ACE Inhibitors Should Be Stopped 24 Hours Before Surgery
In patients taking ACE inhibitors for hypertension who are undergoing elevated-risk noncardiac surgery, stop the medication 24 hours before the procedure to reduce intraoperative hypotension and vasopressor requirements. 1, 2, 3
Rationale for Withholding
The physiological basis for stopping ACE inhibitors preoperatively is well-established:
During anesthesia and surgery, the body experiences inhibition of the sympathetic nervous system by anesthetics, loss of baroreceptor control, and relative hypovolemia from preoperative fasting. 2
ACE inhibitors block the compensatory renin-angiotensin-aldosterone system, which is critical for maintaining vascular tone and blood pressure during surgical stress. 2
Without angiotensin II's compensatory vasoconstriction, patients experience more significant blood pressure drops after anesthesia induction and require increased vasopressor support. 2
Evidence Supporting 24-Hour Discontinuation
Recent high-quality evidence demonstrates clear benefits:
Patients who discontinued ACE inhibitors 24 hours before surgery had lower rates of death, stroke, myocardial injury, and intraoperative hypotension compared to those continuing therapy. 2, 4
A 2024 retrospective cohort study of 42,432 patients showed that withholding ACE inhibitors reduced myocardial injury after noncardiac surgery (6.4% vs 7.4%) and decreased intraoperative hypotension. 5
Early studies from 1994 demonstrated that 100% of patients continuing enalapril until surgery required ephedrine after induction, compared to significantly fewer when therapy was stopped. 6
Critical Exception: Heart Failure with Reduced Ejection Fraction
In patients taking ACE inhibitors for heart failure with reduced ejection fraction (HFrEF), continue the medication perioperatively with close hemodynamic monitoring. 1, 2, 3
The cardioprotective benefits in systolic left ventricular dysfunction (EF ≤40%) outweigh the hypotension risks. 2, 3
This represents a Class IIa recommendation from the American College of Cardiology guidelines. 3
Postoperative Resumption Protocol
Restart ACE inhibitors when the patient is hemodynamically stable with systolic blood pressure >100 mmHg and adequate volume status. 2, 3, 4
Resume as soon as clinically feasible postoperatively, typically within 24 hours after surgery when volume status is stable. 3, 4
Restarting too early can precipitate hypotension; ensure adequate intravascular volume before resumption. 2
Management of Intraoperative Hypotension
If refractory hypotension occurs despite withholding ACE inhibitors:
Low-dose vasopressin (0.5-2 units bolus) or vasopressin analogues effectively treat ACE inhibitor-associated refractory hypotension that doesn't respond to catecholamines. 7
All patients receiving vasopressin demonstrated improved hemodynamic stability without profound ischemic changes. 7
Common Pitfalls to Avoid
Do not confuse the 24-hour discontinuation window for ACE inhibitors with the 5-day window for vitamin K antagonists or 7-10 day window for antiplatelet agents. 1
Do not withhold ACE inhibitors in patients with HFrEF; the indication matters more than the drug class. 1, 2
Do not restart ACE inhibitors in the immediate postoperative period if the patient remains hypovolemic or hypotensive. 2, 4
The morning dose should be held even if the patient takes the medication twice daily; this means the last dose should be at least 24 hours before surgery. 7, 6