Extended Work Periods Among Anesthesiologists and Postoperative Patient Outcomes.

Importance: Attending anesthesiologists are not subject to work hour restrictions. Fatigue from long shifts may plausibly contribute to patient harm. Objective: To examine the association between anesthesiologist extended work periods and patient outcomes. Design, Setting, and Participants: This cross-sectional study used data from the Multicenter Perioperative Outcomes Group registry from January 1, 2010, to August 30, 2020, representing all surgical procedures in patients 18 years or older from more than 50 hospitals across 18 US states. Data analyses were conducted from July 1 through November 30, 2025. Exposure: Anesthesiologist extended work periods, defined as 16 hours or more of continuous intraoperative work. Main Outcomes and Measures: The primary outcome was a composite of in-hospital mortality or major complication. Secondary outcomes were individual components of the composite. A within-anesthesiologist approach was used to compare outcomes for patients treated by each anesthesiologist when in an extended work period vs not, adjusting for patient demographics, comorbidities, American Society of Anesthesiologists classification, emergency status, hour of surgery start, and surgery type. Results: The study cohort comprised 1 648 720 surgical procedures involving 1711 unique anesthesiologists across 36 institutions (patient mean [SD] age, 51.7 [17.8] years; 982 020 [59.6%] female). A total of 11 556 procedures (0.7%) involved anesthesiologists in an extended work period. Unadjusted incidence of the composite outcome was 12.3% (95% CI, 11.7%-12.9%) for extended work periods vs 12.0% (95% CI, 12.0%-12.1%) for standard work periods. Adjusted absolute risk difference in the composite outcome was 0.1% (95% CI, -0.4% to 0.5%; P = .82). Multiple sensitivity analyses resulted in statistical significance with point estimates of similar direction and magnitude. In-hospital mortality was higher for extended (1.3%; 95% CI, 1.1%-1.6%) vs standard (1.0%; 95% CI, 1.0%-1.0%) work periods, with a risk difference of 0.3 (95% CI, 0.1%-0.5%; P = .009). Other secondary outcomes had risk increases of similar magnitude. Conclusions and Relevance: In this cross-sectional study, the primary analysis did not identify a statistically significant difference in composite outcome, although the magnitude and precision of risk estimates across multiple sensitivity analyses suggested a small (<1.0%) increase in risk. Secondary analyses also suggested small absolute increases in outcomes, including in-hospital mortality. These findings raise the possibility that fatigue related to prolonged anesthesiologist work periods may have implications for patient safety.