Does ASA classification effectively risk stratify patients undergoing bariatric surgery: a MBSAQIP retrospective cohort of 138,612 of patients

It is important to appropriately risk stratify bariatric surgery patients, as these patients often have obesity-related comorbidities which can increase postoperative complication risk but also benefit the most from bariatric surgery. We aimed to evaluate the utility of risk stratification using ASA class for bariatric surgery patients and assessed predictive factors of postoperative complications.

The 2020 MBSAQIP database was analyzed, and an ASA-deemed high-risk cohort (class IV) and normal-risk (ASA class II and III) cohort were compared. Univariate analysis was performed to characterize differences between cohorts and to compare complication rates. Multivariate logistic regression analysis was performed to determine factors associated with increased odds of postoperative complications.

We evaluated 138 612 patients with 5380 (3.9%) considered high-risk and 133 232 (96.1%) normal-risk. High-risk patients were more likely to be older (46.2 ± 12.0vs.43.4 ± 11.9, p < 0.001), male (30.9%vs.18.4%, p < 0.001), have higher BMI (51.4 ± 10.2vs.44.9 ± 7.4, p < 0.001), and have more comorbidities. High-risk patients were more likely to have increased 30-day serious complications (4.5%vs.2.8%, p < 0.001) and death (0.2%vs.0.1%, p = 0.001) but not anastomotic leak (0.2%vs.0.2%, p = 0.983). Multivariate models showed ASA class IV patients were at higher odds for any serious complication by 30 days (aOR 1.36, 95%CI 1.18–1.56, p < 0.001) but not for death (aOR 1.04, 95%CI 0.49–2.21, p = 0.921). The factor independently associated with the highest odds of complication in both models was functional status preoperatively (partially dependent aOR 2.06, 95%CI 1.56–2.72, p < 0.001; fully dependent aOR 3.19, 95%CI 1.10–9.28, p = 0.033 for any serious complication; partially dependent aOR 5.08, 95%CI 2.16–12.00, p < 0.001 for death).

While elevated ASA class correlates with increased serious complications, pre-operative functional status appears to have a much greater contribution to odds of serious complications and mortality. These findings question the utility of using ASA to risk stratify patients peri-operatively and provides evidence for using a simpler and more practical functional status approach.

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