Simply being obese does not increase the risk of dying after noncardiac surgery. However, a new study found that extremely obese patients who also had hypertension and diabetes had double the risk of dying after undergoing noncardiac surgery than normal-weight patients. Out of 310,208 patients who had noncardiac surgery during the study period, 20,845 (6.7 percent) had modified metabolic syndrome (mMetS—obesity, hypertension, and diabetes). Most of these patients (62.8 percent) were obese (30 to 39.9 kg/m2), another 25.7 percent were morbidly obese (40 to 49.9 kg/m2), and 11.5 percent were super obese (>50 kg/m2). In contrast, 98,036 patients were obese, morbidly obese, or super obese, but did not meet the other mMetS criteria.
Patients with mMetS and super obesity had a significant, twofold increased risk of death within 30 days after surgery compared with normal-weight patients (18.5 to 24.9 kg/m2). Patients with mMetS were two to three times more likely to have heart complications, and three to seven times more likely to have acute kidney injury, than normal-weight patients.
The researchers based this retrospective study on data on 310,208 patients in the American College of Surgeons National Surgical Quality Improvement Program database, who underwent general, vascular, or orthopedic surgery between 2005 and 2007. Because the database did not include information on glucose tolerance or waist circumference, which constitute part of the formal definition of mMetS, the researchers used a body mass index (BMI) of 30 kg/m2 or higher (obesity), treatment with an oral hypoglycemic drug or insulin (indicating diabetes), and hypertension to define mMetS. The study was funded in part by the Agency for Healthcare Research and Quality (HS16737).
More details are in "Perioperative outcomes among patients with the modified metabolic syndrome who are undergoing noncardiac surgery," by Laurent G. Glance, M.D., Richard Wissler, M.D., Dana B. Mukamel, Ph.D., and others in the October 2010 Anesthesiology 113(4); pp. 859-872.