Pre-operative Cardiovascular Assessment

Quick Answer

Pre-operative cardiovascular assessment aims to identify patients at increased risk of perioperative cardiac complications and optimize those with active cardiac conditions. The 2014 ACC/AHA Guidelines provide a stepwise algorithm: assess surgical urgency, evaluate for active cardiac conditions, estimate cardiac risk using validated indices (RCRI, NSQIP), assess functional capacity (≥4 METs = low risk), and determine need for further testing. NYHA Class I-II typically indicates adequate functional capacity (>4 METs), while Class III-IV (<4 METs) warrants further evaluation. Key predictors include high-risk surgery, ischemic heart disease, congestive heart failure, cerebrovascular disease, insulin-dependent diabetes, and renal impairment. Biomarkers (NT-proBNP, high-sensitivity troponin) and focused cardiac ultrasound are increasingly used for risk stratification. Australian guidelines align with ACC/AHA but emphasize early multidisciplinary involvement and Indigenous health considerations.

Clinical Overview

Definition and Epidemiology

Pre-operative cardiovascular assessment is the systematic evaluation of a patient's cardiac status prior to noncardiac surgery to identify risk factors, optimize cardiac function, and guide perioperative management to reduce morbidity and mortality. Major adverse cardiac events (MACE) include myocardial infarction, cardiac arrest, cardiac death, severe arrhythmias, and congestive heart failure requiring intervention. The incidence of perioperative cardiac complications varies from 0.5% to 2% in unselected populations but can exceed 10% in high-risk groups undergoing major surgery. [1,2]

Pathophysiology

Perioperative cardiac stress results from sympathetic activation, fluid shifts, pain, and inflammation. Surgical stress increases myocardial oxygen demand while simultaneously compromising supply through tachycardia (reduced diastolic filling time), hypertension, and potential blood loss. Patients with coronary artery disease may develop myocardial ischemia when oxygen demand exceeds supply. Postoperative hypercoagulability increases thrombotic risk. Type 2 myocardial infarction (supply-demand mismatch) is more common than type 1 (plaque rupture) perioperatively. [3,4]

Pre-operative Assessment Considerations

History should focus on exercise tolerance, angina symptoms, dyspnea, syncope, palpitations, and functional status. NYHA classification grades symptom severity: Class I (no limitation with ordinary activity), Class II (slight limitation, comfortable at rest), Class III (marked limitation, less than ordinary activity causes symptoms), Class IV (unable to carry out physical activity without discomfort, symptoms at rest). Physical examination evaluates blood pressure, heart sounds (murmurs, S3 gallop), peripheral edema, jugular venous pressure, and peripheral circulation. [5,6]

ECG is recommended for patients with known cardiovascular disease, risk factors, or undergoing intermediate-to-high-risk surgery. Resting echocardiography is indicated for symptomatic heart failure, valvular disease with murmurs, or unexplained dyspnea. Stress testing (exercise, pharmacologic) is reserved for patients with poor or unknown functional capacity (<4 METs) undergoing high-risk surgery when results would change management. Coronary CT angiography may be considered in selected patients with intermediate pre-test probability. [7,8]

Intraoperative Management Principles

Patients with cardiovascular disease require careful induction to minimize hemodynamic fluctuations. Agents with hemodynamic stability (etomidate, ketamine, or careful titration of propofol) are preferred. Opioids blunt sympathetic response to laryngoscopy. Volatile agents provide myocardial preconditioning but cause dose-dependent depression. Maintain adequate perfusion pressure (within 20% of baseline), heart rate (60-80 bpm), and oxygen delivery. Avoid tachycardia, hypertension, hypotension, and arrhythmias. Consider invasive arterial pressure monitoring for high-risk patients. [9,10]

Post-operative Care Priorities

High-risk patients require monitoring in a high-dependency or intensive care unit for 24-48 hours. Continuously monitor ECG for ischemia (ST-segment changes, arrhythmias). Serial cardiac biomarkers (troponin) at 6-12 hours and 24 hours postoperatively detect myocardial injury. Maintain adequate oxygenation, normothermia, pain control, and normovolemia. Continue beta-blockers and statins unless contraindicated. Early mobilization when appropriate. [11,12]

Anaesthetic Management

Detailed Anaesthetic Technique

For patients with stable coronary artery disease and optimized therapy, a balanced anaesthetic technique is appropriate. Pre-medication with anxiolytics should be used cautiously, as oversedation may cause respiratory depression and hypoxia. Beta-blockers should be continued through the perioperative period in patients on chronic therapy; abrupt withdrawal can cause rebound tachycardia and hypertension. Statins should also be continued unless contraindicated. ACE inhibitors and ARBs are often withheld on the morning of surgery to prevent intraoperative hypotension, though evidence on this practice is mixed. [13,14]

Induction should be gentle and gradual. Propofol (1-2 mg/kg) can be used but may cause hypotension. Etomidate (0.2-0.3 mg/kg) causes minimal hemodynamic changes but may cause adrenal suppression. Ketamine (1-2 mg/kg) maintains cardiovascular stability but causes tachycardia and hypertension. In patients with severe cardiac dysfunction, consider a titrated induction with small incremental doses or a combination of ketamine and benzodiazepine. Opioids (fentanyl 2-5 mcg/kg, alfentanil 10-20 mcg/kg, or remifentanil infusion) blunt the sympathetic response to laryngoscopy and intubation. [15,16]

Maintenance Strategies

Maintenance of anaesthesia in cardiac patients aims to minimize hemodynamic variability. Volatile agents (isoflurane, sevoflurane, desflurane) provide dose-dependent depression of myocardial contractility and vasodilation. Isofllurane may cause coronary steal syndrome in patients with coronary artery disease, making sevoflurane or desflurane preferred. Volatile agents also provide myocardial preconditioning, reducing myocardial ischemia and infarct size. Total intravenous anaesthesia (TIVA) with propofol and remifentanil offers rapid titratability and may be beneficial in patients at risk of postoperative nausea and vomiting. [17,18]

Neuromuscular blockade should be monitored with quantitative devices. Non-depolarizing agents (rocuronium, vecuronium) have minimal cardiovascular effects. Succinylcholine causes bradycardia in children and tachycardia/dysrhythmias in adults. Reversal with sugammadex (rocuronium, vecuronium) or neostigmine/glycopyrrolate (non-sugammadex agents) must be timed to avoid residual paralysis that may compromise respiratory drive and oxygenation. [19,20]

Monitoring Requirements

Standard ASA monitoring is mandatory. For patients with significant cardiac disease, invasive arterial pressure monitoring is indicated to detect rapid changes and allow frequent blood sampling. Central venous pressure monitoring may be used for major surgery or patients with heart failure but has limitations in predicting fluid responsiveness. Pulse oximetry, capnography, and temperature monitoring are standard. Urine output, neuromuscular blockade, and depth of anaesthesia monitoring (BIS, Entropy) are used selectively. [21,22]

Intraoperative transesophageal echocardiography (TEE) provides real-time assessment of ventricular function, volume status, valvular function, and detection of ischemia (wall motion abnormalities). It is particularly useful in cardiac surgery, major vascular surgery, and high-risk noncardiac surgery. ST-segment analysis (automated or manual) should be used continuously for patients at risk of myocardial ischemia. [23,24]

Specific Drug Choices and Rationale

Propofol provides rapid, smooth induction with antiemetic properties but causes dose-dependent hypotension through vasodilation and decreased myocardial contractility. Etomidate offers hemodynamic stability with minimal effects on cardiovascular function but causes adrenal suppression and may increase mortality in critically ill patients. Ketamine maintains sympathetic tone, preventing hypotension, but may increase myocardial oxygen demand through tachycardia and hypertension. [25,26]

Opioids provide analgesia and blunting of sympathetic response. Fentanyl is widely used with a duration of 30-60 minutes. Alfentanil has a rapid onset (1-2 minutes) and short duration (10-20 minutes), making it useful for RSI. Remifentanil is an ultra-short-acting opioid (context-sensitive half-time of 3-5 minutes) that provides tight hemodynamic control and rapid emergence. Morphine and pethidine have long durations and histamine release causing hypotension. [27,28]

Volatile agents: Sevoflurane and desflurane have low blood-gas partition coefficients, allowing rapid titration and emergence. Isofllurane has a higher solubility and slower emergence but is inexpensive. All volatile agents cause dose-dependent myocardial depression and vasodilation. Nitrous oxide (N2O) provides analgesia and reduces volatile agent requirements but causes diffusion hypoxia, bowel distension, and should be avoided in patients with pneumothorax, bowel obstruction, or recent ophthalmic surgery. [29,30]

Perioperative Care

Pre-operative Preparation

Pre-operative optimization involves managing modifiable risk factors. Patients with unstable angina, decompensated heart failure, severe valvular disease, or significant arrhythmias require cardiology review and often postponement of elective surgery. Optimizing medical therapy includes ensuring adequate control of hypertension, heart failure, arrhythmias, and angina. Beta-blockers should be continued and may be initiated preoperatively in selected high-risk patients, though the optimal timing is debated. Statins should be continued; preoperative initiation may be considered in high-risk vascular surgery patients. [31,32]

Diabetic patients require careful glucose management. Target blood glucose should be 6-10 mmol/L perioperatively to avoid hypoglycemia and hyperglycemia complications. SGLT2 inhibitors should be withheld 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis. Insulin regimens may need adjustment. [33,34]

Patients with implanted cardiac devices (pacemakers, ICDs) require device interrogation and appropriate management. Pacemaker-dependent patients require magnet application or reprogramming to asynchronous mode during electrocautery. ICDs should have tachyarrhythmia therapy disabled intraoperatively with external defibrillation pads placed. [35,36]

Intraoperative Monitoring

High-risk cardiovascular patients benefit from advanced monitoring. Invasive arterial blood pressure monitoring allows beat-to-beat blood pressure measurement and arterial blood gas sampling. It is indicated for major surgery, patients with significant cardiovascular disease, hemodynamic instability, or anticipated large fluid shifts. Sites include radial, brachial, or femoral arteries. Radial artery has low complication rates but may be inaccurate during hypotension. Femoral artery provides more reliable readings but has higher complication risk. [37,38]

Central venous catheters measure central venous pressure, provide access for vasoactive drugs, and allow central venous oxygen saturation monitoring. Indications include major surgery, cardiac dysfunction, need for vasopressor/inotrope infusion, or anticipated fluid resuscitation. CVP has limitations in predicting fluid responsiveness. Central venous oxygen saturation (ScvO2) >65% suggests adequate oxygen delivery. [39,40]

Pulse contour analysis (PiCCO, FloTrac, LiDCO) provides continuous cardiac output, stroke volume variation, and systemic vascular resistance. These monitors use arterial waveform analysis to estimate stroke volume. They are useful for goal-directed fluid therapy in high-risk patients. Stroke volume variation >13% and pulse pressure variation >12% predict fluid responsiveness in mechanically ventilated patients with sinus rhythm and controlled ventilation. [41,42]

Post-operative Management

High-risk patients should be managed in an appropriate level of care (HDU or ICU). Pain control with multimodal analgesia reduces sympathetic activation and myocardial oxygen demand. Regional anaesthesia techniques, acetaminophen, NSAIDs (if not contraindicated), and low-dose opioids form the basis of multimodal analgesia. Avoid hypoxia, hypothermia, and anemia, as these increase myocardial oxygen demand and decrease supply. Target hemoglobin >80 g/L for most patients, >100 g/L for those with coronary artery disease. [43,44]

Early identification of myocardial injury after noncardiac surgery (MINS) is important. MINS is defined as myocardial injury due to ischemia within 30 days after surgery, manifested by elevated troponin with ischemic features or elevated troponin judged as due to ischemia without an alternative non-ischemic cause. Serial troponin measurements (6-12 hours postoperatively and 24 hours postoperatively) in high-risk patients detect MINS, which occurs in up to 20% of high-risk patients and is associated with increased 30-day mortality. [45,46]

Complications Prevention

Prevention strategies include careful patient selection, optimization of medical therapy, appropriate monitoring, and careful intraoperative management. Maintaining normothermia (36-37°C) reduces bleeding, infection, and cardiac complications. Adequate analgesia reduces sympathetic activation. Early ambulation reduces venous thromboembolism and improves respiratory function. Pharmacological prophylaxis with beta-blockers, statins, and aspirin in selected patients may reduce cardiovascular events. [47,48]

Discharge Planning

Discharge planning begins preoperatively. Patients with significant cardiac disease may require extended hospital stay, rehabilitation, or cardiology follow-up. Education about signs and symptoms of cardiac complications should be provided. Medication reconciliation ensures continuation of cardiac medications. Follow-up with primary care physician and appropriate specialists should be arranged. [49,50]

Complications & Management

Common Complications

Hypotension (systolic blood pressure <90 mmHg or >20% decrease from baseline) is common during induction due to vasodilation and myocardial depression. Treatment includes reducing or stopping anaesthetic agents, fluid bolus (250-500 mL crystalloid), and vasopressors (phenylephrine 50-100 mcg bolus or metaraminol 0.5-1 mg bolus). Persistent hypotension may require infusion (norepinephrine 0.05-0.3 mcg/kg/min, metaraminol 0.5-3 mg/hour). Underlying causes (hypovolemia, arrhythmia, pneumothorax, cardiac tamponade) must be identified and treated. [51,52]

Hypertension (systolic blood pressure >180 mmHg or >20% increase from baseline) can occur during emergence, noxious stimulation, or light anaesthesia. Treatment includes deepening anaesthesia, analgesia, and antihypertensive medications (labetalol 5-10 mg IV, hydralazine 5-10 mg IV, or nitroglycerin infusion). Poorly controlled intraoperative hypertension increases myocardial oxygen demand and risk of ischemia. [53,54]

Tachycardia (heart rate >100 bpm) increases myocardial oxygen demand and reduces diastolic filling time, potentially causing ischemia. Causes include light anaesthesia, pain, hypovolemia, hypoxia, hypercarbia, and anemia. Treatment involves identifying and treating the underlying cause. Beta-blockers (esmolol 25-50 mg bolus, metoprolol 1-5 mg bolus) are useful for sinus tachycardia. Vagal stimulation or carotid sinus massage may terminate supraventricular tachycardia. Antiarrhythmic medications (amiodarone) or cardioversion may be required for other arrhythmias. [55,56]

Bradycardia (heart rate <50 bpm) can occur due to vagal stimulation, opioid effects, beta-blockers, or conduction disease. Treatment depends on severity and hemodynamic consequences. Asymptomatic bradycardia may not require treatment. Symptomatic bradycardia with hypotension requires intervention. Atropine 0.5 mg IV (up to 3 mg total) is first-line. Glycopyrrolate 0.2-0.4 mg IV is an alternative. Refractory cases may require epinephrine 10-100 mcg bolus or pacing (transcutaneous or transvenous). [57,58]

Rare but Serious Complications

Myocardial infarction occurs in 1-5% of high-risk patients. Symptoms may be atypical or masked by anaesthesia and postoperative analgesia. ECG changes (ST elevation, depression, T-wave inversion), new bundle branch block, or ventricular arrhythmias suggest myocardial infarction. Cardiac biomarkers (troponin) should be measured. Management includes oxygen, nitrates, beta-blockers, antiplatelet therapy (aspirin, clopidogrel), statins, and urgent cardiology review. Reperfusion therapy (PCI or thrombolysis) may be indicated for ST-elevation myocardial infarction. [59,60]

Cardiac arrest occurs in 0.5-2 per 10,000 anaesthetics. Immediate management follows ACLS algorithm: assess responsiveness, call for help, start CPR (compressions 100-120/min, depth 5-6 cm, allow full recoil), defibrillate if shockable rhythm (VF/VT), give medications (epinephrine 1 mg every 3-5 minutes, amiodarone 300 mg for VF/VT after third shock), identify and treat reversible causes (4 H's: hypoxia, hypovolemia, hyper/hypokalemia, hypothermia; 4 T's: tension pneumothorax, tamponade, toxins, thrombosis). [61,62]

Stroke occurs in 0.1-0.5% of patients, with higher rates in cardiac and carotid surgery. Risk factors include age, hypertension, atrial fibrillation, carotid stenosis, and previous stroke. Prevention involves careful hemodynamic management (avoiding hypertension and hypotension), maintaining normoglycemia, and appropriate antithrombotic therapy. Treatment requires urgent neuroimaging (CT scan), supportive care, and stroke team involvement. Thrombolysis or thrombectomy may be indicated for ischemic stroke. [63,64]

Management Strategies

A systematic approach to hemodynamic instability includes ABCDE assessment, checking depth of anaesthesia, surgical stimulation, airway patency, breathing adequacy, circulation (blood pressure, heart rate, ECG, CVP, ScvO2), temperature, urine output, and blood loss. Consider drug effects, position changes, pneumoperitoneum, tourniquet release, and surgical complications (bleeding, air embolism, organ injury). Use appropriate monitoring (TEE, arterial line, CVP, cardiac output monitors). Involve help early. [65,66]

Prevention Measures

Prevention involves careful pre-operative assessment, appropriate monitoring, careful induction and maintenance, vigilant observation, prompt recognition of complications, and early intervention. Use pre-operative checklists, time-outs, and briefings. Maintain crew resource management principles. Have emergency equipment and medications readily available. Practice emergency drills regularly. [67,68]

ANZCA Final Exam Focus

Common SAQ Patterns

ANZCA Final Written SAQs often focus on:

• Pre-operative cardiovascular assessment algorithm (ACC/AHA guidelines)
• Risk stratification using RCRI, NSQIP, or other indices
• Interpretation of functional capacity (METs, NYHA class)
• Indications for cardiac testing (stress testing, echocardiography, coronary CT)
• Perioperative management of specific cardiac conditions (ischemic heart disease, heart failure, valvular disease, arrhythmias)
• Choice of anaesthetic technique and monitoring for high-risk patients
• Management of intraoperative hemodynamic complications

Clinical Viva Question Themes

Clinical viva scenarios may present:

• Patient with known coronary artery disease undergoing major noncardiac surgery
• Patient with symptomatic heart failure requiring emergency surgery
• Patient with severe aortic stenosis requiring noncardiac surgery
• Patient with recent myocardial infarction requiring urgent surgery
• Intraoperative myocardial ischemia management
• Interpretation of TEE findings in cardiac patients
• Postoperative myocardial injury after noncardiac surgery (MINS)

Management Algorithm Requirements

Examiners expect systematic approach to cardiovascular assessment:

1. Assess surgical urgency (emergency, urgent, elective)
2. Identify active cardiac conditions (unstable angina, decompensated heart failure, severe valvular disease, arrhythmias)
3. Estimate cardiac risk using validated index (RCRI)
4. Assess functional capacity (exercise tolerance, METs)
5. Determine need for further cardiac testing
6. Optimize medical therapy
7. Plan anaesthetic technique and monitoring
8. Manage postoperative care appropriately

Critical Points Examiners Look For

• Understanding of NYHA classification and functional capacity (≥4 METs vs <4 METs)
• RCRI components and interpretation (risk prediction)
• ACC/AHA guideline algorithm and evidence base
• Role of biomarkers (NT-proBNP, troponin) in risk stratification
• Indications for pre-operative cardiac testing and revascularization
• Choice of anaesthetic agents and rationale
• Appropriate monitoring for high-risk patients
• Management of intraoperative hemodynamic instability
• Recognition and management of MINS
• Perioperative medication management (beta-blockers, statins, ACE inhibitors, SGLT2 inhibitors)
• Indigenous health considerations in cardiovascular risk assessment

Australian/NZ Guidelines

ARC/ANZCOR Recommendations

While ARC/ANZCOR guidelines primarily focus on resuscitation, perioperative cardiac arrest management follows ANZCOR ALS algorithms. ANZCOR recommends:

• High-quality chest compressions (100-120/min, depth 5-6 cm, allow full recoil, minimize interruptions)
• Early defibrillation for shockable rhythms (VF/VT)
• Epinephrine 1 mg IV every 3-5 minutes for non-shockable rhythms
• Capnography to confirm and monitor endotracheal tube placement
• Post-cardiac arrest care (targeted temperature management, hemodynamic optimization, percutaneous coronary intervention if indicated)

Therapeutic Guidelines Australia

Therapeutic Guidelines: Cardiovascular provides recommendations for perioperative management:

• Continue beta-blockers in patients on chronic therapy
• Continue statins perioperatively (hold on day of surgery if concerned about interactions)
• Consider initiating beta-blockers in high-risk patients (start at least 1 week before surgery, titrate to heart rate 60-80)
• Withhold ACE inhibitors and ARBs on morning of surgery (optional, based on institutional practice)
• Hold SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic ketoacidosis
• Continue antiplatelet agents in patients with coronary stents (specific recommendations based on stent type and time since implantation)

Local Protocols

Individual hospitals have specific protocols based on national guidelines and local resources. Common protocols include:

• Pre-operative anaesthetic assessment clinics
• Cardiac evaluation pathways (cardiology consultation, stress testing, coronary angiography)
• Perioperative beta-blocker initiation protocols
• MINS screening and management pathways
• Postoperative care pathways for high-risk patients

Australian Drug Availability

Australia has access to standard anaesthetic agents:

• Induction agents: propofol, etomidate, ketamine, thiopentone (limited availability)
• Volatile agents: isoflurane, sevoflurane, desflurane, nitrous oxide
• Opioids: fentanyl, alfentanil, morphine, pethidine, remifentanil
• Neuromuscular blockers: rocuronium, vecuronium, cisatracurium, succinylcholine, sugammadex
• Cardiovascular agents: phenylephrine, metaraminol, ephedrine, norepinephrine, epinephrine, metoprolol, esmolol, labetalol, amiodarone, nitroglycerin

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Factors

Aboriginal and Torres Strait Islander peoples have higher prevalence of cardiovascular risk factors, including hypertension, diabetes mellitus, smoking, obesity, and chronic kidney disease. Cardiovascular disease occurs at younger ages and with greater severity compared to non-Indigenous Australians. Rheumatic heart disease remains prevalent in some communities. These factors increase perioperative cardiovascular risk and require careful assessment and optimization. [PMID: various sources on Indigenous cardiovascular health]

Cultural Safety in Communication

Culturally safe communication is essential. Use plain language, avoid medical jargon, and check understanding. Allow sufficient time for questions and discussion. Family and community involvement in decision-making is important and should be welcomed. Respect traditional healing practices and explain their relationship with Western medicine. Address cultural beliefs about illness and surgery that may affect consent and adherence. [PMID: sources on culturally safe communication]

Family and Community Involvement

Family and community are central to Aboriginal and Torres Strait Islander wellbeing. Involve family members in discussions about surgical risks and benefits when appropriate. Consider the role of Elders in decision-making. Be aware that family obligations may influence timing and location of surgery. Aboriginal Health Workers and Liaison Officers can facilitate communication and provide cultural support. [PMID: sources on family involvement in Indigenous healthcare]

Remote/Rural Access to Services

Many Aboriginal and Torres Strait Islander patients live in remote and rural areas with limited access to specialist cardiac services, diagnostic testing, and rehabilitation programs. Pre-operative assessment may require travel to urban centres. Telemedicine and outreach services can improve access. Postoperative follow-up may be challenging; coordinate with local health services and consider longer hospital stay or closer monitoring. Factor in travel time, costs, and social support when planning surgery and discharge. [PMID: sources on remote Indigenous healthcare]

Traditional Medicine Considerations

Some Aboriginal and Torres Strait Islander patients use traditional medicines. These may interact with anaesthetic agents and affect perioperative management. Ask about traditional medicine use in a non-judgmental way. Respect traditional beliefs about illness causation and healing. Collaborate with Aboriginal Health Workers and Liaison Officers to understand and integrate cultural considerations into the care plan. [PMID: sources on traditional medicine use]

Assessment Content

SAQ Practice Question 1 (20 marks)

Clinical Scenario:

A 68-year-old man is scheduled for elective open abdominal aortic aneurysm repair. His medical history includes stable angina (NYHA Class II), hypertension (well-controlled on perindopril and amlodipine), type 2 diabetes mellitus (managed with metformin and empagliflozin), and previous anterior MI 3 years ago (treated with drug-eluting stent). He reports being able to walk 2 blocks on flat ground without chest pain but becomes short of breath walking uphill. His blood pressure is 135/85 mmHg, heart rate 78 bpm, and physical examination is unremarkable. ECG shows sinus rhythm with anterior Q waves. Recent echocardiography shows LV ejection fraction 55% with mild hypokinesis of anterior wall.

Question:

Outline your pre-operative cardiovascular assessment and management plan for this patient, including risk stratification, need for further investigations, medication management, and perioperative anaesthetic considerations.

Model Answer:

Surgical Risk Assessment (2 marks):

• Open abdominal aortic aneurysm repair is high-risk surgery (intraperitoneal, major vascular)
• High risk of perioperative cardiac complications (estimated >5%)

Risk Stratification (4 marks):

• Calculate RCRI:
  • High-risk surgery (1 point)
  • Ischemic heart disease (1 point - previous MI, stable angina)
  • Diabetes requiring insulin? (No - metformin only) (0 points)
  • Cerebrovascular disease? (Not mentioned) (0 points)
  • Congestive heart failure? (No - NYHA II, EF 55%) (0 points)
  • Creatinine >2.0 mg/dL? (Not specified) (0 points)
• RCRI = 2 points → ~6.6% risk of major cardiac events
• Intermediate-to-high risk surgical candidate

Functional Capacity Assessment (3 marks):

• NYHA Class II symptoms (slight limitation, comfortable at rest)
• Exercise tolerance: able to walk 2 blocks on flat ground without symptoms
• Estimated functional capacity: 4-5 METs (moderate capacity)
• METs ≥4: may proceed without further testing
• However, high-risk surgery + known coronary disease justifies further consideration

Pre-operative Testing (4 marks):

• Resting echocardiogram: already done (EF 55%, mild anterior wall hypokinesis) - adequate
• Consider stress testing:
  • Indications: poor or unknown functional capacity (<4 METs) undergoing high-risk surgery
  • This patient has moderate functional capacity (≥4 METs)
  • Stress testing may be considered to assess ischemic burden and guide perioperative management
  • If stress testing performed: dobutamine stress echo or pharmacologic nuclear imaging
  • If results show high ischemic burden, consider cardiology review and possible preoperative revascularization
• Biomarkers: Consider baseline NT-proBNP and high-sensitivity troponin for risk stratification
• Coronary angiography: Not routinely required unless stress testing shows high-risk findings or patient has active cardiac symptoms

Medication Management (3 marks):

• Continue:
  • Perindopril (ACE inhibitor): hold on morning of surgery to reduce intraoperative hypotension risk (optional practice)
  • Amlodipine: continue perioperatively
  • Metformin: continue until day of surgery, withhold postoperatively until renal function confirmed adequate
  • Empagliflozin (SGLT2 inhibitor): CRITICAL - hold 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis; resume when oral intake adequate and no contraindications
• Consider initiating:
  • Beta-blocker: high-risk patient (RCRI 2) with known coronary disease; consider starting at least 1 week before surgery, titrate to heart rate 60-80 bpm; if insufficient time, consider intraoperative and postoperative beta-blockade (esmolol, metoprolol)
  • Statin: already indicated for coronary disease; continue

Perioperative Anaesthetic Considerations (4 marks):

• Invasive arterial pressure monitoring: mandatory for high-risk vascular surgery
• Central venous pressure monitoring: optional, useful for major surgery and vasopressor/inotrope administration
• Advanced haemodynamic monitoring: consider pulse contour analysis (PiCCO, FloTrac) for goal-directed fluid therapy
• Induction: gentle, titrated induction (propofol 1-2 mg/kg + fentanyl 2-5 mcg/kg) to minimize hemodynamic swings
• Maintenance: balanced technique with volatile agent (sevoflurane preferred over isoflurane for coronary disease) + opioid infusion (remifentanil) or intermittent boluses
• Myocardial ischemia monitoring: continuous ST-segment analysis, consider TEE if available
• Temperature management: maintain normothermia (36-37°C)
• Analgesia: multimodal (regional: epidural or TAP block + acetaminophen + NSAID + low-dose opioids)
• Postoperative: high-dependency or ICU care, continuous monitoring, serial troponin measurements at 6-12 and 24 hours to detect MINS

Total: 20 marks

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SAQ Practice Question 2 (20 marks)

Clinical Scenario:

A 55-year-old woman presents for emergency laparotomy for suspected perforated bowel. She is febrile (38.5°C), tachycardic (115 bpm), and hypotensive (85/50 mmHg). She reports a history of dyspnea on exertion for the past 6 months (can walk up one flight of stairs but becomes short of breath). She has no known cardiac disease but takes medication for hypertension. Her creatinine is 180 μmol/L.

Question:

Outline your pre-operative assessment and management of this patient, focusing on cardiovascular considerations, risk stratification, and intraoperative management strategies to optimize outcome.

Model Answer:

Surgical Urgency Assessment (2 marks):

• Emergency laparotomy for perforated bowel: life-threatening condition, surgical urgency highest priority
• Proceed to surgery immediately; pre-operative cardiac testing not appropriate due to time constraints
• Focus on intraoperative management and perioperative monitoring

Pre-operative Cardiovascular Assessment (Limited) (3 marks):

• Rapid assessment of cardiac symptoms:
  • Dyspnea on exertion: can climb one flight of stairs (~4 METs) - suggests NYHA Class II functional capacity
  • No known ischemic heart disease, heart failure, or valvular disease
  • Current tachycardia may be due to sepsis, dehydration, or underlying cardiac dysfunction
• Urgent investigations (if time permits before incision):
  • ECG: assess for ischemia, arrhythmias, hypertrophy, previous infarction
  • Bedside echocardiography (focused cardiac ultrasound): assess ventricular function, volume status, valvular function
  • Arterial blood gas: assess acid-base status, lactate, electrolytes
  • Baseline troponin and NT-proBNP: for comparison postoperatively (may not have results before surgery)
• Blood pressure and heart rate: tachycardic, hypotensive - likely hypovolemic and septic shock

Risk Stratification (3 marks):

• Emergency surgery: high independent risk factor for perioperative complications
• RCRI components:
  • High-risk surgery (intraperitoneal emergency) (1 point)
  • Ischemic heart disease? (Unknown, no reported symptoms) (0 points)
  • Congestive heart failure? (Unknown, dyspnea on exertion may indicate) (0-1 points depending on further assessment)
  • Cerebrovascular disease? (Not mentioned) (0 points)
  • Diabetes requiring insulin? (Not mentioned) (0 points)
  • Preoperative creatinine >2.0 mg/dL (177 μmol/L)? (Yes: 180 μmol/L) (1 point)
• Estimated RCRI: 2-3 points (6.6-11% cardiac risk)
• Emergency surgery in septic patient: actual risk significantly higher

Immediate Pre-operative Optimization (4 marks):

• Fluid resuscitation: balanced crystalloid bolus (500-1000 mL) to restore intravascular volume and improve blood pressure
• Vasopressors: start norepinephrine infusion if hypotension persists despite fluid resuscitation (target MAP >65 mmHg)
• Oxygen: maintain SpO2 >94%
• Antibiotics: administer broad-spectrum antibiotics as soon as possible
• Temperature: maintain normothermia (prevent hypothermia)
• Correction of electrolyte abnormalities: potassium, magnesium, calcium
• Blood products: consider if anemia or coagulopathy present

Intraoperative Monitoring (3 marks):

• Mandatory:
  • Invasive arterial pressure monitoring: essential for beat-to-beat blood pressure and frequent blood sampling
  • Central venous pressure monitoring: for fluid management and vasopressor/inotrope administration
  • Urine output
  • Temperature monitoring
  • Capnography
  • Continuous ECG with ST-segment analysis
• Consider:
  • Cardiac output monitoring (pulse contour analysis, oesophageal Doppler) for goal-directed fluid therapy
  • Focused cardiac ultrasound (TEE if available) to assess ventricular function and volume status
  • Cerebral oximetry (if available)

Intraoperative Anaesthetic Management (5 marks):

• Induction: cautious, titrated induction considering hypovolemia and sepsis
  • Propofol: reduced dose (1-1.5 mg/kg) or alternative induction agent (ketamine 1-2 mg/kg may be beneficial in hypotensive patient)
  • Fentanyl: 2-5 mcg/kg for analgesia and blunting of sympathetic response
  • Rocuronium: 1.2 mg/kg for rapid sequence induction
• Maintenance:
  • Balanced technique with volatile agent (sevoflurane) + opioid infusion (remifentanil) or intermittent boluses
  • Use reduced volatile agent concentration due to sepsis and potential for hypotension
  • Consider TIVA with propofol and remifentanil if concern about volatile-induced hypotension
• Hemodynamic goals:
  • MAP >65 mmHg (individualized based on patient's baseline)
  • Avoid hypotension (<20% below baseline) to prevent organ hypoperfusion
  • Avoid hypertension (may worsen bleeding)
  • Heart rate: 60-100 bpm; tachycardia may be due to sepsis, treat underlying cause
• Fluid management:
  • Goal-directed fluid therapy using stroke volume variation or stroke volume response to fluid challenges
  • Balanced crystalloids for maintenance and resuscitation
  • Consider vasopressors (norepinephrine) early if fluid-unresponsive hypotension
• Analgesia:
  • Multimodal analgesia: acetaminophen, ketamine, low-dose opioids
  • Regional anaesthesia: epidural or TAP block if not contraindicated (caution with coagulopathy from sepsis)
• Temperature: maintain normothermia (36-37°C) with forced-air warming blanket
• Glucose management: target blood glucose 6-10 mmol/L

Total: 20 marks

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Final Clinical Viva Scenario (25 marks)

Clinical Scenario:

You are the anaesthetist for a 72-year-old man undergoing elective right hemicolectomy for colon cancer. His medical history includes stable angina (exertional chest pain relieved by sublingual nitroglycerin), hypertension (treated with losartan and hydrochlorothiazide), and type 2 diabetes (metformin, sitagliptin). He had a myocardial infarction 4 years ago treated with PCI and placement of a drug-eluting stent in the left anterior descending artery. He is currently NYHA Class II (can climb one flight of stairs without chest pain). Medications: aspirin 100 mg daily, metoprolol 50 mg BD, atorvastatin 40 mg nocte, losartan 50 mg daily, hydrochlorothiazide 25 mg daily, metformin 500 mg BD, sitagliptin 100 mg daily. Blood pressure 140/85 mmHg, heart rate 65 bpm, physical examination normal. ECG shows sinus rhythm with inferior Q waves. Recent echocardiogram shows EF 60% with inferior wall hypokinesis.

Viva Dialogue:

Examiner: Good morning. Please summarize this patient's pre-operative cardiovascular risk and outline your management plan.

Candidate: This 72-year-old man has several risk factors for perioperative cardiac complications. Let me systematically assess his risk and develop a management plan.

Examiner: What is his surgical risk and how would you stratify his cardiac risk?

Candidate: Right hemicolectomy is an intermediate-to-high risk procedure (intraperitoneal surgery). For cardiac risk stratification, I'll calculate his Revised Cardiac Risk Index (RCRI). He has:

• High-risk surgery (intraperitoneal): 1 point
• Ischemic heart disease (previous MI, stable angina): 1 point
• Insulin-dependent diabetes? No (metformin only): 0 points
• Cerebrovascular disease? Not mentioned: 0 points
• Congestive heart failure? No (NYHA II, EF 60%): 0 points
• Creatinine >2.0 mg/dL? Not specified: 0 points

RCRI = 2 points, which corresponds to approximately 6.6% risk of major cardiac events. This places him in an intermediate-to-high risk category.

Examiner: What about his functional capacity and need for further cardiac testing?

Candidate: He is NYHA Class II, reporting ability to climb one flight of stairs without chest pain. This corresponds to approximately 4-5 METs of functional capacity. According to ACC/AHA guidelines, patients with adequate functional capacity (≥4 METs) can generally proceed to surgery without further testing unless additional risk factors are present.

However, given his known coronary artery disease with previous MI and stent placement, I would consider additional factors:

• The drug-eluting stent was placed 4 years ago, which is >12 months. Current guidelines recommend dual antiplatelet therapy for at least 6-12 months after drug-eluting stent placement, then lifelong aspirin.
• He is currently on aspirin 100 mg daily, which is appropriate. Metoprolol and atorvastatin indicate he is receiving guideline-directed medical therapy for ischemic heart disease.

I would check:

1. When was the stent placed? (4 years ago is >12 months, so aspirin monotherapy is adequate)
2. Is his angina well-controlled? (Yes, NYHA II)
3. Has he had recent cardiac evaluation? (Has echocardiogram showing EF 60%)

Given that he has adequate functional capacity and is stable on medical therapy, I would not require routine pre-operative stress testing. However, I would obtain baseline cardiac biomarkers (NT-proBNP and high-sensitivity troponin) for risk stratification and postoperative comparison.

Examiner: How would you manage his medications in the perioperative period?

Candidate: Let me go through each medication:

Aspirin 100 mg daily: Continue perioperatively. For patients with coronary stents, continuing aspirin reduces cardiovascular risk and generally does not increase surgical bleeding significantly. The small increased risk of bleeding is outweighed by the cardiovascular benefit.

Metoprolol 50 mg BD: Continue. He is on chronic beta-blocker therapy for coronary disease. Abrupt withdrawal can cause rebound tachycardia and hypertension, increasing myocardial oxygen demand. Continue his regular dose through the perioperative period. If he was not on a beta-blocker, I would consider initiating one preoperatively given his RCRI of 2, but he's already established on therapy.

Atorvastatin 40 mg nocte: Continue. Statins reduce perioperative cardiovascular events. Continue his regular dose. If he wasn't on a statin, I would initiate one preoperatively given his coronary disease.

Losartan 50 mg daily: Hold on the morning of surgery. ACE inhibitors and ARBs can cause significant intraoperative hypotension under anaesthesia. There's variability in practice - some continue, some hold. Holding reduces risk of refractory hypotension. Resume postoperatively when hemodynamically stable.

Hydrochlorothiazide 25 mg daily: Continue. This is a diuretic, but the dose is moderate. Continue preoperatively, but be aware that he may be relatively volume-depleted intraoperatively. Monitor urine output and fluid balance.

Metformin 500 mg BD: Continue until the morning of surgery, then hold postoperatively. Hold for 24-48 hours after surgery until renal function is confirmed to be adequate (creatinine stable). Resume when oral intake is adequate and no contraindications (e.g., contrast-induced nephropathy, hemodynamic instability).

Sitagliptin 100 mg daily: Hold preoperatively. DPP-4 inhibitors generally have fewer issues than SGLT2 inhibitors regarding ketoacidosis, but it's reasonable to hold on the morning of surgery and resume when oral intake is adequate.

Examiner: What anaesthetic technique and monitoring would you use for this patient?

Candidate: For monitoring, given his RCRI of 2 and known coronary artery disease:

Standard ASA monitoring: ECG, NIBP, SpO2, capnography, temperature

Invasive arterial pressure monitoring: I would place an arterial line pre-induction for beat-to-beat blood pressure monitoring and frequent arterial blood gas sampling. This allows rapid detection and treatment of hypotension or hypertension, which could compromise myocardial oxygen balance.

Central venous pressure monitoring: Consider CVP for major abdominal surgery, especially if there are concerns about fluid status or need for vasopressor/inotrope administration. However, CVP has limitations in predicting fluid responsiveness.

Advanced hemodynamic monitoring: Consider pulse contour analysis (PiCCO or FloTrac) for goal-directed fluid therapy and cardiac output monitoring. This helps optimize fluid administration and detect changes in cardiac function.

For anaesthetic technique:

Premedication: Avoid heavy premedication that could cause respiratory depression. Small dose of midazolam (1-2 mg) for anxiolysis if appropriate.

Induction: Gentle, titrated induction to minimize hemodynamic fluctuations.

• Propofol: 1.5-2 mg/kg, titrated slowly while monitoring hemodynamics
• Fentanyl: 2-5 mcg/kg for analgesia and blunting of sympathetic response to laryngoscopy
• Rocuronium: 0.6 mg/kg for neuromuscular blockade

Alternatively, consider etomidate 0.2-0.3 mg/kg if concerned about propofol-induced hypotension, though etomidate has its own concerns about adrenal suppression.

Maintenance: Balanced anaesthetic technique

• Volatile agent: Sevoflurane (preferred over isoflurane in patients with coronary disease due to lower risk of coronary steal phenomenon). Maintain at 0.7-1.0 MAC
• Opioids: Intermittent fentanyl boluses (50-100 mcg) or remifentanil infusion (0.05-0.2 mcg/kg/min) for analgesia and hemodynamic stability
• Neuromuscular blockade: Rocuronium with quantitative monitoring and reversal with sugammadex at end of surgery

Emergence: Smooth emergence with adequate analgesia to prevent hypertension and tachycardia.

Examiner: What specific strategies would you use to prevent myocardial ischemia during surgery?

Candidate: Myocardial ischemia occurs when myocardial oxygen demand exceeds supply. Strategies to prevent ischemia focus on reducing demand and optimizing supply:

Reduce myocardial oxygen demand:

• Maintain heart rate 60-80 bpm: Tachycardia increases myocardial oxygen consumption and reduces diastolic filling time. Use beta-blockers (esmolol bolus or metoprolol) if HR >80. Ensure adequate depth of anaesthesia and analgesia.
• Maintain blood pressure within 20% of baseline: Hypertension increases afterload and oxygen demand; hypotension reduces coronary perfusion pressure. Use vasopressors (phenylephrine for hypotension with tachycardia, metaraminol for hypotension with normal/bradycardia). Treat hypertension with deepening anaesthesia, analgesia, or antihypertensives (labetalol).
• Avoid anemia: Hemoglobin <80 g/L reduces oxygen-carrying capacity. Consider transfusion if anemia present and symptomatic or if ongoing bleeding.
• Avoid hyperthermia: Fever increases metabolic rate and oxygen consumption. Maintain normothermia.

Optimize myocardial oxygen supply:

• Maintain adequate coronary perfusion pressure: Diastolic pressure >60 mmHg is crucial for coronary perfusion. Treat hypotension promptly.
• Maintain adequate oxygenation: SpO2 >94%. Ensure adequate ventilation.
• Optimize hemoglobin: Transfuse if hemoglobin <80 g/L, consider earlier in patients with known coronary disease (some guidelines suggest >90-100 g/L).
• Avoid coronary vasoconstriction: Sevoflurane is preferred over isoflurane in coronary disease. Avoid hyperventilation (causes cerebral vasoconstriction, may affect coronary tone). Treat shivering (increases oxygen demand).
• Continuous ST-segment monitoring: Detect ischemia early (ST depression or elevation ≥1 mm). Early detection allows prompt treatment (deepen anaesthesia, increase blood pressure, treat tachycardia, administer nitrates, involve cardiology if persistent).

Additional strategies:

• Goal-directed fluid therapy: Avoid both hypovolemia (reduces preload and cardiac output) and hypervolemia (increases afterload and risk of pulmonary edema in patients with cardiac dysfunction).
• Multimodal analgesia: Reduce sympathetic activation from pain. Use regional anaesthesia (epidural or TAP block), acetaminophen, NSAIDs (if not contraindicated), and low-dose opioids.
• Maintain normothermia: Prevent shivering and increased oxygen consumption.

Examiner: How would you manage this patient postoperatively?

Candidate: Postoperatively, I would manage him in a high-dependency unit for at least 24 hours given his cardiac risk factors.

Monitoring:

• Continuous ECG monitoring for arrhythmias and ischemia
• Continuous blood pressure monitoring (invasive line if still in place)
• Frequent vital signs: BP, HR, RR, SpO2, temperature, urine output
• Serial cardiac biomarkers: High-sensitivity troponin at 6-12 hours postoperatively and at 24 hours. This screens for myocardial injury after noncardiac surgery (MINS), which occurs in up to 20% of high-risk patients and is associated with increased mortality.
• Consider NT-proBNP if elevated baseline

Analgesia:

• Multimodal analgesia: Epidural (if used intraoperatively) or TAP block + acetaminophen 1g 6-hourly + NSAID (e.g., ketorolac 10 mg 6-hourly, not contraindicated) + low-dose opioids
• Adequate analgesia reduces sympathetic activation and myocardial oxygen demand

Hemodynamic goals:

• Maintain blood pressure within 20% of baseline
• Heart rate 60-80 bpm
• Treat hypotension with fluids (if hypovolemic) or vasopressors (norepinephrine)
• Treat hypertension with analgesia, antihypertensives (beta-blockers)

Medications:

• Continue aspirin 100 mg daily
• Continue metoprolol (regular dose)
• Continue atorvastatin (regular dose)
• Restart losartan when hemodynamically stable (usually 24-48 hours postoperatively)
• Restart hydrochlorothiazide
• Restart metformin when renal function confirmed adequate (creatinine stable, urine output adequate) and patient tolerating oral intake
• Restart sitagliptin when tolerating oral intake

Fluid management:

• Goal-directed fluid therapy based on stroke volume variation or clinical parameters
• Avoid fluid overload (risk of pulmonary edema in patients with cardiac dysfunction)

Early mobilization:

• Encourage early ambulation when hemodynamically stable and pain controlled
• Reduces risk of venous thromboembolism, pneumonia, and atelectasis

Discharge planning:

• Arrange cardiology follow-up if any concerns about cardiac status
• Patient education about warning signs of cardiac complications (chest pain, shortness of breath, palpitations)
• Medication reconciliation and education

Examiner: What if intraoperative ST depression develops? How would you manage that?

Candidate: ST depression ≥1 mm in two or more contiguous leads indicates myocardial ischemia. I would systematically address this:

Immediate actions:

1. Confirm the finding: Check ECG leads, rule out artifact
2. Assess hemodynamics: Blood pressure, heart rate, cardiac output if monitored
3. Assess surgical stimulation: Is there a surgical stimulus causing sympathetic activation?
4. Check oxygenation and ventilation: SpO2, EtCO2, arterial blood gas
5. Check depth of anaesthesia: Is the patient too light?

Specific interventions:

• Treat tachycardia: Deepen anaesthesia, administer analgesic (fentanyl 50-100 mcg), or give beta-blocker (esmolol 25-50 mg bolus, or metoprolol 1-5 mg)
• Treat hypertension: Deepen anaesthesia, administer labetalol 5-10 mg IV, or nitroglycerin infusion (start at 0.5 mcg/kg/min)
• Treat hypotension: Fluid bolus 250-500 mL crystalloid, vasopressor (phenylephrine 50-100 mcg or metaraminol 0.5-1 mg)
• Ensure adequate oxygenation: Increase FiO2 to 100%, check for airway or ventilation problems
• Consider diagnostic studies: TEE if available to assess wall motion abnormalities and ventricular function
• Consider cardiology consultation if ischemia persists despite treatment

Persistent ischemia despite treatment:

• Consider reducing surgical stimulus if possible
• Consider increasing MAP to ensure adequate coronary perfusion pressure (>65 mmHg or higher if baseline hypertension)
• Consider nitrates (nitroglycerin) for coronary vasodilation and preload reduction
• Consider inotropes (dobutamine) if cardiac dysfunction is present
• Emergency cardiology consultation and possible intraoperative intervention

Postoperative management if intraoperative ischemia occurred:

• Continue ICU/HDU care for extended monitoring
• Serial ECGs and troponin measurements (every 6-8 hours for 24 hours)
• Urgent cardiology consultation
• Consider early coronary angiography if ischemia was significant or persistent
• Optimize anti-ischemic therapy (beta-blocker, nitrates, statins, antiplatelet agents)

Examiner: How would your approach differ if this was an Aboriginal or Torres Strait Islander patient?

Candidate: For an Aboriginal or Torres Strait Islander patient, I would consider additional factors:

Epidemiological considerations:

• Higher prevalence of cardiovascular risk factors (hypertension, diabetes, smoking, CKD) often at younger ages
• Cardiovascular disease occurs with greater severity and earlier onset
• Higher risk of rheumatic heart disease in some communities

Cultural safety:

• Use plain language, avoid medical jargon, check understanding
• Allow sufficient time for questions and discussion
• Respect family and community involvement in decision-making
• Involve Aboriginal Health Workers and Liaison Officers to facilitate communication and provide cultural support

Social determinants:

• Consider access to follow-up care, especially if patient lives in remote community
• Consider travel logistics for pre-operative testing, surgery, and postoperative care
• Consider family and community responsibilities that may affect timing of surgery or length of stay

Traditional medicine:

• Ask about traditional medicine use in a non-judgmental way
• Respect traditional beliefs about illness causation and healing
• Consider potential interactions between traditional medicines and anaesthetic agents

Health service factors:

• Coordinate with local Aboriginal Medical Service or Community Health Centre
• Ensure culturally safe communication and care processes
• Consider need for longer hospital stay or closer monitoring if follow-up in remote location is challenging

Medication management:

• Consider adherence barriers (cost, access, understanding)
• Ensure clear medication instructions and education
• Involve family in medication education and planning

The core clinical principles remain the same, but cultural safety and community context are essential considerations to ensure equitable outcomes.

Total: 25 marks

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Final Medical Viva Scenario (25 marks)

Medical Viva Question:

Discuss the role of cardiac biomarkers (NT-proBNP and high-sensitivity troponin) in pre-operative cardiovascular risk assessment and postoperative management of patients undergoing noncardiac surgery.

Viva Dialogue:

Examiner: Good morning. Let's discuss cardiac biomarkers in perioperative medicine. What are the main cardiac biomarkers used in the perioperative period and what do they measure?

Candidate: The main cardiac biomarkers used in the perioperative period are:

Cardiac troponins (cTnI and cTnT):

• These are regulatory proteins found in cardiac myocytes
• Troponin I inhibits actin-myosin interaction; troponin T binds tropomyosin
• Cardiac-specific isoforms (cTnI, cTnT) are released when cardiac myocytes are injured
• High-sensitivity troponin assays can detect very low levels of troponin, allowing earlier detection of myocardial injury
• Troponin elevation indicates myocardial injury due to any cause: ischemia (type 1 MI), supply-demand mismatch (type 2 MI), or other causes (sepsis, pulmonary embolism, renal failure)

Natriuretic peptides:

• B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP)
• BNP is released primarily from ventricular myocytes in response to increased wall stress and volume overload
• NT-proBNP is the inactive N-terminal fragment cleaved from proBNP; it has a longer half-life than BNP (60-120 minutes vs 20 minutes)
• Elevated levels indicate ventricular dysfunction (systolic or diastolic) or pressure overload
• Used for diagnosing and monitoring heart failure

Examiner: What is the evidence for using pre-operative NT-proBNP or BNP for cardiac risk stratification?

Candidate: Several studies and meta-analyses have demonstrated that pre-operative natriuretic peptide measurement is a powerful predictor of perioperative cardiac events.

Key evidence includes:

• Meta-analyses show that elevated pre-operative NT-proBNP or BNP is associated with 2-4 times increased risk of 30-day mortality and major adverse cardiac events after noncardiac surgery
• The predictive value is independent of clinical risk scores like RCRI
• Elevated pre-operative NT-proBNP (>300 ng/L) is associated with increased risk of myocardial injury, heart failure, arrhythmias, and death
• The strongest predictive value is in patients undergoing vascular or major abdominal surgery

Mechanisms:

• Elevated NT-proBNP indicates subclinical ventricular dysfunction or increased myocardial stress
• Patients with elevated levels have reduced cardiac reserve and are less able to tolerate perioperative hemodynamic stress
• May identify patients with undiagnosed cardiac disease that would benefit from optimization

Clinical utility:

• Pre-operative NT-proBNP measurement can help refine risk stratification, especially in intermediate-risk patients
• May identify patients who would benefit from more intensive monitoring, optimization of cardiac therapy, or pre-operative cardiology review
• The 2022 ESC Guidelines recommend measuring pre-operative NT-proBNP in patients >65 years or with known cardiovascular disease undergoing intermediate-to-high-risk surgery

Limitations:

• Elevated NT-proBNP is not specific to cardiac disease; can be elevated in renal failure, sepsis, pulmonary embolism
• A normal NT-proBNP does not completely rule out cardiac risk (negative predictive value high but not absolute)
• Cost-effectiveness of routine pre-operative NT-proBNP measurement is still debated

Examiner: What about postoperative troponin measurement? What is myocardial injury after noncardiac surgery (MINS)?

Candidate: Myocardial injury after noncardiac surgery (MINS) is a relatively recently recognized clinical entity.

Definition:

• MINS is defined as myocardial injury due to ischemia within 30 days after noncardiac surgery, manifested by:
  1. Elevated troponin with ischemic features (ST-segment changes, new Q waves, imaging evidence of new loss of viable myocardium, or coronary thrombus) OR
  2. Elevated troponin judged as due to ischemia without a non-ischemic cause, even without ischemic features

Epidemiology:

• Occurs in approximately 8-20% of patients undergoing major noncardiac surgery
• More common in high-risk patients (vascular surgery, major abdominal surgery, cardiac risk factors)
• The majority of MINS cases (up to 80%) are asymptomatic without ischemic symptoms

Pathophysiology:

• Most MINS cases are type 2 myocardial infarction (supply-demand mismatch) rather than plaque rupture (type 1)
• Supply-demand mismatch can be caused by: tachycardia, hypotension, hypertension, anemia, hypoxia, pain, fever
• Inflammation and hypercoagulability of surgery may also contribute
• Some cases may be due to plaque rupture or thrombosis (type 1 MI)

Prognostic significance:

• MINS is strongly associated with increased 30-day mortality (up to 10% mortality in patients with MINS)
• Associated with increased risk of heart failure, arrhythmias, stroke, and long-term mortality
• Even small troponin elevations (just above the 99th percentile URL) are associated with worse outcomes
• The higher the peak troponin, the worse the prognosis

Detection:

• Routine postoperative troponin monitoring in high-risk patients is recommended
• Measure troponin at 6-12 hours postoperatively and again at 24-48 hours
• High-sensitivity troponin assays allow earlier detection and more sensitive diagnosis of MINS

Management:

• The VISION trial and other studies have investigated optimal management strategies
• Current recommendations include:
  1. Cardiology consultation
  2. Initiate or continue low-dose aspirin unless contraindicated
  3. Consider statin therapy if not already prescribed
  4. Consider beta-blocker therapy, especially if tachycardic or hypertensive
  5. Avoid antiplatelet therapy other than aspirin unless there is clear indication for dual antiplatelet therapy
  6. Avoid routine coronary revascularization in asymptomatic MINS (similar to medical management strategy for stable coronary disease)
  7. Optimize hemodynamics, oxygenation, hematocrit, and other factors contributing to supply-demand mismatch

Evidence from trials:

• The VISION study (PMID 22610085, 23343071) was a large prospective cohort study that established the prognostic importance of MINS
• MANAGE trial (PMID 29973655) investigated anticoagulation with dabigatran in MINS but found increased bleeding without clear benefit
• Current evidence supports medical management rather than routine revascularization for most MINS patients

Examiner: How do you integrate cardiac biomarkers into clinical practice? Give me a practical approach.

Candidate: A practical approach to using cardiac biomarkers in perioperative care:

Pre-operative assessment:

Indications for pre-operative NT-proBNP measurement:

• Patients >65 years undergoing intermediate-to-high-risk surgery
• Patients of any age with known cardiovascular disease undergoing intermediate-to-high-risk surgery
• Intermediate-risk patients (RCRI 1-2) where biomarker results would change management

Interpretation of pre-operative NT-proBNP:

• Normal (<300 ng/L): Low cardiac risk, can generally proceed with surgery without further cardiac testing
• Elevated (>300 ng/L): Increased cardiac risk
  • If RCRI low (0-1): Consider enhanced monitoring, optimization of cardiac therapy
  • If RCRI intermediate (2): Consider pre-operative cardiology review, optimization, possibly stress testing
  • If RCRI high (≥3): Cardiology review indicated, consider pre-operative optimization, possible postponement for further investigation

Clinical decision-making based on NT-proBNP:

• May help decide whether pre-operative stress testing or cardiology consultation is indicated
• May influence level of postoperative monitoring (ward vs HDU vs ICU)
• May influence perioperative medical therapy (initiate or optimize beta-blockers, statins)

Postoperative monitoring:

Indications for postoperative troponin monitoring:

• High-risk surgery (vascular, major abdominal, thoracic)
• RCRI ≥2
• Known coronary artery disease, heart failure, cerebrovascular disease
• Perioperative hemodynamic instability (hypotension, tachycardia)
• Age >65 years

Timing of postoperative troponin measurement:

• Measure at 6-12 hours postoperatively (or in recovery room if concerns)
• Repeat at 24-48 hours postoperatively
• Earlier if clinical concern (hemodynamic instability, ECG changes, arrhythmias)

Interpretation of postoperative troponin:

• Normal: Reassuring, no evidence of MINS
• Elevated above 99th percentile URL: Diagnosis of myocardial injury
  • Consider ischemic vs non-ischemic cause
  • Look for ECG changes, symptoms, hemodynamic instability
  • Review perioperative events (hypotension, tachycardia, anemia, hypoxia)
  • If troponin elevation >5x URL with ECG changes or imaging evidence: definite myocardial infarction
  • If troponin elevation >5x URL without ECG changes: probable myocardial injury (type 2 MI likely)
  • If troponin elevation 1-5x URL: myocardial injury (may be MINS or non-ischemic)

Management of elevated postoperative troponin:

1. Cardiology consultation
2. Investigate: ECG, echocardiogram, consider coronary angiography if suspicion of acute coronary syndrome
3. Treat underlying causes: hypotension, tachycardia, anemia, hypoxia, pain
4. Initiate or continue:
   • Low-dose aspirin (if not contraindicated)
   • Statin therapy
   • Beta-blocker therapy (especially if tachycardic/hypertensive)
5. Level of care: ICU or HDU for at least 24-48 hours with continuous monitoring
6. Avoid routine dual antiplatelet therapy or anticoagulation unless clear indication

Practical considerations:

• High-sensitivity troponin assays are preferred for early detection
• Establish reference ranges specific to the laboratory
• Consider renal function when interpreting troponin (troponin clearance is renal-dependent, though hs-troponin assays less affected)
• Document baseline troponin in patients with known chronic troponin elevation (e.g., renal failure, heart failure)
• Ensure systems for timely communication of troponin results to clinical team

Example clinical scenario: 70-year-old man with known CAD (previous MI, stent 3 years ago) undergoing hemicolectomy for colon cancer.

• Pre-operative: NT-proBNP measured: 450 ng/L (elevated). RCRI = 2 (high-risk surgery, CAD).
• Interpretation: Elevated NT-proBNP in intermediate-risk patient indicates increased cardiac risk. Consider cardiology review, ensure optimization of cardiac therapy. Plan for enhanced postoperative monitoring (HDU/ICU).
• Postoperative: Troponin at 12 hours: 35 ng/L (URL 14 ng/L, elevated >2x URL). Patient asymptomatic, ECG normal.
• Interpretation: MINS. Cardiology consultation initiated. Aspirin 100 mg daily started. Continue statin, beta-blocker. Monitor in HDU. Repeat troponin at 24 hours: 40 ng/L (slightly increased). Continue monitoring.

Examiner: What are the controversies or areas of uncertainty in using cardiac biomarkers perioperatively?

Candidate: Several controversies and areas of uncertainty exist:

Pre-operative NT-proBNP:

• Cost-effectiveness: Routine pre-operative NT-proBNP measurement increases healthcare costs. The cost-benefit ratio is debated, especially in low-risk patients.
• Actionability: Elevated NT-proBNP identifies risk but doesn't always lead to specific interventions. How should management change based on the result?
• Risk stratification: NT-proBNP adds prognostic information beyond clinical risk scores, but guidelines differ on when to measure it and how to act on the results.
• Thresholds: The optimal cut-off for elevated NT-proBNP varies between studies and populations (generally >300 ng/L, but age- and sex-specific cut-offs exist).
• Interaction with other biomarkers: Should we use a multi-biomarker approach (NT-proBNP + troponin + other biomarkers)?

Postoperative troponin and MINS:

• Optimal monitoring frequency: Should we measure troponin routinely in all patients >65 years, or only in high-risk patients? The 2022 ESC Guidelines recommend routine monitoring in patients with clinical risk factors or undergoing high-risk surgery.
• Asymptomatic MINS management: The optimal management of asymptomatic MINS is uncertain. The MANAGE trial did not show clear benefit from anticoagulation. Should we initiate antiplatelet therapy, beta-blockers, statins in all MINS patients, or only selected high-risk patients?
• Long-term outcomes: Does treating MINS improve long-term outcomes, or is it simply a marker of poor prognosis? Randomized trials are limited.
• Diagnostic criteria: The definition of MINS has evolved and continues to be refined. What is the optimal threshold for troponin elevation? How should we distinguish ischemic vs non-ischemic causes?

Implementation barriers:

• System issues: Lack of standardized protocols for biomarker measurement, communication of results, and follow-up.
• Education: Need for education of surgeons, anaesthetists, and other perioperative clinicians about the significance of biomarker elevations.
• Resources: May not be available in all centres, especially smaller hospitals or low-resource settings.

Special populations:

• Chronic kidney disease: Baseline troponin elevation and NT-proBNP elevation are common. What are the appropriate reference ranges and thresholds?
• Heart failure: Chronic troponin and NT-proBNP elevation. How to distinguish acute changes from chronic elevation?
• Frailty and elderly: Higher baseline biomarkers and higher risk. How should thresholds be adjusted?

Research gaps:

• Randomized controlled trials are needed to determine if interventions based on biomarker results improve outcomes.
• Studies are needed on the cost-effectiveness of routine biomarker measurement.
• Optimal treatment strategies for MINS need further investigation.

Despite these controversies, the evidence strongly supports that cardiac biomarkers provide important prognostic information and can help identify high-risk patients who benefit from enhanced monitoring and optimization of medical therapy. Integration into clinical practice is increasing, though guidelines continue to evolve as evidence accumulates.

Examiner: Finally, how do cardiac biomarkers relate to the concept of "perioperative myocardial infarction" vs "myocardial injury after noncardiac surgery"?

Candidate: This is an important distinction. Traditionally, we focused on diagnosing "perioperative myocardial infarction" using the Universal Definition of Myocardial Infarction. However, this approach missed many patients who had myocardial injury without meeting the full criteria for MI.

Perioperative myocardial infarction (PMI):

• Defined by Universal Definition of MI criteria:
  • Detection of rise/fall in troponin with at least one value above the 99th percentile URL AND
  • At least one of the following:
    • Symptoms of myocardial ischemia
    • New ischemic ECG changes (ST elevation/depression, new LBBB)
    • Development of pathological Q waves
    • Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
    • Identification of coronary thrombus by angiography or autopsy
• Focuses on diagnosing myocardial infarction (type 1 MI or type 2 MI)

Myocardial injury after noncardiac surgery (MINS):

• Broader concept that includes PMI but also includes:
  • Troponin elevation without overt ischemic features (symptoms, ECG changes)
  • Troponin elevation due to supply-demand mismatch without obvious plaque rupture
• Recognizes that even asymptomatic troponin elevations are prognostically important
• The majority of MINS cases are asymptomatic without chest pain or ECG changes

Key differences:

1. PMI requires evidence of ischemia (symptoms or ECG changes); MINS does not.
2. PMI is a subset of MINS.
3. MINS is more common than PMI (up to 80% of MINS patients are asymptomatic).
4. PMI criteria may miss patients with significant troponin elevation but no overt ischemic features.
5. Both PMI and MINS are associated with increased mortality, but MINS identifies a larger high-risk population.

Clinical implications:

• Using PMI criteria alone would miss many high-risk patients who need intervention.
• MINS broadens the definition to include all patients with troponin elevation due to ischemia.
• Routine troponin monitoring (not just monitoring symptomatic patients) is essential to detect MINS.
• Management of MINS may be similar to PMI (cardiology consultation, aspirin, statin, beta-blocker), but evidence is still evolving.

Evolution of terminology:

• The VISION study introduced the concept of MINS.
• The Fourth Universal Definition of MI (2018) now includes type 2 MI (supply-demand mismatch) and recognizes that perioperative MI is often type 2 rather than type 1.
• Current guidelines increasingly use the term MINS to emphasize the importance of detecting and treating myocardial injury even in the absence of classic MI criteria.

Summary: Cardiac biomarkers, particularly high-sensitivity troponin, are essential tools for detecting myocardial injury after noncardiac surgery. The concept of MINS recognizes that significant myocardial injury occurs perioperatively even in the absence of classic MI features. Routine troponin monitoring in high-risk patients allows early detection of MINS, which is associated with increased mortality and may benefit from targeted interventions. Pre-operative NT-proBNP measurement can identify patients at increased risk and guide perioperative management. However, controversies remain regarding optimal implementation, thresholds, and management strategies.

Total: 25 marks

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References

1. Fleisher LA, Fleischmann KE, Auerbach AD, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: executive summary. Circulation. 2014;130(24):e210-e241. PMID: 25085415

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