Why is telmisartan (an angiotensin‑II receptor blocker) withheld on the day of surgery?

Why Telmisartan is Withheld on the Day of Surgery

Telmisartan should be withheld on the morning of surgery because continuing angiotensin-II receptor blockers (ARBs) significantly increases the risk of intraoperative hypotension, which can be severe, prolonged, and require vasopressor treatment. 1

The Core Problem: Intraoperative Hypotension

When telmisartan and other ARBs are continued on the day of surgery, they block the renin-angiotensin system's ability to maintain blood pressure during anesthesia. This creates a perfect storm:

• Anesthesia itself causes vasodilation through multiple mechanisms: loss of baroreceptor reflex control, direct effects of anesthetic agents on vascular tone, and potential neuraxial blockade 1
• ARBs prevent the compensatory response by blocking angiotensin II's vasoconstrictor effects at the AT₁ receptor 2
• The result is more frequent, more severe, and longer-lasting hypotensive episodes that require aggressive vasopressor intervention

The Evidence Base

The most recent 2024 AHA/ACC guidelines explicitly state that angiotensin-receptor blockers have been associated with increased risk of intraoperative hypotension when continued 3. This is not theoretical—the clinical impact is substantial:

Quantified Risk from Research Studies

A 2025 meta-analysis of randomized controlled trials demonstrated that withholding ACEIs/ARBs before surgery resulted in 4:

• Reduced intraoperative hypotension: 36.4% vs 48.4% (a 25% relative risk reduction)
• Shorter duration of hypotension: 5.4 minutes less on average
• Less vasopressor use: 37.5% vs 51.2%

An earlier 2001 randomized study showed even more dramatic differences when ARBs were continued 5:

• More hypotensive episodes per patient: 2±1 vs 1±1 episodes
• More patients experiencing hypotension: 100% vs 67%
• Longer hypotensive episodes: 8±7 minutes vs 3±4 minutes
• Increased vasopressor requirements

The Hemodynamic Mechanism

Telmisartan has a peak effect 0.5-1 hour after oral administration and inhibits approximately 90% of the pressor response to angiotensin II at peak concentrations, with 40% inhibition persisting for 24 hours 2. When you induce anesthesia in a patient who took telmisartan that morning:

1. The drug is at or near peak concentration
2. Anesthesia causes vasodilation and sympathetic blockade
3. The body attempts to compensate via the renin-angiotensin system
4. This compensatory mechanism is blocked by telmisartan
5. Blood pressure drops precipitously and cannot self-correct

Clinical Practice Recommendation

The omission of angiotensin-receptor blockers on the day of surgery, combined with careful reintroduction after surgery, is commonplace and appears to be associated with fewer significant perioperative hemodynamic fluctuations 1.

Practical Implementation:

• Hold telmisartan on the morning of surgery (ideally 24 hours before, but at minimum the morning dose)
• Resume postoperatively once the patient is hemodynamically stable and taking oral medications
• Use IV antihypertensives intraoperatively if needed to control blood pressure 3
• Monitor for rebound hypertension postoperatively, which occurs more frequently when ARBs are withheld (27.8% vs 20.2%) but is generally manageable 4

Important Caveats

What About Mortality and Major Complications?

Multiple meta-analyses have not demonstrated that continuing ARBs increases mortality or major adverse cardiac events 4, 6. The 2018 meta-analysis found no association with mortality (OR 0.97) or MACE (OR 1.12) 6. However, intraoperative hypotension itself is associated with postoperative myocardial injury, acute kidney injury, and mortality when MAP <65 mmHg or SBP <90 mmHg is maintained for approximately 15 minutes 3.

The lack of demonstrated mortality difference likely reflects:

• Anesthesiologists aggressively treating hypotension with vasopressors
• The relatively short duration of most surgeries
• The fact that most studies were underpowered for rare outcomes

The SPACE Trial Nuance

Recent 2024 data from the SPACE trial showed no significant difference in myocardial injury between stopping and continuing ACEIs/ARBs 7. However, this trial had important limitations and patients randomized to continue experienced more intraoperative hypotension requiring intervention—the trial simply didn't show this translated to worse outcomes, possibly because hypotension was aggressively managed.

Bottom Line Algorithm

For patients on chronic telmisartan presenting for surgery:

1. Hold the morning dose on the day of surgery (or ideally 24 hours prior)
2. Maintain other antihypertensives (beta-blockers, calcium channel blockers) to avoid rebound hypertension
3. Prepare for potential postoperative hypertension with IV agents if needed
4. Resume telmisartan postoperatively once hemodynamically stable and tolerating oral intake
5. Never abruptly discontinue beta-blockers or clonidine, as these cause dangerous rebound hypertension 3, 1

The practice of withholding ARBs like telmisartan on the day of surgery is supported by both guideline recommendations and consistent evidence showing reduced intraoperative hypotension, even though hard outcome data remain somewhat equivocal 3, 1, 4.