Economies of scale: body mass index and costs of cardiac surgery in Ontario, Canada

Abstract

An obesity paradox has been described, whereby obese patients have better health outcomes than normal weight patients in certain clinical situations, including cardiac surgery. However, the relationship between body mass index (BMI) and resource utilization and costs in patients undergoing coronary artery bypass graft (CABG) surgery is largely unknown. We examined resource utilization and cost data for 53,224 patients undergoing CABG in Ontario, Canada over a 10-year period between 2002 and 2011. Data for costs during hospital admission and for a 1-year follow-up period were derived from the Institute for Clinical Evaluative Sciences, and analyzed according to pre-defined BMI categories using analysis of variance and multivariate models. BMI independently influenced healthcare costs. Underweight patients had the highest per patient costs ($50,124 ± $36,495), with the next highest costs incurred by morbidly obese ($43,770 ± $31,747) and normal weight patients ($42,564 ± $30,630). Obese and overweight patients had the lowest per patient costs ($40,760 ± $30,664 and $39,960 ± $25,422, respectively). Conversely, at the population level, overweight and obese patients were responsible for the highest total yearly population costs to the healthcare system ($92 million and $50 million, respectively, compared to $4.2 million for underweight patients). This is most likely due to the high proportion of CABG patients falling into the overweight and obese BMI groups. In the future, preoperative risk stratification and preparation based on BMI may assist in reducing surgical costs, and may inform health policy measures aimed at the management of weight extremes in the population.

Implications of obesity in cardiac surgery: pattern of referral, physiopathology, complications, prognosis

“…Similar evidence derived from valvular and combined surgery (4). Obese patients require significantly lower rates of re-exploration for bleeding and allogenic blood products transfusions, which are, in turn, major determinants of lung impairment (13,15). Data from a multi-institutional perfusion database demonstrated, that a BMI in obese I category was associated with a 9.9% decrease in transfusion risk (P<0.05).…”

“…On mere clinical ground, the risk of postoperative hypoxia (as reflected by a low PaO 2 /FIO 2 ) almost doubles for each increase in BMI class. Nevertheless, only the morbidly obese, a fairy small proportion of cardiac surgery recipients, experience an increased risk of prolonged ventilation, reintubation, pulmonary infections, intensive care recidivism and prolonged process of care (13).…”

“…Conventional wisdom suggests that obesity is associated with higher postoperative infectious complications prolonged ICU stay and exponential resource utilization (2,13). Superficial and deep sternal as well as harvest site wound infections are known to plague the postoperative course of this patients' subset (23).…”

“…Similarly, higher rates of ICU acquired urinary tract, pulmonary, catheter and blood-stream infections have been reported in the highest BMI classes with a net increase in the incidence of sepsis. Intriguingly despite this higher vulnerability, reported overall mortality rates as well as the death rates for septic shock are inferior (2,13,24). The preserved or increased lean body mass and better nutritional status related to higher BMI imply a sufficient nutritional reserve, a more efficient metabolic state and a better inflammatory and immune response to surgery, which account for this protective effect once obesity-induced infectious complication may develop.…”

“…These studies showed also that surgical risk scoring systems such as the EuroSCORE have no statistical correlation with BMI and are poor predictors of the length of the process of care (2,4). Such evidences prompted the concept that both underweight and morbid obese should be considered preoperatively rather than reactively and, when referred for elective surgery, should undergo a focused metabolic status management, and a thorough evaluation of health status (13,23). Table 1 Interaction between obesity physiologic derangements and cardiac surgical procedure on early complications (for each target organ are reported the alterations induced by obesity, the burden of the surgical procedure, and the clinical outcome) Target Obesity in the heart transplant recipient: from candidacy to long-term survival Heart failure patients are an increasingly common demographic in cardiac surgical theatres.…”