The role of the BMI ≥40 kg/m² criterium in ASA-PS classification for metabolic surgery

Purpose This study explores historical trends in ASA-PS scoring and evaluates whether the ASA-PS III classification based solely on a BMI ≥ 40 kg/m² effectively contributes to peri-operative risk stratification for patients undergoing metabolic surgery. Methods Adult patients (January 2015-January 2023) were included from the Dutch Audit for the Treatment of Obesity registry. Logistic regression adjusted for confounders compared groups stratified by BMI and presence of systemic disease. Outcome measures: complication prevalence (peri-operative, ≤30days and >30days), Clavien-Dindo score, hospital stay (>2 days), ICU admission, readmission, and mortality rates. Results A total of 75,871 patients (78.8% women, age 43.5 (SD 11.8) yrs, BMI 42.9 (SD 5.3) kg/m ² ) were included. The number of patients receiving ASA-PS III increased from 26% to 92% (BMI≥40 kg/m ² ), and from 20% to 64% (BMI<40 kg/m ² ), despite generally stable mean age, BMI, and concurrent diseases. From 2018, ASA-PS II was inaccurately assigned in 64%. Patients without severe systemic disease (BMI ≥ 40 kg/m ² ) were significantly less likely to experience complications, ICU admission, prolonged hospital stay, or readmission compared to patients with severe systemic disease (BMI < 40 kg/m²) (OR: 1.72, 95% CI: 1.43 – 2.08, p < 0.001). Conclusion A large Dutch national registry on metabolic surgery showed that ASA-PS III patients with BMI ≥ 40 kg/m² only were less likely to experience complications after surgery compared to those with BMI < 40 kg/m² and severe systemic disease. This suggests that adhering to the BMI criterion may undermine the ASA-PS classification's effectiveness in risk stratifying these patients.