New scoring system predicts gastric bypass surgery risk
Duke University Medical Center surgeons have developed a simple scoring system based on five patient characteristics that can predict which candidates for gastric bypass surgery would be at highest risk for dying.
If validated by additional prospective studies, the new scoring system not only would give surgeons concrete information on which to base treatment options, but would help patients make informed decisions about potential risks, its developers said. Additionally, the system, if widely adopted, could provide a standardised way to compare outcomes among centers that perform the surgery.
Gastric bypass 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 they feel satisfied much faster.
Gastric bypass surgery is generally safe, according to the Duke researchers. But as with any type of surgery, there is a risk of adverse side effects or even death. The key, they said, is determining which patients are at the lowest risk.
"Currently, there is no clinically useful system to help determine which patients would be at highest risk of dying after gastric bypass surgery," said Eric DeMaria, M.D., director of bariatric surgery at Duke, who reported on the new scoring system June 29, 2006, at the annual meeting of the American Society for Bariatric Surgery in San Francisco.
"We developed a scoring system that is based on five easy-to-identify patient characteristics that can help us decide whether or not a specific patient is a good candidate for surgery and what the probable risks would be," DeMaria said. "When talking to patients, we can cite national averages on risks, but that is not very helpful when I have a specific patient sitting in front of me. We needed a scientifically valid way for assessing individual risk."
Roughly 170,000 Americans underwent gastric bypass surgery in 2005, according to the American Society for Bariatric Surgery. The society estimates that 15 million people, or 2 percent of the nation's population, are morbidly obese.
To create their scoring system, the researchers retrospectively analysed the outcomes of all 2,075 patients who underwent gastric bypass surgery between 1995 and 2004 at Virginia Commonwealth University, where DeMaria was a bariatric surgeon before coming to Duke in 2005. Both universities provided support for the current study.
The researchers found that 31 of patients (1.5 percent) died within 90 days of surgery. In analysing those who died, DeMaria and colleagues identified four factors that were independently predictive of increased risk:
- A body mass index of greater than 50. This measure takes into account the relationship of weight and height; it is calculated by dividing weight in kilograms by height in meters squared. A range of 18.5 to 25 is considered normal.
- Male gender. Men are more likely than women to suffer from conditions such as hypertension, diabetes and metabolic disorder, which can add to the risks of surgery.
- Hypertension. Patients with hypertension typically have heart disease or chronic inflammation of blood vessels, which might add to the risks of surgery.
- Pulmonary embolus risk. This variable measures whether patients have had a previous pulmonary embolism or are at risk for developing one. A pulmonary embolism is a blood clot that usually forms in a blood vessel deep in the thigh and travels up to the lung, where it can block blood flow to the lungs.
- Increased age. In addition to the above four characteristics that were identified by the analysis of the 2,075 patients, the researchers added a fifth factor – age -- to their scoring system. Based on the results of past studies, patients over the age of 45 are known to be at the highest risk for death after bariatric surgery.
"In using our system, each one of the five characteristics is worth one point," DeMaria explained. "Those patients with a score of zero are at the least risk, while those with five points are at the highest risk."
The system deems patients with a score of zero or one to be low-risk. In the study, only three of the 957 patients in this group died, for a mortality rate of 0.31 percent. None of the 356 patients with zero points died. The medium-risk group, with a score of two or three points, had a mortality rate of 1.91 percent (19 deaths out of 999 patients). The high-risk group, with a score of four or five points, had a mortality rate of 7.56 percent (nine deaths out of 119 patients).
"Many people see gastric bypass surgery as an option to use only when all other approaches to weight loss have failed," DeMaria said. "However, our system shows that this strategy may need to be reconsidered. If patients put off surgery while they attempt other 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.
"Our findings show that for the low-risk group of patients, gastric bypass surgery is a very safe option," DeMaria continued. "For those patients in the highest risk category, we should look at performing lower-risk or a number of smaller procedures to reduce the potential risk."