PAAB: withholding angiotensin blockers before surgery did not reduce harm

Design

Single-centre, single-blind randomised trial (PAAB)

Population

638 adults on ACE inhibitors or ARBs having elective non-cardiac surgery

Primary outcome

Major adverse cardiovascular events at five days

Effect

2.8% v 2.9%, difference 0.1% (−2.5 to 2.8); AKI 7.4% v 4.8%, NS

Many perioperative protocols ask patients without hypertension or systolic heart failure to omit ACE inhibitors and ARBs for 24 hours before surgery, on the theory that it reduces intraoperative hypotension and kidney injury. PAAB, a single-centre, single-blind trial in the Journal of Hospital Medicine (19 September), tested that in 638 patients (mean age 66) on a stable dose, randomised at a preoperative clinic before elective non-cardiac surgery.

Major cardiac events within five days occurred in 2.8% who continued and 2.9% who withheld (difference 0.1%, 95% CI −2.5 to 2.8). Intraoperative hypotension was common in both groups (63.5% v 60.7%) and acute kidney injury was, if anything, numerically lower with withholding (7.4% v 4.8%) without reaching significance. No subgroup differed.

For physicians doing preoperative assessment, this adds randomised evidence that the 24-hour hold does not deliver its intended benefit in low-risk patients — and every omitted dose is a dose that may not be restarted after surgery. The trial was small, single-centre and not powered for rare events, so local protocols and guidelines have not changed on its strength. Where the decision is yours, either approach looks reasonable; what matters most is a documented plan to restart.

• Continuing or withholding ACE inhibitors or ARBs for 24 hours led to similar outcomes in low-risk surgery.
• Follow your local perioperative protocol, but do not expect withholding to prevent hypotension.
• Write an explicit restart plan for any angiotensin blocker held around surgery.
• Check creatinine and potassium after surgery whichever approach you take.

Why it matters

It challenges a widespread preoperative instruction that has rested on little evidence.

Don't overread it

One centre, low-risk patients and only 18 primary events; this does not cover heart failure or high-risk surgery.

The statistics, in plain English

The difference in cardiac events was 0.1 percentage point, with a confidence interval from −2.5 to 2.8 — so the trial rules out large effects either way, but with only 18 events it cannot exclude small ones. The kidney injury difference (7.4% v 4.8%) looks meaningful but its interval crosses zero, so it may be chance.

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