Chest Pain and Its Management - For MD Anaesthesia Exam

Sourced from Miller's Anesthesia (10e), Barash's Clinical Anesthesia (9e), and Morgan & Mikhail's Clinical Anesthesiology (7e)

1. OVERVIEW AND EPIDEMIOLOGY

1. Preoperative - in evaluation of the patient with suspected or known ischaemic heart disease
2. Intraoperative - as a manifestation of ongoing myocardial ischaemia
3. Postoperative (PACU/ICU) - as a signal of perioperative myocardial ischaemia/infarction (MI)

2. PATHOPHYSIOLOGY OF MYOCARDIAL ISCHAEMIA (The Basis of Ischaemic Chest Pain)

Morgan & Mikhail (7e):

"Myocardial ischaemia results from metabolic oxygen demand that exceeds the oxygen supply. Ischaemia can therefore result from increased myocardial metabolic demand, reduced myocardial oxygen delivery, or a combination of both."

• Coronary arterial atherosclerosis (most common - CAD responsible for ~25% of all deaths in Western societies)
• Coronary thrombosis or vasospasm
• Severe hypertension or tachycardia (increases demand AND reduces supply by shortening diastolic filling time)
• Severe hypotension, hypoxaemia, or anaemia
• Severe aortic stenosis or regurgitation

3. CLASSIFICATION OF CHEST PAIN / ANGINAL SYNDROMES

A. Chronic Stable Angina (Morgan & Mikhail, 7e)

• Substernal, exertional chest pain
• Radiates to neck or arm
• Relieved by rest or nitroglycerin
• Variations: epigastric, back, neck pain, or transient dyspnoea ("anginal equivalent")
• Nonexertional and silent ischaemia are common, especially postoperatively
• Diabetics have increased incidence of silent ischaemia

B. Unstable Angina (Morgan & Mikhail, 7e)

1. Abrupt increase in severity, frequency (>3 episodes/day), or duration - "crescendo angina"
2. Angina at rest
3. New onset angina within past 2 months with severe or frequent episodes (>3/day)

C. Acute Coronary Syndrome (Miller's Anesthesia, 10e)

1. Diagnosis be made
2. Treatment commenced
3. Triage to the right facility

4. PREOPERATIVE EVALUATION OF CHEST PAIN / ISCHAEMIC HEART DISEASE

A. History (Morgan & Mikhail, 7e)

• Exercise tolerance, fatigability, pedal oedema, dyspnoea (exertional/orthopnea/PND)
• Chest pain - character, radiation, triggers, relieving factors
• Prior interventions (valvotomy, valve replacement, CABG, PCI)
• Neurological symptoms (embolic phenomena)
• Current medications

B. ECG Stress Testing (Barash, 9e)

• Exercise ECG: sensitivity 70-80%, specificity 60-75% for CAD
• Most cost-effective, least invasive method
• Positive test = patient at risk during tachycardia
• Greatest risk: ischaemia after only mild exercise
• If patient can exercise without ischaemic symptoms → no further testing needed

C. Pharmacological Stress Testing (Barash, 9e)

• Dobutamine Stress Echocardiography (DSE): Dobutamine increases myocardial O2 demand; new/worsening regional wall motion abnormalities = positive test. Greatest risk = RWMA at low heart rates.
• Dipyridamole/Adenosine/Regadenon MPI (Thallium-201 / Tc-99m / Rubidium-82): Coronary vasodilator to assess flow heterogeneity. Redistribution defect = positive.

• Normal DSE or MPI → high negative predictive value for perioperative MI/death
• Moderate to large areas of ischaemia → increased risk of perioperative MI/death
• Fixed perfusion defect → prior MI, limited predictive value but increased long-term risk

• Active cardiac conditions: unstable angina, CHF, significant arrhythmias, severe valvular disease
• Vascular or high-risk surgery + multiple clinical risk factors + poor functional capacity (< 4 METs)
• NOT recommended routinely for low-risk patients

D. Holter Monitoring (Morgan & Mikhail, 7e)

• Frequent ischaemic episodes on preoperative Holter correlate well with intraoperative and postoperative ischaemia
• No ischaemia on Holter → excellent negative predictive value for postoperative cardiac complications

E. Coronary Angiography (Barash, 9e)

• Best method for defining coronary anatomy
• Also assesses ventricular and valvular function, haemodynamic indices
• Not recommended routinely preoperative per ACC/AHA guidelines
• Critical stenosis delineates area at risk, but many perioperative MIs result from acute thrombosis of a non-critical stenosis

5. PREOPERATIVE MEDICATIONS - WHAT TO DO

Morgan & Mikhail (7e):

"Preoperative medications should generally be continued until the time of surgery."

• Beta-blockers: Do NOT withdraw abruptly - sudden withdrawal can precipitate rebound increase in ischaemic episodes
• Statins: Should be continued in the perioperative period
• Nitrates: Prophylactic transdermal or IV nitroglycerin in patients NOT previously on long-term nitrates and without ongoing ischaemia = no benefit. Transdermal absorption is erratic perioperatively.

6. INTRAOPERATIVE MANAGEMENT OF ISCHAEMIC CHEST PAIN / ISCHAEMIA

A. Core Objective (Morgan & Mikhail, 7e):

"The overwhelming priority in managing patients with ischaemic heart disease is maintaining a favourable myocardial supply-demand relationship."

B. Haemodynamic Goals:

• Control autonomic-mediated ↑ heart rate and ↑ BP with: deeper anaesthesia, adrenergic blockade, vasodilators
• Avoid excessive ↓ coronary perfusion pressure or ↓ arterial oxygen content
• Higher diastolic pressures preferred in patients with high-grade coronary occlusions
• Avoid excessive ↑ LVEDP (fluid overload) → ↑ ventricular wall tension → ↓ subendocardial perfusion
• Haemoglobin: most clinicians avoid Hb < 7 g/dL (anaemia → tachycardia → worsens supply-demand)
• Tachycardia = most dangerous intraoperative event: both increases demand AND reduces supply

C. ACC/AHA Recommendations - Table Summary (Morgan & Mikhail, 7e):

D. Coronary Steal and Volatile Anaesthetics (Barash, 9e):

• Isoflurane (and most volatile agents) increases coronary blood flow beyond myocardial O2 demand → potential for "steal" (diversion of blood from poorly perfused to better-perfused territory)
• However, clinical outcome studies have not found an association between isoflurane and increased perioperative MI/death in CABG patients
• Sevoflurane: similar ischaemic outcomes to isoflurane in CAD patients
• Desflurane without opioids in CAD patients undergoing CABG → significant ischaemia requiring beta-blockers (one exception study)
• Conclusion: determinants of O2 supply-demand are far more important than the choice of anaesthetic

E. Cardioprotection by Volatile Anaesthetics (Barash, 9e):

• Volatile agents given before (preconditioning) or immediately after ischaemia (postconditioning) mimic ischaemic preconditioning
• Mechanism: volatile agents → mitochondrial electron transport alteration → reactive oxygen species formed → protein kinase C activation → KATP channel opening
• ~30-40% of cardioprotection is related to this mechanism

7. POSTOPERATIVE CHEST PAIN / MYOCARDIAL ISCHAEMIA IN THE PACU

A. Why Chest Pain is Often Absent Postoperatively (Miller's Anesthesia, 10e):

"Myocardial ischaemia is rarely accompanied by chest pain in the recovery room secondary to the fact that patients are still emerging from anaesthesia in the immediate postoperative period and are also still under the influence of residual medication effects, especially analgesics."

B. Myocardial Injury After Noncardiac Surgery (MINS) (Miller's Anesthesia, 10e):

• Defined as: elevated postoperative troponin levels without clinical symptoms or ECG changes, with no other nonischaemic cause (e.g., not due to chronic troponin elevation, PE, sepsis, rapid AF)
• In a recent multicenter study: 93% of patients with MINS did not experience any symptoms
• Elevated hsTnT without ischaemic features in first 3 days after noncardiac surgery → significantly increased 30-day mortality

C. Risk Quantification (Miller's Anesthesia, 10e):

• Over 1 million people die every year after noncardiac surgery; MI is the most common cardiovascular complication
• Per the Revised Goldman Cardiac Risk Index: risk of adverse cardiac event up to 5.4% in patients with ≥3 risk factors

D. Evaluation of Postoperative Chest Pain (Miller's Anesthesia, 10e):

• 12-lead ECG
• Troponin level (AHA/ACC recommend troponin for all patients with ECG changes of ischaemia OR typical ischaemic chest pain after surgery)
• Physical examination
• Point-of-care ultrasonography (assess cardiac function, valvular/wall motion abnormalities)

E. Treatment of Postoperative Myocardial Ischaemia (Miller's Anesthesia, 10e):

1. Notify the primary surgical team immediately
2. Cardiology consult
3. Optimise BP, heart rate, and oxygenation
4. If no absolute contraindications:
   • Nitroglycerin (reduce preload/ischaemia)
   • Beta-blocker (reduce heart rate and O2 demand)
   • Statin
   • Aspirin
5. Opioid for pain (reduces sympathetic drive and O2 demand)
6. Correct anaemia if present
7. Code cart at bedside (preparation for decompensation)
8. Echocardiography / point-of-care USS (guide haemodynamic management, consider IABP)
9. Consider further interventions (discussed as a team): fibrinolysis, PCI, revascularisation
   • NOTE: A mutual approach between surgeon + cardiologist + anaesthesiologist + patient is required to weigh risks of anticoagulation/antiplatelet therapy in the immediate postoperative setting

8. PAIN AND MYOCARDIAL ISCHAEMIA - THE TWO-WAY RELATIONSHIP

Morgan & Mikhail (7e) - Effects of Acute Pain on the Cardiovascular System:

• Acute pain causes: hypertension, tachycardia, enhanced myocardial irritability, increased SVR
• Cardiac output increases in normal patients but may decrease in patients with compromised ventricular function
• "Because of the increase in myocardial oxygen demand, pain can worsen or precipitate myocardial ischaemia"

• Neuraxial analgesia reduces perioperative MI in abdominal aortic surgery
• Untreated postoperative pain → sympathetic activation → tachycardia → ischaemia → chest pain → more ischaemia (vicious cycle)

9. CHEST PAIN IN SPECIFIC PERIOPERATIVE SCENARIOS

A. Unstable Tachycardia (Morgan & Mikhail, 7e):

B. Postoperative Shivering and Hypothermia (Morgan & Mikhail, 7e):

• Shivering increases O2 consumption up to fivefold → associated with increased risk of myocardial ischaemia
• Hypothermia = arrhythmias, hypertension, impaired haemostasis, increased transfusion requirements, and increased incidence of myocardial ischaemia
• Treatment: forced-air warming device (preferred), warming lights, or heating blankets
• Shivering treatment: meperidine 12.5-25 mg IV in adults; better = maintain normothermia intraoperatively

C. Stellate Ganglion Block (Morgan & Mikhail, 7e):

• Used for patients with head, neck, arm, and upper chest pain (including vasospastic angina)
• Commonly referred to as stellate block; blocks sympathetic supply to the upper extremity and heart

D. Chest Pain in Sickle Cell Anaemia (Miller's Anesthesia, 10e):

• Acute Chest Syndrome: bilateral infiltrates, chest pain, fever, wheezing - ARDS-type course
• Hemolytic crises: acute drop in Hb → further worsens myocardial O2 delivery

10. PREHOSPITAL ACS MANAGEMENT (EMS / Anaesthesiologist Perspective)

Miller's Anesthesia (10e):

• Essential for assessment and triage of chest pain patients
• Enables diagnosis of STEMI in prehospital setting
• Prehospital ECG reduces time from presentation to reperfusion; adjusted risk of mortality lower with ECG use

• Primary PCI = treatment of choice for STEMI if achievable within 90 minutes of onset
• If mechanical reperfusion not possible within that window (geographic isolation / non-PCI hospital) → fibrinolysis followed by PCI within 24 hours
• Prehospital fibrinolysis by paramedics = practical, feasible, with favorable clinical outcomes

11. EXAM SUMMARY TABLE

• Miller's Anesthesia, 2-Volume Set, 10e - Chapters on Prehospital Care (Block 26), PACU/Recovery (Block 32)
• Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e - Chapter on Pharmacology of Volatile Agents (Block 6), Preoperative Cardiac Evaluation (Block 7)
• Morgan and Mikhail's Clinical Anesthesiology, 7e - Chapter on Ischaemic Heart Disease (Block 3), Pain Physiology (Block 7), PACU (Block 9)