Evaluation of outcomes and complications in patients who experience hypoglycemia after cardiac surgery

Objective: The objective of the study was to elucidate 30-day and long-term outcomes in patients experiencing postoperative hypoglycemia. Methods: We conducted a retrospective review of patients who underwent cardiac surgery between September 4, 2007, and April 30, 2011, at Northwestern Memorial Hospital who had intensive treatment of hyperglycemia postoperatively. Of 1,325 patients, 215 experienced a hypoglycemic episode (blood glucose <70 mg/dL) within the first 3 postoperative days. A total of 198 were propensity-score (PS) matched to 363 patients without hypoglycemia. The analysis consisted of a comparison of 30-day cardiac outcomes and long-term mortality between those who experienced a hypoglycemic event and those who did not. Results: Between patients who experienced hypoglycemia compared to those that did not, there were no significant differences in mean glucose values while on insulin drips (119.8 ± 33.5 mg/dL vs. 120.9 ± 30.5 mg/dL; P =.69) or subcutaneous insulin (122.0 ± 38.0 mg/dL vs. 127.2 ± 35.5 mg/dL; P =.11) or postoperative surgical complication rates (30-day mortality: 3.5% vs. 1.7%; complications (any): 40% vs. 42%; 30-day re-admissions: 13% vs. 13%; all cardiac complications: 35% vs. 31%; and all infections: 8% vs. 5%). Over an average of 5.1 ± 2.2 years following index surgery, there was higher all-cause mortality among those PS-matched who had experienced hypoglycemia compared to those who had not (log-rank P =.031), primarily due to those (n = 32) experiencing more than one episode of hypoglycemia. Conclusion: Postoperative hypoglycemia did not negatively impact immediate surgical complication rates but was associated with a significant risk of increased postoperative morbidity and long-term all-cause mortality in patients experiencing multiple episodes of hypoglycemia.