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Anaesthesia for Hypertension and IHD - Complete Practical Viva Guide

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PART 1: HYPERTENSION AND ANAESTHESIA

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1. PATHOPHYSIOLOGY RELEVANT TO ANAESTHESIA

• Left ventricular hypertrophy (LVH) - reduces ventricular compliance (diastolic dysfunction); requires higher filling pressures
• Altered cerebral autoregulation - the curve is shifted rightward; higher MAPs needed to maintain cerebral perfusion in long-standing disease
• Accelerated atherosclerosis - increases risk of CAD, stroke, renal impairment
• Volume depletion - chronic diuretic use and natriuresis lead to relative hypovolaemia
• Increased vascular reactivity - exaggerated pressor response to laryngoscopy and surgical stimulation

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2. PREOPERATIVE ASSESSMENT

History

• Duration and severity of hypertension
• Current medications (antihypertensives) - do NOT stop most of them (see below)
• End-organ damage: cardiac (LVH, CCF, IHD), renal (CKD), cerebrovascular (stroke/TIA), retinal
• Concurrent DM, obesity, smoking

Should surgery be cancelled for uncontrolled hypertension?

• Stage 1-2 hypertension (DBP <110 mmHg): does NOT need to be delayed - no proven increase in perioperative complications from elective surgery
• Stage 3 / severe (DBP >110 mmHg, SBP >180 mmHg): surgery should be postponed for elective procedures to achieve better control
• Emergency surgery: proceed regardless, with careful intraoperative monitoring and blood pressure management
• Key principle: the anaesthesiologist must weigh risks of delaying surgery vs. risks of proceeding

JNC Classification for reference:

Physical Examination

• Ophthalmoscopy: retinal changes (AV nicking, flame haemorrhages, papilloedema) reflect severity and end-organ damage
• S4 gallop: indicates LVH
• Pulmonary rales + S3: late sign - suggests CCF
• Carotid bruits: may indicate atherosclerotic disease affecting coronary circulation
• BP in both arms and supine/standing (orthostatic changes = volume depletion or sympatholytic drugs)

Investigations

• ECG: LVH voltage criteria, ST-T changes, arrhythmias
• CXR: cardiomegaly, pulmonary congestion
• Echocardiogram: if LVH suspected - assess EF, wall thickness, diastolic function
• Serum creatinine: renal function
• Electrolytes: K+ (especially if on diuretics or ACE inhibitors)
  • Mild hypokalemia (K+ 3.0-3.5): does not need replacement unless symptomatic or on digoxin
  • Check Mg2+ - hypomagnesaemia causes perioperative arrhythmias
  • ACE inhibitors / K+-sparing diuretics → hyperkalemia

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3. ANTIHYPERTENSIVE DRUGS - ANAESTHETIC IMPLICATIONS

• Thiazides: hypokalemia, hyperglycemia, hyperuricemia, hyponatremia
• Loop diuretics: hypokalemia, hypomagnesaemia, metabolic alkalosis
• Beta-blockers: bradycardia, conduction block, myocardial depression, bronchospasm, sedation, fatigue, masks hypoglycemia
• CCBs (verapamil/diltiazem): cardiac depression, bradycardia, enhanced neuromuscular blockade
• ACE inhibitors: cough, angioedema, renal dysfunction, hyperkalemia - ACE inhibitor-induced angioedema can require emergency airway management
• Clonidine: sedation, decreased MAC, rebound hypertension on sudden withdrawal

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4. PREMEDICATION

• Anxiolysis with midazolam resolves "white coat" hypertension in many patients
• Continue all antihypertensives on the morning of surgery with a sip of water
• Pre-operative carbohydrate drink (night before + morning) can promote haemodynamic stability post-induction

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5. INTRAOPERATIVE MANAGEMENT

Goals

• Maintain BP within 20% of preoperative baseline (this is the key target)
• Avoid tachycardia - increases myocardial oxygen demand
• In long-standing hypertension: higher MAPs needed (autoregulation curve shifted right)
• Prevent the bimodal response: hypotension at induction → hypertension at laryngoscopy

Monitoring

• Standard monitoring for most patients (NIBP, ECG with ST analysis, SpO2)
• Invasive arterial line: indicated for
  • Wide BP swings
  • Major surgery with large fluid shifts
  • Severe/poorly controlled hypertension
• ECG monitoring: focus on lead V5 (detects 75% of ischemia) + lead II
• Urinary catheter: if renal impairment + surgery >2 hours
• Avoid excessive IV fluids in LVH (reduced ventricular compliance → pulmonary oedema)

Induction - the most critical phase

Key fact: Hypertensive patients show accentuated hypotension at induction followed by exaggerated hypertension at laryngoscopy/intubation

• Many antihypertensives and general anaesthetics are vasodilators, cardiac depressants, or both
• Many patients are relatively volume-depleted preoperatively

1. Deepen anaesthesia with volatile agent before intubation
2. Opioid bolus prior to laryngoscopy:
   • Fentanyl 2.5-5 mcg/kg
   • Alfentanil 15-25 mcg/kg
   • Sufentanil 0.5-1.0 mcg/kg
   • Remifentanil infusion
3. IV Lignocaine 1.5-2 mg/kg (IV or intratracheal)
4. Beta-blocker (esmolol 0.5-1 mg/kg IV or labetalol)
5. Vasodilators: nitroprusside, nitroglycerin bolus
6. Clonidine premedication
7. Use video laryngoscopy - less stimulating than direct laryngoscopy

• All agents (propofol, thiopentone, etomidate) can be used
• Ketamine - generally avoided as it raises BP (sympathomimetic); may be used cautiously in emergencies
• Propofol - most common; attenuates pressor response well

Maintenance

• Any volatile agent acceptable (isoflurane, sevoflurane, desflurane)
• Avoid N2O in patients with pulmonary hypertension
• TIVA is also acceptable (Class IIa recommendation, Level A)

Intraoperative Hypertension - Management

1. Deepen anaesthesia
2. Ensure adequate analgesia
3. IV labetalol (5-20 mg boluses)
4. IV hydralazine (5-10 mg, slow onset)
5. IV esmolol (short-acting, titratable)
6. IV sodium nitroprusside (hypertensive emergency - immediate but transient)
7. IV nitroglycerin (especially if ischemia suspected)
8. IV nicardipine (calcium channel blocker infusion)

Intraoperative Hypotension - Management

• IV fluid bolus (assess volume status)
• Reduce volatile agent
• Vasopressors: phenylephrine (pure alpha, does not increase HR), noradrenaline
• Ephedrine (if bradycardic)

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6. POSTOPERATIVE CONSIDERATIONS

• Poorly controlled preoperative hypertension → severe postoperative hypertension (common after carotid endarterectomy due to surgical denervation of carotid sinus baroreceptors)
• Pain is a major trigger of postoperative hypertension - treat aggressively
• Resume all antihypertensives as early as possible post-surgery (oral or IV equivalent)
• Regional anaesthesia is associated with better BP stability in the postoperative period

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PART 2: ISCHAEMIC HEART DISEASE (IHD) AND ANAESTHESIA

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1. WHY IHD MATTERS PERIOPERATIVELY

• Sympathetic activation → tachycardia + hypertension → increased O2 demand
• Hypercoagulable state → plaque rupture, coronary thrombosis
• Fluid shifts → volume overload or hypovolaemia
• Pain, hypoxia, anaemia → decreased O2 supply

• Supply: diastolic BP (coronary perfusion pressure), HR (coronary filling time), Hb, SpO2, coronary vasomotor tone
• Demand: HR (most important), wall tension (preload + afterload), contractility

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2. PREOPERATIVE RISK ASSESSMENT

RCRI (Revised Cardiac Risk Index) - Lee Index

1. High-risk surgery (intraperitoneal, intrathoracic, suprainguinal vascular)
2. History of ischemic heart disease
3. History of heart failure
4. History of cerebrovascular disease
5. Insulin-dependent diabetes mellitus
6. Preoperative creatinine >2 mg/dL

ACC/AHA Active Cardiac Conditions (Contraindications to elective surgery):

1. Unstable coronary syndromes: Unstable angina, recent MI (within 30 days)
2. Decompensated heart failure (NYHA Class IV or new onset)
3. Significant arrhythmias: High-degree AV block, symptomatic ventricular arrhythmias, SVT with uncontrolled rate
4. Severe valvular disease: Severe AS, severe symptomatic MR

Functional Capacity (METs)

• Cannot assess = poor predictor of risk
• <4 METs (unable to climb stairs, walk on level ground) = poor functional capacity = higher risk
• >4 METs = acceptable functional capacity
• >10 METs = excellent functional capacity

10 MET: strenuous sports, swimming

Surgery Risk Stratification:

• Low risk (<1% MACE): endoscopy, cataract, breast
• Intermediate risk (1-5%): intraabdominal, intrathoracic, orthopaedic, head and neck, prostate
• High risk (>5%): aortic/major vascular, peripheral vascular

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3. PREOPERATIVE INVESTIGATIONS

ECG

• All patients with IHD
• Early ischemia: T-wave changes (inversion, peaking)
• More obvious ischemia: progressive ST-segment depression
  • Downsloping and horizontal ST depression > specificity than upsloping depression
• New ST elevation: STEMI - do NOT proceed with elective surgery

Stress Testing - Indications and Types

• Sensitivity 65%, Specificity 90%
• Most sensitive (85%) for 3-vessel or left main CAD
• Limitations: baseline ST changes, inability to reach 85% max HR
• Significant findings: ST depression at low workload, exercise-induced arrhythmias, BP drop with exercise

• For patients who cannot exercise (peripheral vascular disease, orthopaedic limitations) or have ECG abnormalities
• Pharmacological stress: dipyridamole or adenosine (coronary vasodilators)
• High sensitivity, fair specificity for CAD
• Perfusion defects filling in on redistribution = ischemia (not infarction)
• Fixed defect = scar
• Negative predictive value ~99%

• New/worsening wall motion abnormalities = significant ischemia
• EF <50%: more severe disease, higher perioperative morbidity
• Not reliable in LBBB (septal motion abnormal even without LAD disease)

• Gold standard
• Defines location and severity
• Stenosis >70% = significant; Left main >50% = critical

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4. PREOPERATIVE MANAGEMENT

Coronary Revascularization before Noncardiac Surgery

• NOT recommended purely to reduce perioperative cardiac events (Class III: No Benefit, Level B)
• Only indicated when revascularization is indicated on its own merits regardless of surgery

Key Drug Management:

Timing after Coronary Stenting - Critical Viva Point:

• Bare metal stent (BMS): wait at least 30 days before noncardiac surgery
• Drug-eluting stent (DES) - older generation: wait at least 12 months
• DES - newer generation: may proceed after 6 months (per updated ACC/AHA guidelines)
• Premature cessation of dual antiplatelet therapy → catastrophic stent thrombosis

Recent MI and Surgery Timing:

• Within 30 days: very high risk - delay elective surgery
• 31-60 days: still high risk

• 60 days: risk approaches baseline if revascularization complete and EF stable

• ACC/AHA: MI within 7 days = active cardiac condition (do not proceed electively)

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5. INTRAOPERATIVE MANAGEMENT

Monitoring

• Standard: ECG (V5 for ischemia detection - 75% sensitivity; V5+II = 90% sensitivity), SpO2, NIBP, EtCO2
• Invasive arterial line: severe CAD, major surgery, EF <40%, multiple risk factors
• CVP: large fluid shifts
• Pulmonary artery catheter: not routine; only if significant haemodynamic instability that cannot be corrected pre-op (Class IIb)
• TEE: emergency hemodynamic instability in noncardiac surgery (Class IIa); NOT routine (Class III)
• ST segment monitoring: continuous, 5-lead preferred

Anaesthetic Technique

• Volatile anaesthesia vs. TIVA: Either is acceptable - no proven superiority
• Volatile agents provide anaesthetic preconditioning (ischemic preconditioning-like protection) - this is a viva favourite
• Isoflurane, sevoflurane, and desflurane all provide this benefit

Key Intraoperative Goals:

1. HR control - target 50-70 bpm; avoid tachycardia
   • Use esmolol, metoprolol, or diltiazem
   • Beta-blockers are first line
2. Maintain coronary perfusion pressure = DBP - LVEDP
   • Avoid hypotension (especially diastolic)
   • Target DBP ≥60-65 mmHg
3. Preload: maintain adequate (not excessive)
4. Afterload: avoid extremes
5. Avoid ST-segment changes - monitor continuously
6. Normothermia (hypothermia → shivering → increased O2 demand; ACC/AHA Class IIb)
7. Adequate analgesia (reduce sympathetic activation)

Prophylactic Intraoperative Nitroglycerin:

• NOT recommended (Class III: No Benefit, Level B) - does not reduce myocardial ischemia in noncardiac surgery

Treatment of Intraoperative Ischemia:

1. Identify and treat the cause (tachycardia? hypotension? anemia? pain?)
2. Increase O2 delivery: FiO2 1.0, treat anaemia
3. Beta-blockers (esmolol) if tachycardic
4. IV nitroglycerin (reduces preload, dilates coronaries) - infusion 0.5-10 mcg/kg/min
5. Correct hypotension: phenylephrine (raises DBP without increasing HR)
6. Deepen anaesthesia if hypertension is the trigger

ECG Signs of Ischemia (in order of severity):

1. T-wave changes (earliest - inversion, hyperacute peaks)
2. ST depression (subendocardial ischemia) - most common intraoperatively
3. ST elevation (transmural/STEMI) - most severe
4. New Q waves (infarction - late)
5. LBBB (new onset = STEMI equivalent)

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6. SPECIFIC CLINICAL SCENARIOS

Patient on DAPT with Recent DES coming for Emergency Surgery

• Do NOT stop antiplatelet therapy (risk of acute stent thrombosis > surgical bleeding)
• Use platelet transfusion if significant bleeding occurs
• Regional anaesthesia: controversial if on DAPT - assess risk/benefit

Patient with Recent MI (within 60 days) Needing Emergency Surgery

• Proceed with maximal monitoring: art line, CVP, TEE if available
• Continue beta-blockers and statins
• Target HR <70, normotensive
• Have vasopressors and vasodilators ready
• Consider cardiology consultation

Patient with Low EF (<35%) for Noncardiac Surgery

• High-risk - discuss with cardiology/cardiac surgery pre-op
• Optimize heart failure treatment (diuretics, ACE inhibitors)
• Invasive monitoring
• Regional > general if feasible
• Avoid agents with negative inotropic effects
• Ketamine may be preferred for induction (maintains sympathetic tone)

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7. NEURAXIAL AND REGIONAL ANAESTHESIA IN IHD

Benefits:

• Reduces surgical stress response
• Neuraxial (epidural) analgesia reduces MI in patients undergoing abdominal aortic surgery (Class IIa, Level B)
• Preoperative epidural may decrease cardiac events in hip fracture patients (Class IIb, Level B)
• Reduced coagulability, reduced neurohumoral activation

Cautions:

• Sympathetic block → hypotension → reduced coronary perfusion pressure
• Bradycardia from high spinal → decreased HR may actually be beneficial in IHD (unless too slow)
• Must maintain DBP (phenylephrine preferred over ephedrine in IHD patients)

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8. POSTOPERATIVE MYOCARDIAL INFARCTION (POMI)

• Most common cause of perioperative mortality in noncardiac surgery
• Peak incidence: first 24-72 hours post-surgery
• Usually NSTEMI/demand ischemia type (not plaque rupture) in noncardiac surgery patients
• Often silent (masked by pain medications, sedation, residual anaesthesia)
• Troponin monitoring post-op in high-risk patients (ESC recommends routine troponin at 24 and 48 hours post-op in high-risk patients)
• Treatment: aspirin, anticoagulation, beta-blockers, urgent cardiology consultation
• Urgent PCI if STEMI or hemodynamically unstable

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QUICK-REFERENCE VIVA ANSWERS

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