Vascular Surgery Outcomes Differ by Obesity Classification

SAN DIEGO — Underweight patients have poorer overall outcomes in vascular surgery, yet morbidly obese patients have increased morbidity, primarily due to wound infections, renal complications, and thromboembolic complications, results from a multicenter analysis showed.

“There are no large studies on the effect of obesity on vascular surgery,” Dr. Eleftherios S. Xenos said at the Vascular Annual Meeting. “There is some agreement that wound infection tends to be higher in obese patients, but in terms of mortality there has not been a definite answer.”

Dr. Xenos and his associates queried the Patient Safety in Surgery Study Database for a sample of major vascular procedures performed at 14 academic medical centers in the United States between 2002 and 2004. They obtained data on 7,543 vascular surgery patients that included the National Surgical Quality Improvement Program (NSQIP) clinical definitions of patient risk factors and 30-day outcomes.

Of the 7,543 patients, 4.6% were underweight (body mass index [BMI] of less than 18.5 kg/m

Vascular procedures performed included lower extremity revascularization (24.5%), aneurysm repair (17.4%), cerebrovascular procedures (17.3%), amputations (9.4%), and “other” (31.4%). Within 30 days after surgery, 1,659 patients (22%) developed complications and 295 (3.9%) died.

As expected, risk factors for hypertension and diabetes increased with increasing BMI. However, rates of smoking, stroke, and recent weight loss—defined as more than 10% of body weight—decreased as BMI increased.

The top three NSQIP predictors of vascular surgery mortality were presence of preoperative sepsis, American Society of Anesthesiologists' physical status classification, and functional dependence. “For these three risk factors, the overweight and obese I patients had the least amount of risk, with the highest risk in the underweight category,” Dr. Xenos said.

“The overweight and obese I category patients had a significantly higher albumin level, as compared with normal class patients,” Dr. Xenos reported.

The distribution of major complications among patients was U-shaped, with a higher incidence of complications among underweight patients and the lowest among the normal weight, overweight, and obese I category patients.

Obese II and obese III category patients had a significantly higher incidence of wound infections and renal and urinary tract infection complications, while morbidly obese patients had a significantly higher incidence of thromboembolic complications.

After the researchers adjusted for age, gender, and type of operation, the 30-day mortality risk was lowest among the obese I patients (OR 0.53) and highest among the underweight patients (OR 1.48).

“Mild obesity may have an independent protective effect on nutrition, metabolic status, and improved cardiac performance,” said Dr. Xenos, who had no conflicts to disclose.

'Mild obesity may have an independent protective effect.' DR. XENOS