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 ± 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 ± SD [median, IQR] = 139.5 ± 111.2 [113.0, IQR = 114], 150.2 ± 115.4 [125, IQR = 127], and 153.1 ± 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 modern-day OR scheduling software, potentially resulting in more accurate case duration estimates that reduce waiting and improve OR efficiency.