Anaesthetic Management of a Hypertensive Patient

(MD Anaesthesia PG Examination - 30 Marks)

OUTLINE

1. Definition and Classification
2. Pathophysiology Relevant to Anaesthesia
3. Preoperative Assessment
4. Preoperative Optimization - When to Postpone Surgery
5. Perioperative Drug Management
6. Intraoperative Monitoring
7. Induction of Anaesthesia
8. Maintenance of Anaesthesia
9. Intraoperative Hypertension - Management
10. Intraoperative Hypotension - Management
11. Postoperative Care and Complications

1. DEFINITION AND CLASSIFICATION

2. PATHOPHYSIOLOGY RELEVANT TO ANAESTHESIA

Cardiovascular Changes

• Early hypertension: elevated cardiac output with normal SVR
• Established hypertension: normal cardiac output but markedly elevated SVR (increased afterload)
• Chronic increased afterload causes concentric left ventricular hypertrophy (LVH)
• LVH leads to impaired diastolic function and diastolic dysfunction
• Increased oxygen demand with reduced coronary reserve
• LVH with strain pattern on ECG indicates chronic ischemic state

Cerebral Autoregulation

• Normal: autoregulation maintains CBF between MAP 60-160 mm Hg
• In chronic hypertension: autoregulatory curve is shifted to the right (MAP range ~110-180 mm Hg)
• Hypertensive patients require a higher MAP to maintain adequate CBF
• With antihypertensive treatment, the lower limit of autoregulation (LLA) can be partially restored toward normal, but restoration may be incomplete even after 12 months
• ACE inhibitors acutely decrease the LLA in both normotensive and hypertensive subjects
• Permissible acute reduction in MAP: not more than 30-35% from baseline; a 25% reduction may already bring patients to their LLA

Renal Changes

• Nephrosclerosis, microalbuminuria, reduced GFR
• Increased risk of perioperative acute kidney injury

Vascular Changes

• Endothelial dysfunction, arteriosclerosis, increased peripheral resistance
• Exaggerated pressor response to noxious stimuli
• Exaggerated hypotensive response to vasodilators and anaesthetic agents (depleted intravascular volume in some patients)

3. PREOPERATIVE ASSESSMENT

History

• Duration and severity of hypertension
• Antihypertensive medications (names, doses, compliance)
• Symptoms of end-organ damage: angina, dyspnea, PND, orthopnea, claudication, visual disturbances, TIA, headache
• Symptoms of secondary hypertension: paroxysmal hypertension + tachycardia/palpitations (pheochromocytoma), symptoms of hyperthyroidism, obstructive sleep apnea
• Comorbidities: diabetes, CKD, CAD, heart failure
• Illicit drug use (cocaine, anabolic steroids)

Physical Examination

• Blood pressure in both arms (coarctation of aorta suspected if discrepancy)
• Body weight and BMI
• Fundoscopy - hypertensive retinopathy (Keith-Wagener-Barker grading)
• Thyroid gland
• Cardiovascular system: S4 gallop (LVH), signs of heart failure, bruits (carotid, renal artery)
• Peripheral pulses
• Signs of coarctation (radio-femoral delay, lower BP in legs)

Investigations

4. PREOPERATIVE OPTIMIZATION - WHEN TO POSTPONE SURGERY

Decision Rule (widely accepted):

• BP <180/110 mm Hg: No strong evidence to delay elective surgery. Association between elevated BP and postoperative outcomes is not evident below these values. Proceed with surgery while continuing optimization.
• BP ≥180/110 mm Hg (severe hypertension): Weigh the benefit of delay to optimize BP control against the risk of delaying the procedure. The literature traditionally supports delaying elective surgery, but data do not clearly show that postponement reduces major morbidity when there are no end-organ changes. In the absence of end-organ changes (no renal insufficiency, no LVH with strain), the benefits of optimizing must be weighed against risks of delay.
• Emergency surgery: Proceed regardless of BP, with careful intraoperative hemodynamic management.
• End-organ damage present: Stronger indication to optimize BP before elective surgery.

Goals of Preoperative Optimization

• Achieve BP <160/100 mm Hg before elective surgery
• Correct hypokalemia from diuretics
• Identify and treat reversible secondary causes
• Optimize cardiac, renal function

5. PERIOPERATIVE DRUG MANAGEMENT

Drugs to CONTINUE on the Day of Surgery

Drugs to WITHHOLD on the Day of Surgery (or 24 h before)

6. INTRAOPERATIVE MONITORING

• Standard ASA monitoring in most hypertensive patients: NIBP, ECG (leads II + V5 for ischemia detection), SpO2, EtCO2, temperature
• Invasive arterial BP monitoring is reserved for:
  • Wide swings in blood pressure
  • Poorly controlled or severe hypertension
  • Major procedures with rapid preload/afterload changes (aortic surgery, major vascular procedures)
• Urinary catheter: for procedures >2 hours in patients with pre-existing renal impairment
• ECG focus: continuous monitoring for ischemic ST changes (hypertensive patients at higher risk for silent ischemia)
• Pulmonary artery catheter / TEE if severe LV dysfunction or diastolic dysfunction with expected large fluid shifts

7. INDUCTION OF ANAESTHESIA

Hemodynamic Challenges

1. Accentuated hypotensive response to induction agents - due to:
   • Vasodilatory effects of anaesthetic agents
   • Blunted baroreflexes from sympatholytic antihypertensives
   • Relative intravascular volume depletion (common in treated hypertensives)
2. Exaggerated hypertensive and tachycardic response to laryngoscopy and intubation - due to:
   • Heightened sympathoadrenal reactivity
   • Blunted baroreceptor buffering

Choice of Induction Agent

• No single agent has proven superiority in hypertensive patients
• Propofol, thiopentone, benzodiazepines, etomidate: all acceptable; choose based on patient's hemodynamic status
• Ketamine: can precipitate marked hypertension; avoid as sole agent. When combined with propofol or benzodiazepine, sympathomimetic effects are blunted
• Supplement all inductions with adequate opioid preloading

Techniques to Attenuate the Pressor Response to Intubation

1. Deepen anaesthesia with a potent volatile agent (increase concentration before laryngoscopy)
2. Opioid bolus before intubation:
   • Fentanyl 2.5-5 mcg/kg IV
   • Alfentanil 15-25 mcg/kg IV
   • Sufentanil 0.5-1.0 mcg/kg IV
   • Remifentanil 0.5-1 mcg/kg IV
3. Lidocaine 1.5 mg/kg IV (or intratracheal/topical) - attenuates airway reflexes
4. Beta-adrenergic blockade:
   • Esmolol 0.3-1.5 mg/kg IV
   • Metoprolol 1-5 mg IV
   • Labetalol 5-20 mg IV

8. MAINTENANCE OF ANAESTHESIA

Volatile Agents

• All modern volatile agents (sevoflurane, desflurane, isoflurane) are acceptable
• They cause dose-dependent vasodilation and blunt reflex sympathetic responses
• Sevoflurane and isoflurane preferred; desflurane can cause sympathetic activation at high concentrations or rapid increases
• Volatile agents help control intraoperative hypertension by increasing depth of anaesthesia

Neuraxial (Regional) Anaesthesia

• Both spinal and epidural anaesthesia are acceptable choices
• Epidural anaesthesia provides excellent hemodynamic control - gradual onset, titratable
• Advantages in hypertensive patients: reduces stress response, reduces postoperative pain-driven hypertension
• Risk of hypotension from sympathetic blockade - must have IV access and vasopressors ready
• Epidural opioids reduce the hemodynamic stress of surgery without hypotension

TIVA (Total Intravenous Anaesthesia)

• Propofol-remifentanil TIVA provides stable hemodynamics
• Remifentanil infusion excellent for attenuating pressor responses
• Useful where volatile agents are impractical

General Principles During Maintenance

• Maintain MAP within 20% of preoperative baseline
• Ensure adequate depth of anaesthesia before any noxious stimulus
• Muscle relaxants: avoid succinylcholine-induced fasciculations raising BP; vecuronium, rocuronium preferred (hemodynamically neutral)
• Avoid pancuronium (vagolytic tachycardia increases myocardial oxygen demand)
• Maintain normocarbia (hypercarbia causes sympathetic activation and hypertension)
• Adequate analgesia at all times

9. INTRAOPERATIVE HYPERTENSION

Definition

Causes (DAIT mnemonic)

• Depth of anaesthesia - inadequate
• Airway - hypoxia, hypercarbia
• Inadequate analgesia/pain
• Techincal - tourniquet inflation, bladder distension
• Drug/stimulant (cocaine, sympathomimetics)
• Clonidine/beta-blocker withdrawal
• Unrecognized pheochromocytoma
• Pre-existing poorly controlled hypertension

Management Stepwise

Parenteral Agents for Intraoperative Hypertension

• Good LV function + tachycardia: beta-blocker (esmolol, labetalol)
• Bronchospastic disease: CCB (nicardipine, clevidipine) - avoid beta-blockers
• Myocardial ischemia: nitroglycerin first choice
• Moderate to severe hypertension requiring rapid control: nitroprusside or clevidipine
• Renal impairment: fenoldopam
• Post-cardiac surgery: nitroglycerin (for revascularized patients) or nitroprusside (if arterial vasoconstriction predominates)

10. INTRAOPERATIVE HYPOTENSION

Definition

Causes in Hypertensive Patients (specific vulnerabilities)

• Sympatholytic antihypertensives + vasodilatory anaesthetic agents
• Volume depletion (diuretics, poor oral intake)
• ACEI/ARB taken preoperatively - blocks angiotensin II-mediated vasoconstrictive response; refractory to indirect-acting vasopressors

Management

1. Reduce anaesthetic depth
2. IV fluid bolus (assess volume status first)
3. Vasopressors:
   • Phenylephrine 25-50 mcg IV bolus (direct alpha agonist - preferred when tachycardia present)
   • Ephedrine 5-10 mg IV (indirect-acting; note: patients on sympatholytics may show decreased response to ephedrine)
   • Vasopressin bolus or infusion - useful in refractory hypotension due to ACEI/ARB
   • Norepinephrine infusion - restores vascular tone in vasodilatory hypotension

11. POSTOPERATIVE CARE

Postoperative Hypertension

• Pain - most common cause
• Anxiety
• Emergence agitation
• Hypoxia, hypercarbia
• Bladder distension
• Hypothermia and shivering (increased SVR)
• Withdrawal from preoperative antihypertensives (especially beta-blockers, clonidine)
• Fluid overload

• Increased myocardial oxygen demand and risk of MI
• Rhythm disturbances
• Cerebrovascular accident
• Increased surgical site bleeding
• Anastomotic/suture line disruption (especially in vascular surgery)

• Treat underlying cause first (analgesia, re-warming, O2)
• Resume preoperative antihypertensives as soon as oral intake is possible
• IV antihypertensives as above if required
• Ensure ACEI/ARB are restarted once hemodynamically stable - failure to restart is associated with adverse outcomes

Monitoring

• Continue BP monitoring with frequency based on degree of preoperative hypertension and intraoperative course
• Monitor for ischemic ECG changes, urine output (renal function), neurological status

Analgesia

• Effective multimodal analgesia is essential to prevent pain-driven postoperative hypertension
• Regional analgesia, NSAIDs (with caution in renal impairment), paracetamol, opioids as needed

KEY POINTS TO REMEMBER (Exam Summary)

1. Hypertension = BP >140/90 (ISH) or >130/80 (ACC/AHA 2017); affects ~45% of adults
2. Essential hypertension 80-95%; always screen for secondary causes
3. Postpone elective surgery if BP ≥180/110 mm Hg (especially with end-organ damage)
4. Below 180/110 mm Hg - no strong evidence that postponement improves outcomes
5. Continue beta-blockers, CCBs, alpha-2 agonists perioperatively; withhold ACEI/ARB 24 h before surgery
6. Restart ACEI/ARB postoperatively - failure to restart is associated with adverse outcomes
7. Autoregulation curve shifted right - keep MAP within 20% of baseline; do not reduce MAP >30-35% from baseline
8. Induction: exaggerated hypotension followed by exaggerated hypertensive response to intubation - attenuate with opioids, lidocaine, beta-blockers
9. Ketamine alone is relatively contraindicated; can use with benzodiazepine/propofol
10. Avoid pancuronium; prefer vecuronium/rocuronium
11. Treat intraoperative hypertension: exclude hypoxia/hypercarbia first, then deepen anaesthesia, then parenteral agents
12. Labetalol (alpha+beta): no reflex tachycardia; excellent for most situations
13. Beta-blockers contraindicated in bronchospasm - use nicardipine/clevidipine instead
14. Fenoldopam increases renal blood flow - preferred in renal impairment
15. Postoperative: aggressive multimodal analgesia, monitor for ischemia, resume antihypertensives

• Morgan and Mikhail's Clinical Anesthesiology, 7th Edition (pp. 714-723)
• Miller's Anesthesia, 10th Edition (pp. 1077-1078, 3867-3869, 7499-7500)
• Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition (pp. 1761-1762)