Hemoglobin A1c and Permissive Hyperglycemia in Patients in the Intensive Care Unit with Diabetes.

Glycated hemoglobin A1c can be used to assess intensive care unit patients' level of chronic glycemic control. Compared with patients with normal glycated hemoglobin A1c, patients with elevated glycated hemoglobin A1c seem to better tolerate hyperglycemia and large glucose fluctuations during critical illness. The risks associated with hypoglycemia are markedly greater among patients with elevated glycated hemoglobin A1c. Observational studies suggest that more liberal targets further decrease the occurrence of hypoglycemia in patients with diabetes with elevated glycated hemoglobin A1c. Whether glycated hemoglobin A1c should be used to individualize glucose control during critical illness should be assessed in randomized trials.