Impact of BMI ≥40 kg/m2 on ASA-PS Classification in Metabolic Surgery
Overview
This study evaluates whether assigning ASA-PS III classification solely based on a BMI ≥ 40 kg/m2 accurately reflects peri-operative risk in metabolic surgery patients. Using data from the Dutch Audit for Treatment of Obesity, it compares complication rates between patients classified by BMI alone and those with severe systemic diseases.
Background
The ASA-PS classification system has been used since 1941 to assess peri-operative risk, with BMI ≥ 40 kg/m2 added as a criterion in 2014. Obesity is linked to metabolic abnormalities increasing risks for diabetes, cardiovascular disease, and mortality. However, not all patients with high BMI exhibit metabolic complications, as metabolically healthy obesity exists. The impact of BMI alone on peri-operative risk and ASA-PS classification accuracy remains unclear, especially in metabolic surgery.
Data Highlights
The study analyzed data from the Dutch Audit for Treatment of Obesity (DATO) registry, including patients aged under 75 years undergoing primary metabolic surgery between 2015 and 2023. Patients were grouped by BMI and comorbidity status: (1) BMI 30–40 kg/m2 without/mild systemic disease, (2) BMI ≥ 40 kg/m2 without/mild systemic disease, and (3) BMI < 40 kg/m2 with severe systemic disease. The Charlson Comorbidity Index was used to define severity of systemic disease. Cases with missing key data were excluded.
Key Findings
ASA-PS III classification is often assigned solely based on BMI ≥ 40 kg/m2 despite absence of severe systemic disease.
Patients with ASA-PS III classification based only on BMI ≥ 40 kg/m2 exhibit lower rates of peri-operative complications compared to those with ASA-PS III due to severe systemic diseases.
Increased BMI alone does not reliably predict higher peri-operative morbidity or mortality in metabolic surgery.
Metabolically healthy obesity phenotype may explain lower complication rates despite high BMI.
Current ASA-PS classification may overestimate peri-operative risk in patients classified solely by BMI ≥ 40 kg/m2.
Clinical Implications
Clinicians should consider that a BMI ≥ 40 kg/m2 alone may not justify a higher ASA-PS classification without evidence of severe systemic disease. Risk stratification for metabolic surgery patients should incorporate metabolic health and comorbidity profiles rather than relying solely on BMI. This approach may improve peri-operative risk assessment and optimize patient management.
Conclusion
Assigning ASA-PS III classification solely based on BMI ≥ 40 kg/m2 does not accurately reflect peri-operative risk in metabolic surgery patients. Incorporating comorbidity status alongside BMI provides a more precise risk stratification.
References
DATO Registry 2022 -- Dutch Audit for Treatment of Obesity
