['The purpose of this study was to determine if glycemic complexity, along with hypoglycemia and hyperglycemia, was associated with worse outcomes after cardiac surgery.', 'We conducted a retrospective analysis of 970 patients who had insulin infusions designed to keep blood glucose levels between 80 and 110 mg/dL. Glycemic complexity was calculated using jackknifed approximate entropy. Logistic regression was used to adjust for confounders.', 'A total of 495 patients (51%) developed complications, and 32 patients (3.3%) died. Along with older age, comorbidities, and complicated surgeries, any hypoglycemia (glucose<71 mg/dL) and the number of glucose values greater than 140 mg/dL were independent predictors of complications. Increased risk of mortality, after adjusting for other risk factors, was associated with older age, longer perfusion time, receiving intraoperative transfusions, and greater jackknifed approximate entropy of the glucose time series.'] Are hyperglycemia , hypoglycemia , and glycemic complexity associated with worse outcomes after surgery?