Intraoperative handovers of anesthesia care are common.

Handovers might improve care by reducing physician fatigue, but there is also an inherent risk of losing critical information.

Large observational analyses report associations between handover of anesthesia care and adverse events, including higher mortality.

We determine the effect of handovers of anesthesia care on postoperative morbidity and mortality.

This was a parallel-group, randomized clinical trial conducted in 12 German centers with patients enrolled between June 2019 and June 2021 (final follow-up, July 31, 2021).

Eligible participants had an American Society of Anesthesiologists physical status 3 or 4 and were scheduled for major inpatient surgery expected to last at least 2 hours.

A total of 1817 participants were randomized to receive either a complete handover to receive anesthesia care by another clinician (n = 908) or no handover of anesthesia care (n = 909).

None of the participating institutions used a standardized handover protocol.nes