Proposal for a bariatric mortality risk classification system for patients undergoing bariatric surgery

Abstract

Background: An obesity surgery mortality risk score derived from a single clinical series can be used to stratify the mortality risk of patients undergoing gastric bypass. However, such a scoring system does not take into account 2 important factors in contemporary bariatric surgery--increased use of the laparoscopic approach and laparoscopic adjustable gastric banding. The present study analyzed the preoperative factors that might predict in-hospital mortality after bariatric surgery using data from academic medical centers and proposes a classification system for predicting mortality.

Methods: Using the "International Classification of Diseases, 9th revision," diagnosis and procedural codes, the data for all patients who underwent bariatric surgery for the treatment of morbid obesity from 2002 to 2009 were obtained from the University HealthSystem Consortium database. The limitations of this database included the lack of the body mass index and the underestimation of some co-morbidities, such as sleep apnea. Multiple regression analyses were performed to determine the factors predictive of greater in-hospital mortality. The factors examined included race, gender, age, co-morbidities, surgical technique (laparoscopic versus open), bariatric operation (gastric bypass versus nongastric bypass), and payer type. A scoring system was devised by assigning 1 point for each major factor (those with an adjusted odds ratio [AOR] of ≥2.0) and .5 point for each minor factor (those with an AOR <2.0). Using contemporary data from 2007 to 2009, the in-hospital mortality was analyzed according to the classification: class I, 0-0.5 point; class II, 1.0-1.5 points; class III, 2.0-3.0 points; and class IV, ≥3.5 points.

Results: During the 8-year period, 105,287 patients underwent bariatric surgery. The operations included laparoscopic gastric bypass (45%), open gastric bypass (41%), and laparoscopic gastric banding or gastroplasty (14%). The overall in-hospital mortality rate was .17%. The number of deaths per 1000 bariatric operations decreased from 4.0 in 2002 to .6 in 2009. Using regression analyses, the factors predictive of greater in-hospital mortality were male gender (AOR 3.2), gastric bypass procedure (AOR 5.8), open surgical technique (AOR 4.8), Medicare payer (AOR 3.0), diabetes (AOR 1.6), and age >60 years (AOR 1.9). The mortality rate was .10% for class I patients, .15% for class II, .33% for class III, and .70% for class IV (P < .05 among all classes).

Conclusion: Within the context of academic centers, the mortality after bariatric surgery has decreased substantially since 2002, with an increase in the use of the laparoscopic technique and laparoscopic gastric banding. A bariatric mortality risk classification system was developed to stratify mortality, given the limits of this database, which does not include the body mass index and underestimates the incidence of sleep apnea. It might be useful to aid surgeons in surgical decision-making, to inform patients of their risks, and for quality improvement reporting purposes.