Influence of Obesity on Complications and Costs Following Intestinal Surgery

Wakefield H, Vaughan-Sarrazin MS, Cullen J. Influence of Obesity on Complications and Costs Following Intestinal Surgery. Paper presented at: VA Association of Surgeons Annual Meeting; 2011 Apr 11; Irvine, CA.

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• IIR 07-151 – The Business Case for Reduction in Surgical Complication Rates in the VA

Background: Obesity is a risk factor for many comorbidities which increase the cost of health care. We sought to examine the effect of obesity on surgical complications and cost in a group of patients undergoing intestinal surgery. Methods: Using Veterans Affairs Surgical Quality Improvement Program (VASQIP), which includes clinical data abstracted from medical records for VA surgical patients and the VA Decision Support System (DSS), which provides the costs of individual patient encounters on the basis of relative values assigned to intermediate products, we examined surgical complications and costs of care in 4,881 patients undergoing intestinal surgery during fiscal year 2006. Patients were classified into four groups based on BMI: malnourished (less than 18), normal weight (18-30), obesity class I-II (30-40), and obesity class III (greater than 40). Patient endpoints included the occurrence of any complication, and specifically wound and respiratory complications, as well as surgical costs incurred within 30 days of surgery. Endpoints were compared across the four BMI categories in unadjusted analyses and analyses that controlled for pre-operative patient risk factors (e.g., demographics, co-morbidities, functional status, preoperative laboratory values), and hospital-level variation using multivariable models. Models were estimated as generalized linear regression models with a a logit link and binary distributed errors for complications, and with a log link and gamma distributed errors for surgical costs. Results: Overall 69% of patients were categorized as having normal BMI, while 2%, 25%, and 3% were malnourished, obesity class I-II, and obesity class III, respectively. Of the four categories, patients in obesity class III were most likely to have any complication (29 %, 29%, 31%, and 38% for normal, malnourished, class I-II, or class III, respectively). Similarly, wound complications were most common in heavier patients (12.4% of normal patients vs 17.4% and 21.2% for obesity class I-II or obesity class III, respectively.), and there were also more respiratory complications in class III patients (17.6%) compared to normal patients (12.5%). After controlling for patient risk factors and hospital-level variation, patients in obesity class I-II were still 1.21 times more likely to have any complication and patients in obesity class III were 1.41 times more likely to have any complication when compared to normal patients. Similarly, patients in obesity class I-II were 1.48 times more likely to develop a wound complication compared to normal patients, and patients in class III were 1.94 times as likely to develop a wound complication, and 1.5 times as likely to develop a respiratory complication, compared to normal patients. In contrast, costs were greatest for malnourished patients at $45k compared to normal patients at $37k. However, after controlling for patient risk factors and variation in costs attributable to the admitting hospital, there were no significant cost differences between the four BMI categories. Conclusions: Obesity leads to increased wound and respiratory complications in intestinal surgery. Nevertheless, obesity alone is not an independent risk factor for increased costs in intestinal surgery.