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Surgical risk factors

Key risk factors for bariatric surgery

Six factors to help surgeons to predict, evaluate, reduce or avoid in-hospital mortality after weight loss surgery
Ninh T Nguyen

The top six risk factors that could help doctors and patients predict, evaluate, reduce or avoid in-hospital mortality after weight loss surgery, have been reported by investigators at University of California, Irvine, according to a study presented at the 28th Annual Meeting of the American Society for Metabolic & Bariatric Surgery (ASMBS) in Orlando, Florida.

The risk factors include the type of weight loss operation (gastric bypass or gastric band), surgical technique (open or laparoscopic), patient gender, type of insurance (private or Medicare), age and the presence of type 2 diabetes. 

“Bariatric surgery is safer than it has ever been, but there may be more we can do to make it even safer and improve the odds of survival for high risk patients,” said Dr Ninh T Nguyen, the study’s primary author and Chief of the Division of Gastrointestinal Surgery at UC Irvine Medical Center. “Doctors can use these risk factors to help in pre-operative planning and to help patients better understand his or her individual risk. One or more of these risk factors may increase the risk of death before discharge from the hospital.”

Study design

Nguyen and colleagues analysed hospital discharge data from the University HealthSystem Consortium (UHC) database where they identified 105,287 patients who underwent bariatric surgery between 2002 and 2009 at academic medical centres in the US. More than 80% of the patients were female and nearly three-quarters were caucasian. The investigators examined race, gender, age, the presence of comorbidities or diabetes, the technique of surgery, the type of operation and payer type. The type of operations included laparoscopic gastric bypass (45%), open gastric bypass (41%) and laparoscopic adjustable gastric banding (14%). 

For each top risk factor an adjusted odds ratio (AOR) was calculated using statistical analyses to determine its individual and relative impact on in-patient mortality. The higher the AOR, the greater the odds of it having an impact on patients. 

Outcomes

The study showed that overall in-hospital mortality rate was 0.17%, which was the primary outcome examined in the study. The death rate per 1,000 bariatric operations decreased from 4.0 in 2002 to 0.6 in 2009. In addition the investigators reported that showed a person who had an open, rather than a laparoscopic, weight loss operation faced nearly five times (AOR 4.8) the risk of in-hospital mortality. The AOR was 5.8 if the patient had a gastric bypass versus non-bypass patients, 3.2 if the patient was male, 3.0 if the patient had Medicare coverage rather than private insurance, 1.9 if the patient was age 60 or over and 1.6 if type 2 diabetes was present. 

“It’s important to remember that despite these risk factors, we are still talking about highly effective and safe operations that result in significant weight loss and improvement or resolution of obesity-related diseases. Morbid obesity itself is a major risk factor for premature death, and in fact may be riskier without intervention than the surgery itself,” said Nguyen. “The data shows laparoscopic bariatric surgery has become no riskier than gallbladder or hip replacement surgery.”

Previous studies have shown that the risks of living with morbid obesity outweigh of bariatric surgery and that patients may improve life expectancy by 89%  and reduce their risk of premature death by by 30 to 40%, after bariatric surgery.

Risk classification system

The investigators also identified a simple risk classification system that aims to predict individual patient risk of mortality. They suggest that clinicians can use the system to strategize a preoperative plan that may reduce surgical risk. In this bariatric mortality risk classification, patients can be grouped according to a score that is calculated based on the number of points assigned to their individual risk factors (I, II, III, or IV). The lowest risk group (class I) has an in-hospital mortality of 0.10% while the highest risk group (class IV) has a mortality of 0.70%. 

ASC paper

In a separate paper, presented at the Academic Surgical Congress in Huntington Beach, CA, in February 2011 and published in the journal Surgery, the same investigators from the University of California, Irvine, analysed data from the National Inpatient Sample database on patients with morbid obesity who underwent bariatric surgery from 2006 to 2008. The researchers performed multivariate logistic regression analyses to identify independent predictors of in-hospital mortality.

Results

A total 304,515 patients underwent bariatric surgery over the three year period. The majority of patients were female (80%) and caucasian (74%). Their mean age was 44 years and 31.6% were older than 50. The most common payer type was private (73.5%) and a laparoscopic approach was utilised in 86.2% of cases. The overall in-hospital mortality was 0.12%. Using multivariate regression analysis, male gender AOR, 1.7), age >50 years (AOR, 3.8), congestive heart failure (AOR, 9.5), peripheral vascular disease (AOR, 7.4), chronic renal failure (AOR, 2.7), open procedure (AOR, 5.5), and gastric bypass operation (AOR, 1.6) were factors associated with greater mortality. 

The investigators noted that ethnicity, hypertension, diabetes, liver disease, chronic lung disease, sleep apnoea, alcohol abuse, and payer type had no association with mortality in this study.

Conclusion

“Modifiable risk factors predictive of mortality include open surgery and gastric bypass procedure, whilst non modifiable risk factors include older age, male gender, and a history of congestive heart failure, peripheral vascular disease, and chronic renal failure,” said the authors.“Surgeons should consider these factors in selection of patients to undergo bariatric operations, providing informed consent, and selection of the procedural type.”

Effective

Bariatric surgery has been shown to be the most effective and long lasting treatment for morbid obesity and many related conditions. The Agency for Healthcare Research and Quality has reported significant improvements in the safety of bariatric surgery due in large part to improved laparoscopic techniques and the advent of bariatric surgical centres of excellence. The overall risk of death from bariatric surgery is about 0.1% and the risk of major complications is about 4%.

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