Evaluation of patients prior to bariatric surgery is largely a matter of common sense. The goal is to identify any problems that are able to be modified with non-surgical intervention, and to introduce treatment to reduce risk. As I explain to patients, the fitter they are prior to surgery the less likely they are to get really crook if they encounter unforeseen complications, and the better they will do afterwards when it comes to getting on their feet and losing weight. However, for most patients the good stuff really happens post-operatively. Diabetes resolves, hypertension improves, sleep apnoea is cured…. For that reason, we really want to identify and treat only those problems which will significantly increase the risks of surgery. All other problems should be addressed after surgery. For example, diabetic control preoperatively does not need to made perfect, as it almost universally improves dramatically after surgery.
Guidelines as to whom we should consider suitable for bariatric surgery were introduced nearly 20 years ago – and have not altered since. Now there’s a situation that has to change with the times! In any case, the National Institutes of Health in the US came up with the following recommendations:
Bariatric surgery should be considered in individuals with:
- BMI of 40kg/m2 or greater
- BMI of 35 to 39kg/m2 with severe comorbid conditions such as life- threatening cardiopulmonary problems or diabetes.
- BMI of 35 to 39kg/m2 with obesity-induced physical problems interfering with lifestyle (e.g joint disease which is treatable but for the obesity)
- No underlying endocrine abnormality that can contribute to obesity, ongoing substance abuse or uncontrolled psychiatric disturbance
- An ability to understand the surgery and its consequences and comply with post-operative dietary modification
- No illness that greatly reduces life expectancy
In our clinical evaluation of patients preoperatively we want to ensure that there is no undiagnosed cardiac, respiratory or endocrine disease that will significantly increase the risk of perioperative complications. The population of patients undergoing bariatric surgery is at particular risk of coronary artery disease, cardiomyopathy, uncontrolled hypertension, hypothyroidism, obstructive sleep apnoea or obesity hypoventilation syndrome, asthma or chronic obstructive pulmonary disease or undiagnosed diabetes. Not every patient will require the same specific workup. However, investigation which we frequently request include exercise testing, echocardiography, lung function tests and diagnostic sleep studies. Everybody has blood tests, including coagulation studies, iron studies, blood glucose and thyroid function, lipid studies and full blood count as well as an ECG. (Most of our patients have had these investigations requested by their general practitioners).
In 2007, a useful clinical risk-stratification tool was suggested by DeMaria and colleagues in a paper published in the journal of Surgery for Obesity Related Disease. This score reminds us that mortality rates are generally very low for bariatric surgery, but are significant in some patient groups.
The score takes into account the following variables:
- BMI >50
- Male gender
- History of hypertension
- Increased risk for pulmonary embolism ( variable included previous PE, inferior vena cava filter, right heart failure, obesity hypoventilation syndrome)
- Age 45 years of more
One point is awarded for each variable, with mortality rates as follows:
- score 0-1, mortality rate 0.31%
- score 2-3, mortality rate 1.90%
- score 4-5, mortality rate 7.56%
This scoring system was, however, created from one particular retrospective analysis in one institution and validated in another institution. The PE risk variable is not straight forward, and less than 1% of patients scored all 5 points. The operation involved was gastric bypass, which is a much more complicated procedure than gastric banding or vertical gastroplasty, which are the major procedures performed in Hamilton.
A much bigger study of qualified surgeons in the US, which was published in the New England Journal of Medicine last year and which included gastric bands, showed very low mortality rates, as per the attached table. In that study, only very high BMI, history of pulmonary embolism, and perhaps history of OSA, were associated with increased risk of mortality.
A study published in the NEJM in 2007 suggested that long-term mortality in very obese patients was reduced by 40% in patients who had gastric-bypass surgery. The slightly – increased risk of dieing post-operatively should, perhaps, be considered in light of that sobering, dramatic statistic.
Andrew
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