In 2010, 27 per cent of Australia’s 22 million population were obese, with the number continuing to rise. The mean BMI has increased over the last 30 years from 24 to 28 kg. Many studies have shown that obesity is associated with lower mortality after non-cardiac and cardiac surgery. The “obesity paradox” is surprising given the evidence that obesity is associated with decreased life expectancy. These inconsistent and controversial results may be due to the existence of two distinct subgroups. One group is “the metabolically healthy but obese,” whereas the other group are the “metabolically obese.” These are the patients with the metabolic syndrome. The metabolic syndrome is characterized by central obesity, hypertension, impaired glucose tolerance, dyslipidemia, and prothrombotic and proinflammatory states. When grouped together these metabolic abnormalities are associated with an increased risk of cardiovascular disease, diabetes and overall mortality.

A recent meta-analysis demonstrated that the metabolic syndrome is associated with a 35 per cent increase in the risk of all-cause mortality, a 50 per cent increase in the risk of cardiovascular disease, and a 75 per cent increase in the risk of stroke. Patients with the metabolic syndrome also have a six-fold increased risk of chronic kidney disease9 and are more likely to have impaired lung function.

In a large database review, 11 patients with the modified metabolic syndrome (obesity, hypertension, treated diabetes) undergoing non-cardiac surgery were found to be at increased risk for mortality, cardiac adverse events, pulmonary complications, acute kidney injury, stroke and coma, wound complications, and postoperative sepsis. Increasing levels of obesity in patients with the modified metabolic syndrome was generally associated with worse postoperative outcomes. The magnitude of the increase in risk was dramatic for some complications. In particular, compared with normal-weight patients, patients with the modified metabolic syndrome had a nearly 2- to 3-fold higher risk of cardiac complications, a 1.5 - to 2.5-fold higher risk of pulmonary complications, a 2-fold higher risk of coma and stroke, and a nearly 3- to 7-fold higher risk of acute kidney injury. Recent studies have also shown increased operative mortality, stroke, and acute renal failure in patients with the metabolic syndrome undergoing coronary artery bypass grafting.

Implications for surgeons

Surgeons need to have an awareness of the increased risks in performing non-bariatric surgery in obese patients especially those with the additional features of metabolic syndrome. This should include an awareness of the organ systems particularly at risk and the employment of strategies to attempt to reduce the risks. These strategies will commonly involve the anaesthetist and relevant physicians in the preoperative and postoperative phases, as well as equipment and facility factors.

Read the complete position paper at the link below.