Risk Score Accurately Predicts Mortality After Bariatric Surgery

Laurie Barclay, MD

May 02, 2007

May 2, 2007 — The Obesity Surgery Mortality Risk Score (OS-MRS), a simple scoring system based on 5 medical factors, accurately predicts which patients being considered for gastric bypass surgery (GBS) for morbid obesity would be at highest risk for dying, according to the results of a multicenter study presented at the American Surgical Association annual meeting in Colorado Springs, Colorado.

"We know that the risk of bariatric surgery is very low overall, but not many studies have been done to stratify that risk," presenter and lead author Eric DeMaria, MD, a professor of general surgery at Duke University Medical Center in Durham, North Carolina, told Medscape. "This is the first study we know of that has independently validated a risk stratification system for bariatric surgery."

The OS-MRS was originally developed from a single institution, but it was not previously validated at different institutions. This scoring system assigns 1 point to each of 5 preoperative factors, including body mass index (BMI) higher than 50 kg/m 2, male sex, hypertension, risk for pulmonary embolism, and age older than 45 years. Lowest risk (class A) is a score of 0 to 1, intermediate risk (class B) is a score of 2 to 3, and high risk (class C) is a score of 4 to 5.

In a validation cohort of 4433 consecutive patients undergoing GBS at the University of South Florida, the Medical University of South Carolina, and a private practice in Scottsdale, Arizona, overall mortality was less than 1%, and the risk for surgical mortality in the low-risk group was about 0.3%. There were only 6 patients who had all 5 risk factors.

Mortality in classes A, B, and C was statistically different from each of the other 2 classes (P <  .05), with mortality 3-fold greater in class B than in class A, and mortality 6-fold greater in class C  than in class A. Although class C patients made up only 3% of the total cohort (n = 125), they accounted for a disproportionate 8% of all mortalities.

"The mortality risk of a bariatric procedure is highly dependent on the patient and on the risk factors the patient brings to the operating table," Philip Schauer, MD, president of the American Society for Bariatric Surgery, told Medscape. Dr. Schauer was not involved in this study but was asked to provide independent commentary.

"Five major risk factors predict mortality: increased age, especially after age 45; increased BMI; male gender; risk factors for pulmonary thrombosis; and comorbid conditions," Dr. Schauer said. "This is not earth-shattering news, but the contribution of this study is developing this score to allow patients and doctors to develop prognosticators of surgery risk."

According to Dr. Schauer, who is also director of the Bariatric and Metabolic Institute at the Cleveland Clinic in Ohio, limitations of this study include insufficient statistical power to identify other predictors such as cirrhosis, despite the large sample size.

"The risk of surgery increases with the duration of morbid obesity, so patients who suffer from this often lifelong condition should not delay the only intervention known to help, namely bariatric surgery," Dr. DeMaria said. "The risk of surgery also increases with BMI, so weight reduction strategies are possible interventions that may reduce risk. Some of these strategies may be surgical, for example, staged surgical procedures that assist with weight loss before definitive surgery is done."

Other preoperative strategies that may help minimize risk, according to Dr. Schauer, include optimizing blood pressure control.

"Even for patients who are at higher risk for mortality from surgery than are other patients, surgery may still be the best option, because the mortality risk of severe obesity is much higher than that of the surgery," Dr. Schauer concluded. "Most studies show that by 5 to 7 years after bariatric surgery, mortality risk declines by 50% to 70%, so it's a very good tradeoff."

Dr. DeMaria's group is planning a prospective assessment of the validity of their scoring system, using data collected from approximately 100,000 patients per year through the American Society for Bariatric Surgery.

"OS-MRS is the first validated risk scoring system in bariatric surgery and is anticipated to aid informed consent, assist surgical decision-making, and allow standardization of outcome comparisons between centers," the authors conclude.

Drs. DeMaria and Schauer report no relevant financial relationships directly related to this topic.

American Surgical Association 2007 Annual Meeting. Presented April 26, 2007.

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