Should there be a body mass index eligibility cutoff for elective airway cases in an ambulatory surgery center? A retrospective analysis of adult patients undergoing outpatient tonsillectomy.

Study Objective: It is unclear what the body mass index (BMI) should be when performing surgery involving the airway at an outpatient surgery facility. The objective of this study was to evaluate the association of Class 3 obesity versus a composite cohort of Class 1 and 2 obesity with same-day hospital admission following outpatient tonsillectomy in adults.

Design: Retrospective cohort study.

Setting: Multi-institutional.

Patients: Patients undergoing outpatient tonsillectomy.

Intervention: None.

Measurements: We used the National Surgical Quality Improvement Program (NSQIP) to analyze association of BMI to same-day admission and 30-day readmission following outpatient tonsillectomy from 2017 to 2019. We looked at six BMI cohorts: 1) ≥30 and < 40 kg/m (reference cohort), 2) ≥20 and < 30 kg/m, 3) <20 kg/m, 4) ≥40 and < 50 kg/m, 5) ≥50 and < 60 kg/m, and 6) ≥60 kg/m. We used multivariable Poisson regression with robust standard errors and controlled for various confounders to calculate risk ratios (RR) and 99% confidence intervals (CI).

Main Results: There were 12,287 patients included in the final analysis, at which 697 (5.7%) and 283 (2.3%) had a same-day admission or 30-day readmission, respectively. On Poisson regression with robust standard errors, the relative risks for BMI ≥40 kg/m and < 50 kg/m, ≥50 kg/m and < 60 kg/m, and ≥ 60 kg/m (BMI ≥30 kg/m and < 40 kg/m was the reference group) were 1.31 (99% CI 1.03-1.65, p = 0.03), 1.99 (99% CI 1.43-2.78, p = 0.002), and 1.80 (99% CI 1.00-3.25, p = 0.07), respectively. Furthermore, Class 3 obesity was not associated with 30-day readmission.

Conclusion: These results contribute data that may help practices - especially freestanding ambulatory surgery centers - decide appropriate BMI cutoffs for surgery involving the airway. Whether this is considered clinically significant enough to rule out eligibility will differ from practice-to-practice and will depend on surgical volume, resources available and financial interests.