug of choice in compromised cardiac function (does not depress myocardium significantly)
  • Ketamine - sympathomimetic (raises HR, BP); useful in low-output states but avoid in tachycardia/ischemia
• Inhalational agents:
  • Volatile agents (sevoflurane, desflurane, isoflurane) - all cause dose-dependent myocardial depression and vasodilation
  • Ischemic preconditioning effect: volatile agents (especially sevoflurane, isoflurane) confer myocardial protection via preconditioning
  • Desflurane may cause tachycardia with rapid increases - avoid in ischemic heart disease
• Opioids - fentanyl, remifentanil: minimal hemodynamic effects; useful adjuncts to reduce volatile agent requirements
• Neuromuscular blockade - prefer agents with minimal cardiovascular side effects; rocuronium (preferred); vecuronium (minimal cardiac effects); succinylcholine causes transient bradycardia

Neuraxial and Regional Anesthesia

• Spinal anesthesia: Profound sympathetic block → hypotension; use cautiously in cardiac patients; treat hypotension promptly (phenylephrine preferred over ephedrine for IHD)
• Epidural anesthesia: Slower onset of sympathetic block; allows titration; used for thoracic epidural analgesia (TEA) which has cardioprotective effect
  • Thoracic epidural: reduces cardiac preload and afterload; useful in IHD patients; reduces perioperative MI incidence
• Neuraxial + anticoagulation: Strict ASRA guidelines must be followed (e.g., hold LMWH 12h before neuraxial block)
• Regional/nerve blocks: Excellent for peripheral procedures; avoids systemic effects of GA

3. INTRAOPERATIVE MONITORING

Non-invasive (Standard)

• 5-lead ECG (leads II and V5 - maximum sensitivity for ischemia detection)
• Pulse oximetry
• Non-invasive BP (every 1-5 min)
• Capnography (ETCO₂)
• Temperature monitoring

Invasive Monitoring (for high-risk patients)

• Arterial line (A-line): Beat-to-beat BP; waveform analysis; blood gas sampling; for all high-risk cardiac patients
• Central venous catheter (CVC): CVP monitoring; vasoactive drug infusion
• Pulmonary artery catheter (PAC): For severe HF, pulmonary hypertension, complex procedures; allows measurement of PCWP, CO, SVR; controversial routine use
• Transesophageal Echocardiography (TEE): Real-time cardiac function; wall motion abnormality detection (ischemia); valvular function; volume status; highly sensitive for ischemia; increasingly standard for high-risk cardiac patients
• Transthoracic Echocardiography (TTE): Preoperative baseline; less useful intraoperatively
• Cardiac output / Goal-Directed Therapy (GDT): FloTrac, LiDCO, PICCO; optimize fluid management and cardiac output in real-time
• (Fuster and Hurst's The Heart, 15th Ed.; Miller's Anesthesia, 10th Ed.)

4. INTRAOPERATIVE GOALS

• Avoid tachycardia (increases O₂ demand, reduces diastolic filling)
• Avoid hypotension (MAP >65 mmHg; coronary perfusion pressure depends on diastolic BP)
• Avoid hypertension (increases afterload and O₂ demand)
• Maintain normovolemia (euvolemia; avoid fluid overload in HF)
• Maintain normothermia (hypothermia → coagulopathy, arrhythmias)
• Adequate analgesia (pain → catecholamine surge → tachycardia, hypertension)
• Optimize oxygen delivery; maintain Hb >8-10 g/dL in ischemic heart disease

5. POSTOPERATIVE MANAGEMENT

Cardiac Complications

• Myocardial Infarction (MI): Most common cause of perioperative cardiac death; peaks on POD 3; typically pain-free (silent); diagnosed by troponin rise
• Heart Failure: Fluid shifts, fluid overload, myocardial dysfunction
• Arrhythmias: Common; manage with rate control, cardioversion as needed
• Deep Vein Thrombosis/PE: Anticoagulation strategy important

Enhanced Recovery After Surgery (ERAS)

• Multimodal analgesia to reduce opioid requirements
• Early mobilization
• Optimal fluid management
• Nausea/vomiting prophylaxis
• (Fuster and Hurst's The Heart, 15th Ed.)

Medications to Continue Perioperatively

• Beta-blockers: Continue; abrupt withdrawal increases risk of perioperative MI; if starting new beta-blocker, begin ≥1 week before surgery (not on day of surgery)
• Statins: Continue perioperatively (plaque stabilization effect)
• ACE inhibitors / ARBs: Consider holding on morning of surgery (risk of refractory hypotension with induction); restart as soon as hemodynamically stable
• Nitrates: Continue
• Antiarrhythmics: Continue

Summary Table: Key Points for 5-Mark Answer

• Fuster and Hurst's The Heart, 15th Edition - Chapter 73: Perioperative Anesthetic Management of Patients with CVD
• Miller's Anesthesia, 10th Edition - Chapter 52: Anesthesia and the Cardiac Patient for Noncardiac Surgery
• ACC/AHA 2014 Perioperative Guidelines for Noncardiac Surgery

Cardiac Risk Index

1. GOLDMAN'S CARDIAC RISK INDEX (Original, 1977)

Goldman's 9 Factors and Points:

Goldman Classes and Cardiac Complication Risk:

• (Miller's Anesthesia, 10th Ed.)

2. DETSKY MODIFIED CARDIAC RISK INDEX

• Modification of Goldman's CRI
• Adds unstable angina and pulmonary edema as separate weighted items
• Uses a nomogram to calculate pretest probability of complications based on surgery type
• Was advocated as starting point for risk stratification in American College of Physicians guidelines
• (Miller's Anesthesia, 10th Ed.)

3. LEE'S REVISED CARDIAC RISK INDEX (RCRI) - Current Standard

RCRI - 6 Predictors:

RCRI Score and Risk of Major Cardiac Events (MACE):

• (Miller's Anesthesia, 10th Ed.; Barash Clinical Anesthesia, 9th Ed.)

RCRI Risk by Procedure Type:

4. ACS NSQIP / MICA (Newer Tools)

5. Comparison: Goldman vs RCRI

6. Clinical Application

1. Emergency surgery? → Proceed, manage perioperatively
2. Active cardiac conditions? → Stabilize first
3. Low-risk surgery? → Proceed
4. Good functional capacity (≥4 METs)? → Proceed
5. RCRI ≥2 + poor functional capacity → Consider further testing (stress imaging) only if result will change management

• Miller's Anesthesia, 10th Ed. - Chapter 27 & 28
• Barash Clinical Anesthesia, 9th Ed. - Chapter 23
• Bailey and Love's Short Practice of Surgery, 28th Ed. - Chapter 21
• Lee TH et al., Circulation 1999;100:1043-1049
• Goldman L et al., NEJM 1977;297:845-850

Perioperative MI (POMI) - Pathophysiology

Classification of AMI Types (Universal Definition)

KEY PATHOPHYSIOLOGICAL MECHANISMS IN DETAIL

1. SURGICAL STRESS RESPONSE (The Trigger)

Surgery / Tissue Injury
        ↓
Hypothalamic-Pituitary-Adrenal (HPA) Axis Activation
        +
Sympatho-adrenal Activation
        ↓
↑ Catecholamines (adrenaline, noradrenaline)
↑ Cortisol, ↑ Glucagon
        ↓
Tachycardia + Hypertension + Vasoconstriction

2. PRO-INFLAMMATORY / PRO-COAGULANT STATE (Unique to Surgery)

• ↑ IL-6, IL-1, TNF-α → C-reactive protein surge
• ↑ Fibrinogen, ↑ Factor VIII, ↑ vWF
• ↓ Fibrinolysis (↑ PAI-1)
• Platelet activation enhanced by surgical trauma and catecholamines
• Endothelial dysfunction from ischemia-reperfusion and inflammation

3. TYPE 1 PATHWAY - Plaque Rupture

Pre-existing Vulnerable Atherosclerotic Plaque
(lipid-rich core, thin fibrous cap)
        ↓
Catecholamine surge → ↑ Heart rate + ↑ Blood pressure
        ↓
↑ Shear stress on coronary vessel wall
        +
Inflammatory mediators (MMP activation → cap thinning)
        ↓
PLAQUE RUPTURE / EROSION
        ↓
Subendothelial collagen + lipid core exposed
        ↓
Platelet adhesion → Activation → Aggregation (GP IIb/IIIa)
        ↓
Fibrin deposition (↑ coagulation factors perioperatively)
        ↓
THROMBUS FORMATION
        ↓
Complete coronary occlusion
        ↓
STEMI (transmural infarct)

4. TYPE 2 PATHWAY - Supply-Demand Mismatch

DECREASED O₂ SUPPLY:
- Tachycardia → ↓ diastolic filling time → ↓ coronary flow
- Hypotension → ↓ coronary perfusion pressure (CPP = DBP - LVEDP)
- Anemia → ↓ O₂ carrying capacity
- Hypoxia / Respiratory depression
- Coronary artery spasm (cold, pain, catecholamines)
- Hypovolemia

        +

INCREASED O₂ DEMAND:
- Tachycardia (most important - doubles O₂ demand)
- Hypertension → ↑ wall stress / afterload
- Pain → catecholamine surge
- Shivering / Hypothermia → ↑ metabolic demand
- Anaemia compensation (↑ CO)

        ↓

O₂ Supply < O₂ Demand

        ↓

Subendocardial ischemia first
(subendocardium most vulnerable - highest wall stress, lowest perfusion)

        ↓

ST depression, T-wave changes, troponin rise

        ↓

NSTEMI (non-transmural, demand-type)

5. COMMON FINAL PATHWAY

Myocardial cell death (irreversible ischemia >20 min)
        ↓
Troponin I/T release (peaks POD 1-3)
        ↓
┌─────────────────────────────────────────┐
│                                         │
Myocardial Stunning          Myocardial Hibernation
(reversible dysfunction       (chronic ischemia,
 after brief ischemia)        viable but non-contractile)
│                                         │
└─────────────────────────────────────────┘
        ↓
LV systolic dysfunction → ↓ EF
        ↓
┌───────────────────────────────────────────────────────┐
│               COMPLICATIONS                           │
│  Ventricular arrhythmias (VF - most common early death│
│  Acute heart failure / cardiogenic shock              │
│  Mechanical complications (papillary muscle rupture,  │
│  free wall rupture, VSD)                              │
│  Reinfarction                                         │
└───────────────────────────────────────────────────────┘

TIMING OF PERIOPERATIVE MI

CLINICAL FEATURES (Often Silent Perioperatively)

• 60-90% are SILENT in the perioperative period - pain masked by residual analgesia, sedation, general anesthesia
• Diagnosis relies on: troponin rise + ECG changes ± symptoms
• May present as: unexplained hypotension, new arrhythmia, ST changes, heart failure, cardiac arrest
• MINS (Myocardial Injury after Non-cardiac Surgery) = troponin elevation without symptoms - still associated with 30-day mortality

RISK FACTORS AMPLIFYING PERIOP MI RISK

• Morgan & Mikhail's Clinical Anesthesiology, 7th Ed. - Chapter on Acute MI Pathophysiology
• Fuster and Hurst's The Heart, 15th Ed. - Chapter 73
• Miller's Anesthesia, 10th Ed. - Chapter 27/28