Body mass index predicts insulin sensitivity during cardiac surgery: a prospective observational study

Taking into account the previously described link between body weight and diabetes mellitus (DM) in non-surgical patients, and the understanding that the degree of intraoperative insulin resistance is a predictor of adverse clinical outcomes, we investigated the relationship between body mass index (BMI) and insulin sensitivity during cardiac surgery.

We prospectively enrolled 400 patients scheduled for elective cardiac surgery and divided them into groups based on the presence or absence of type-2 DM. They were further categorized into four subgroups based on their BMI: group 1- normal weight, BMI 18.5-24.9 kg·m^-2; group 2 - overweight, BMI 25-29.9 kg·m^-2; group 3 - obese, BMI 30-34.9 kg·m^-2; group 4 - morbidly obese, BMI ≥ 35 kg·m^-2. Insulin sensitivity was assessed using the hyperinsulinemic-normoglycemic clamp technique during surgery. We also analyzed the association of BMI, quality of postoperative glycemic control, and postoperative outcomes.

A linear negative relationship between BMI and insulin sensitivity (r = 0.42, P < 0.001) was observed, independent of the patients' diabetic state. There was also a positive correlation between BMI and postoperative glycemia (r = 0.30, P < 0.001) though the relationship between BMI and major and infectious complication was not significant (P = 0.56, P = 0.10, respectively).

Patient BMI may be used as a simple predictor of insulin sensitivity during cardiac surgery and as a predictor of the quality of postoperative glycemic control. A larger cohort will be necessary to evaluate the association of BMI, perioperative insulin resistance, and clinical outcomes.