Impact of body mass index on surgical case durations in an academic medical center

Study objective: To investigate the association between patient body mass index (BMI) and operating room duration. Design: Retrospective cohort analysis.Setting: Demographic data and anesthesia/surgical times for adult surgical patients at University of Virginia Health between August 2017 and February 2019 were collected and analyzed.Patients: A total of 31,548 cases were included in the final analysis. 55% of patients were female, and 51% were classified as ASA Physical Status 2. The mean operating room (OR) duration was 144.2 min & PLUSMN; 112.7 (median = 118, IQR = 121). Orthopedic surgery (32%) was the most common surgery.Measurements: Linear mixed effects models were used to examine whether procedure intervals differed across three BMI categories (BMI < 30, 30 < BMI < 40, BMI > 40), considering within-surgeon correlations. Surgical times were log-transformed to correct for positive skewness.Main results: The average time in the operating room was longer for patients with higher BMI (mean & PLUSMN; SD [median, IQR] = 139.5 & PLUSMN; 111.2 [113.0, IQR = 114], 150.2 & PLUSMN; 115.4 [125, IQR = 127], and 153.1 & PLUSMN; 111.1 [130, IQR = 134] for BMI < 30, 30 < BMI < 40, and BMI > 40), respectively. We found a 2% [95% CI = 1-3%] and 3% [95% CI = 1-5%] increase in OR time for 30 < BMI < 40 and BMI > 40, respectively, compared to BMI < 30, after controlling for within-surgeon correlations and covariates. The excess time was primarily determined by anesthesia times.Conclusion: In an academic hospital, patients with BMI > 30 required more time in the operating room than patients with BMI < 30, when controlling for confounders. This information can be incorporated into modernday OR scheduling software, potentially resulting in more accurate case duration estimates that reduce waiting and improve OR efficiency.