What is the best approach to manage a patient's hypertension before a scheduled surgery?

Management of Hypertension Before Scheduled Surgery

Elective surgery should proceed if blood pressure is below 180/110 mmHg, and patients with blood pressure between 140/90 and 180/110 mmHg should have their primary care physician notified but surgery should not be delayed. 1

Blood Pressure Thresholds for Proceeding with Surgery

The critical threshold is 180/110 mmHg - this is the blood pressure level that determines whether elective surgery can proceed without delay 1, 2:

• BP < 180/110 mmHg: Proceed with elective surgery 1
• BP ≥ 180/110 mmHg: Refer back to primary care for blood pressure optimization before non-urgent surgery 1
• BP 140/90 to 179/109 mmHg: Inform the GP for concurrent hypertension management, but do not postpone elective surgery 1

Pre-Operative Blood Pressure Assessment Algorithm

Primary Care Responsibilities

• Blood pressure should be measured in primary care before non-urgent surgical referral 1
• If BP is ≥160/100 mmHg, reduction to <160/100 mmHg should precede non-urgent surgical referral 1
• Document blood pressure measurements from the past 12 months in the referral letter 1

Pre-Operative Assessment Clinic Protocol

When patients arrive without documented BP readings 1:

1. Measure BP up to three times, at least one minute apart, with the patient seated and arm supported 1
2. Record the lower of the last two readings 1
3. If BP < 180/110 mmHg: Proceed with surgery but inform GP if BP >140/90 mmHg 1
4. If BP ≥ 180/110 mmHg: Return patient to primary care for management 1

Perioperative Medication Management

Continue Most Antihypertensive Medications

Most antihypertensive medications should be continued perioperatively 2, 3:

• Continue beta-blockers, calcium channel blockers, and thiazide diuretics through the day of surgery 1
• Abrupt withdrawal of beta-blockers can precipitate rebound hypertension and silent myocardial ischemia 1, 2
• Sudden withdrawal of clonidine or alpha-methyldopa is also associated with adverse events 1

Consider Withholding ACE Inhibitors and ARBs

Omitting ACE inhibitors and ARBs on the day of surgery may reduce intraoperative hemodynamic fluctuations 1, 2, 3:

• This practice is associated with less intraoperative hypotension 3
• These medications can be carefully reintroduced after surgery 1, 2
• Discontinuing these agents appears to reduce perioperative morbidity and mortality 3

Initiating or Optimizing Antihypertensive Therapy

If hypertension is newly diagnosed or poorly controlled before surgery, treatment should follow a stepwise approach 1:

Step 1: Initial Monotherapy

Age < 55 years 1:

• Offer ACE inhibitor or low-cost ARB 1
• If ACE inhibitor causes cough, switch to ARB 1
• Avoid ACE inhibitors/ARBs in women of childbearing potential 1

Age ≥ 55 years or Black patients of any age 1:

• Offer calcium channel blocker (CCB) 1
• If CCB not suitable (edema, intolerance) or heart failure present, offer thiazide-like diuretic 1
• Prefer chlorthalidone (12.5-25 mg daily) or indapamide (1.5 mg modified-release or 2.5 mg daily) over conventional thiazides 1

Step 2: Dual Therapy

• Combine CCB with either ACE inhibitor or ARB 1
• For Black patients, prefer ARB over ACE inhibitor when combining with CCB 1
• If CCB unsuitable, use thiazide-like diuretic instead 1

Step 3: Triple Therapy

• Ensure Step 2 drugs are at optimal or maximum tolerated doses before adding third agent 1
• Use combination of ACE inhibitor or ARB + CCB + thiazide-like diuretic 1

Step 4: Resistant Hypertension

If BP remains ≥140/90 mmHg on triple therapy 1:

• Add low-dose spironolactone (25 mg daily) if serum potassium <4.6 mmol/L 1, 4, 5
• Monitor serum sodium, potassium, and renal function within 1 month 1
• If spironolactone contraindicated or ineffective, consider alpha-blocker or beta-blocker 1
• Seek expert advice if BP uncontrolled on four drugs 1

Anesthetic Considerations for Hypertensive Patients

Hypertensive patients demonstrate more labile hemodynamics during anesthesia 1, 2:

• Induction and airway instrumentation trigger pronounced sympathetic activation with significant BP and heart rate increases 2
• Implement techniques for hemodynamic stability: co-induction, invasive arterial monitoring with titrated vasopressor therapy, depth-of-anesthesia monitoring, and stroke volume optimization 1, 2

Critical Pitfalls to Avoid

• Never abruptly discontinue beta-blockers - this can cause rebound hypertension and silent myocardial ischemia that may be missed without continuous ECG monitoring and serial troponin measurements 1, 2
• Do not combine ACE inhibitors with ARBs - this increases adverse effects without additional benefit 1, 4
• Do not initiate beta-blockers perioperatively in high-risk patients - this increases postoperative mortality from hypotension and stroke 1
• Monitor electrolytes carefully with aldosterone antagonists - particularly in patients with reduced renal function 1, 4
• Emergency surgery must proceed regardless of BP control - all parties should be aware of associated increased risk 2

Special Populations

Patients ≥80 years 1:

• Offer treatment only if Stage 2 hypertension (BP ≥160/100 mmHg) 1
• Treatment has demonstrated clinical benefits and cost-effectiveness in this age group 1

Patients with well-controlled hypertension on existing therapy 1:

• Continue bendroflumethiazide or hydrochlorothiazide if BP is stable and well controlled 1
• Do not change effective regimens unnecessarily 1