For an adult patient scheduled for elective surgery tomorrow under spinal anaesthesia, should ACE inhibitor/ARB and diuretic be held on the day of surgery to avoid peri‑operative hypotension?

Perioperative Management of ACE Inhibitors/ARBs and Diuretics Before Spinal Anesthesia

Yes, you should hold ACE inhibitors/ARBs on the day of surgery to prevent severe intraoperative hypotension, particularly under spinal anesthesia where RAAS blockade combined with sympathetic blockade creates compounded hypotensive risk. 1, 2

Evidence-Based Rationale for Holding RAAS Blockers

The ACC/AHA guidelines provide a Class IIb recommendation (may be considered) to discontinue ACE inhibitors or ARBs perioperatively, based on cohort evidence showing that patients who stopped these medications 24 hours before surgery had lower rates of death, stroke, myocardial injury, and intraoperative hypotension compared to those continuing them. 1, 2

The mechanism is clear: ACE inhibitors and ARBs block compensatory vasoconstriction during anesthesia-induced hypotension. When combined with spinal anesthesia's sympathetic blockade, this creates a "double hit" that can result in severe, refractory hypotension requiring significantly higher vasopressor doses. 3, 4

• A controlled case report demonstrated that continuing enalapril before spinal anesthesia required more than 5 times the vasopressor dose compared to when it was stopped 48 hours earlier. 3
• Meta-analysis of 6,022 patients confirmed that withholding ACE-I/ARB therapy significantly reduced intraoperative hypotension (OR 0.63,95% CI 0.47-0.85) without increasing mortality or major cardiac events. 4

Specific Management Algorithm

ACE Inhibitors/ARBs

• Hold the morning dose on the day of surgery (ideally discontinue 24 hours before). 1, 2
• Restart as soon as the patient is hemodynamically stable, volume-replete, and tolerating oral intake postoperatively. 2, 5
• The short-term discontinuation (24 hours) does not increase cardiovascular risk. 4

Diuretics

• Consider holding diuretics on the morning of surgery, particularly for spinal anesthesia where fluid restriction is recommended. 1
• The British guidelines specifically recommend restricting IV fluids to no more than 500 mL for spinal anesthesia to reduce urinary retention risk, making preoperative diuretic use counterproductive. 1
• Restart when oral intake resumes and volume status is adequate. 1

Critical Medications to CONTINUE

Beta-blockers must be continued (Class I recommendation) to avoid rebound hypertension and increased cardiac risk—abrupt discontinuation is potentially harmful. 1, 5

Calcium channel blockers should be continued through the day of surgery as they do not cause significant intraoperative hypotension and may reduce perioperative ischemia. 2, 5

Clonidine must be continued to avoid dangerous rebound hypertension. 1, 2

Intraoperative Hypotension Management

If hypotension develops after holding ACE-I/ARBs, use IV vasopressors rather than regretting the decision to hold them:

• First-line agents: Clevidipine, esmolol, nicardipine, or nitroglycerin for perioperative hypertension. 1, 2
• For hypotension: Standard vasopressors (phenylephrine, ephedrine) will be more effective when RAAS is not blocked. 3
• The hypotension from holding these medications is far easier to manage than the refractory hypotension that occurs when they're continued. 3, 4

Common Pitfalls to Avoid

Do not continue ACE-I/ARBs thinking you're preventing hypertensive peaks—the risk of severe intraoperative hypotension outweighs any benefit, and blood pressure can be managed with IV agents if needed. 2, 3, 6

Do not hold beta-blockers or clonidine even if you're holding ACE-I/ARBs—these create dangerous rebound phenomena that are more harmful than controlled RAAS blocker discontinuation. 1, 2

Do not defer surgery solely because ACE-I/ARBs are held—surgery can proceed safely at blood pressures <180/110 mmHg even without these medications for 24 hours. 1, 7

Blood Pressure Thresholds for Proceeding

• Proceed with surgery if BP <180/110 mmHg after holding ACE-I/ARBs. 1, 7
• Consider deferring elective surgery if BP ≥180/110 mmHg despite holding these medications. 1
• Target BP <130/80 mmHg is reasonable before major elective procedures, but achieve this with medications other than ACE-I/ARBs in the immediate preoperative period. 2, 5

Special Considerations for Spinal Anesthesia

The combination of spinal anesthesia and ACE-I/ARB therapy is particularly problematic:

• Spinal anesthesia causes sympathetic blockade with vasodilation and reduced venous return. 1, 3
• ACE-I/ARBs prevent compensatory RAAS activation. 3, 4
• This "double blockade" creates profound, difficult-to-treat hypotension. 3, 6
• Low-dose spinal techniques and fluid restriction (≤500 mL) further limit hemodynamic reserve. 1

The evidence strongly supports holding ACE-I/ARBs before spinal anesthesia specifically, with some authors recommending discontinuation 48 hours in advance for this indication. 3, 6