Relationship between nadir hematocrit during cardiopulmonary bypass and postoperative hyperglycemia in nondiabetic patients.

Background: Hyperglycemia is common after cardiac surgery in both diabetic and nondiabetic patients and is associated with increased morbidity and mortality. Association between nadir hematocrit levels on cardiopulmonary bypass (CPB) and postoperative hyperglycemia is not clear. This study was carried out to determine the relationship between nadir hematocrit during CPB and postoperative hyperglycemia in nondiabetic patients.

Methods: Records of 200 nondiabetic patients undergoing coronary artery bypass grafting operation were retrospectively reviewed. In the first analysis, patients were divided into two subgroups according to the presence or absence of hyperglycemia. Further analysis was made after dividing the patients into 3 subgroups according to nadir hematocrit levels on CPB (less than 20%; 20% to 25%; greater than or equal to 25%).

Results: Compared to patients without hyperglycemia, patients with postoperative hyperglycemia had significantly lower preoperative hematocrit levels (p = 0.004) and were associated with lower nadir hematocrit levels during CPB (p= 0.002). Peak intensive care unit blood glucose levels and number of blood transfusions were significantly higher in patients with nadir hematocrit levels less than 20. (p<0.001 and p<0.001 respectively). Logistic regression analysis demonstrated that nadir hematocrit levels less than 20% (OR 2.9, p=0.009) and allogenic blood transfusion (OR 1.5, p=0.003) were independently associated with postoperative hyperglycemia.

Conclusions: Nadir hematocrit levels on CPB less than 20% and allogenic blood transfusions were independently associated with postoperative hyperglycemia in nondiabetic patients. Patients with a nadir hematocrit levels less than 20 % during CPB should be closely monitored for hyperglycemia in the perioperative period.