High Incidence of Impaired Glucose Regulation in Patients With no Known History of Diabetes Mellitus But With Hyperglycemia After Undergoing a Cardiac Surgical Procedure

Abstract

To determine the implications of the presence of hyperglycemia after a cardiac surgical procedure in patients with no history of diabetes mellitus (DM). We conducted a prospective study of 50 consecutive patients with no known history of DM who underwent a cardiac surgical procedure and had postoperative hyperglycemia (plasma glucose levels > or =110 mg/dL), requiring an insulin drip to achieve tight glucose control. These patients underwent a 2-hour oral glucose tolerance test (OGTT) at 6 weeks postoperatively to determine the percentage of subjects with impaired fasting glucose (IFG), impaired glucose tolerance (IGT), or type 2 DM. Of the 50 patients, 32 (64%) were found to have persistent glucose dysregulation. On the basis of OGTT results, 20% had IFG, 16% had both IFG and IGT, 10% had only IGT, and 18% had type 2 DM. Of the patients with newly diagnosed diabetes, 89% had a 6-week post-operative fasting plasma glucose (FPG) concentration of <126 mg/dL. There was a significant correlation between the preoperative FPG levels and the 6-week postoperative 2-hour OGTT glucose levels (P<.01). No correlation was found between the 6-week postoperative FPG levels and the 2-hour OGTT glucose levels (P = .26). Hyperglycemia after a cardiac surgical procedure implies a high risk of persistent glucose dysregulation. Preoperative FPG levels correlated better with 2-hour OGTT results than did the 6-week postoperative FPG values, but both were insensitive markers for diagnosing type 2 DM in these patients. In our cohort, hemoglobin A1c was not predictive of abnormalities of glucose metabolism. Our data support the need for performing a postoperative OGTT in patients with no known history of DM but the presence of hyperglycemia after a cardiac operation.