Hyperglycemia during cardiopulmonary bypass is an independent risk factor for mortality in patients undergoing cardiac surgery

Abstract

Background: Hyperglycemia is commonly present in the perioperative period in patients undergoing cardiac surgery, even during administration of insulin. A direct relationship between postoperative hyperglycemia and mortality has been established in diabetic patients undergoing cardiac surgery. However, this relationship might be confounded because patients with poor outcome receive more glucogenic drugs postoperatively. We assessed the influence of hyperglycemia (highest glucose level) during cardiopulmonary bypass on perioperative morbidity and mortality in diabetic and nondiabetic patients.

Methods: We performed a multivariate logistic regression analysis on all diabetic (n = 1579) and nondiabetic (n = 4701) patients undergoing cardiac surgery at the Toronto General Hospital between 1999 and 2001. Boluses of insulin were given during cardiopulmonary bypass when the glucose level exceeded 15 mmol/L, when the serum potassium level exceeded 6.0 mmol/L, or both.

Results: Overall mortality was 1.8% (n = 115). A high glucose level during cardiopulmonary bypass was an independent predictor of mortality in both diabetic (odds ratio, 1.20; confidence interval, 1.08-1.32) and nondiabetic (odds ratio, 1.12; confidence interval, 1.06-1.19; per millimole per liter increase in glucose) patients. A high glucose level during cardiopulmonary bypass was also an independent predictor of all major adverse events in both patient groups (odds ratio, 1.06; confidence interval, 1.03-1.09). A high glucose level was not closely related to cardiopulmonary bypass (r = 0.3) or aortic crossclamp times (r = 0.4).

Conclusions: A high peak serum glucose level during cardiopulmonary bypass is an independent risk factor for death and morbidity in diabetic patients and unexpectedly also in nondiabetic patients.