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DURHAM, N.C. -- A simple scoring system based on five medical factors accurately predicts which patients being considered for gastric bypass surgery would be at highest risk of dying.

The scoring system, which was first proposed last year by Duke University Medical Center surgeons, has been validated in a new study of more than 4,400 patients. The system takes into account a patient's weight, gender, age, blood pressure and risk of developing a blood clot in the lungs.

Physicians using the system can easily determine if their patients' risk of dying from the surgery is low, medium or high. The new analysis found that patients in the high-risk group were six times more likely to die than those in the low-risk group, and patients in the medium-risk group were three times more likely to die.

Gastric bypass surgery, also known bariatric surgery, is used to help people who are morbidly obese lose weight. Although the surgery has several variants, the basic procedure involves stapling off a large portion of the stomach and reattaching the intestine to the smaller remaining portion. Because of their decreased stomach capacity, patients are unable to eat as much food and feel sated much faster.

"This represents the first validated scoring system for assessing risk for patients considering bariatric surgery," said Duke surgeon Eric DeMaria, M.D., who developed the system. "The system gives surgeons concrete data they can use in surgical decision-making and in their discussions with patients. Also, the system provides standardization of surgical outcomes, making comparisons among centers more meaningful."

DeMaria presented results of the new study April 26, 2007, at the annual meeting of the American Surgical Association, in Colorado Springs, Colo.

Roughly 170,000 Americans underwent gastric bypass surgery in 2005, according to the American Society for Bariatric Surgery.

The new study examined data on 4,433 patients who underwent bariatric surgery at the University of South Florida, the Medical University of South Carolina and a private practice in Scottsdale, Ariz.

Of the 2,166 patients classified by the scoring system as being in the low-risk group, eight died. Twenty-six of the 2,142 patients in the medium-risk group died, and three of the 125 patients in the high-risk group died. While patients in the high-risk group represented less than 3 percent of the total, they accounted for 8 percent of the deaths.

In the scoring system, patients with none or one of the five medical factors are considered low-risk; those with two or three factors are considered medium-risk; and those with four or five factors are considered to be at the highest risk.

The factors are:

  • A body mass index of greater than 50. On this scale, a measure of body fat based on a person's weight and height, a level of 30 and above is considered obese.
  • Male gender. Men are more likely than women to suffer from conditions such as hypertension, diabetes and metabolic disorder that can add to the risks of surgery.
  • Increased age. Patients over 45 are known to be at the highest risk for death after bariatric surgery.
  • Hypertension. Patients with hypertension, or high blood pressure, typically have heart disease or chronic inflammation of blood vessels that can add to the risks of surgery.
  • Pulmonary embolus risk. Patients who have had a pulmonary embolism, a blood clot in the lungs, or are at risk for developing an embolism are at elevated risk.

"When talking to patients about bariatric surgery, we can cite national averages on risks, but that is not very helpful when I have a specific patient sitting in front of me," DeMaria said. "Many physicians and patients see bariatric surgery as an option to use only when all other approaches to weight loss have failed. However, our system shows that this strategy may need to be reconsidered.

"If patients put off surgery while they attempt other weight-loss therapies that ultimately don't work, over time they risk moving into a higher-risk category as they gain more weight, get older or develop hypertension. In these cases, delays can make surgery even riskier," DeMaria said.

For patients at highest risk, DeMaria said, the best approach may be for them to spend some time losing weight before the surgery. Alternatively, surgeons could perform a series of smaller, and therefore less risky, procedures over time.