Surgery Outcomes Better with Higher BMI

Surgical patients with a body mass index (BMI) at the lower end of the normal range were more likely to die within 30 days of the procedure than those in the moderately overweight range, according to a new study.

Researchers at the University of Virginia (Charlottesville, USA) conducted a multivariable logistic regression analysis of 189,533 surgeries performed in 2005 and 2006, which were recorded in the US National Surgical Quality Improvement Program (NSQIP) database. The researchers wished to assess the statistical significance of the relationship between BMI and mortality, with adjustments for patient-level differences in overall mortality risk and principal operating procedures. A separate multivariable logistic regression model was developed to assess the significance of the interaction between BMI and primary procedure.

The results showed that among 3,245 patients that died within 30 days of their surgery (1.7%), those with a BMI of less than 23.1 demonstrated a significant increased risk of death, with 40% higher odds compared to patients in the middle range for BMI (26.3 to 29.7). Evaluation of 30-day mortality odds ratios for 45 individual types of surgeries--with laparoscopy as the reference--ranged from 0.03 for breast lumpectomy to 2.47 for noncardiac vascular bypass and shunt procedures, before accounting for BMI. The researchers also found that mortality increased linearly to BMI in some procedures, relative to laparoscopy. These included ileostomies and other enterostomies, musculoskeletal procedures, and mastectomies, among other procedures. The study was published in the November 21, 2011, issue of the Archives of Surgery.

“Body mass index is a significant predictor of mortality within 30 days of surgery, even after adjusting for the contribution to mortality risk made by type of surgery and for a specific patient's overall expected risk of death,” concluded lead author George Stukenborg, PhD, and colleagues. “These individual types of procedures include procedures with which the general surgeon should have definite experience; colorectal resection, colostomy formation, cholecystectomy, hernia repair, mastectomy, and wound debridement.”

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