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Background: We sought to review the literature describing the benefits of tight glycemic control in critically ill patients, comparing outcome differences in subgroup populations., Methods: We searched PubMed for relevant literature on the topic of hyperglycemia and its management in the intensive care unit., Results: Overwhelming evidence in both surgical and medical patients conclusively demonstrates that hyperglycemia is a marker of severity of illness and is also an independent determinant of bad outcome, largely from infectious complications. Randomized trial evidence, in conjunction with historically controlled trials, supports the use of intensive insulin therapy and euglycemic control in critically ill patients, with nondiabetics possibly benefiting even more than diabetic patients. Euglycemia is best achieved, and hypoglycemia attenuated, through use of a protocolized approach. Further elaboration as to what threshold range defines euglycemia in patient subpopulations is needed and what pitfalls must be avoided in this practice. Development of continuous blood glucose monitoring has started and will someday be incorporated into routine practice in the same way that continuous electrocardiographic monitoring and pulse oximetry are standards of care in the intensive care unit., Conclusions: Hyperglycemia is a predictor of death and complications in critically ill patients. Early aggregated study results show that control of hyperglycemia improves outcomes. Well-designed studies involving thousands of patients have started to better elucidate the concomitant promoters of hyperglycemia and to better quantify the benefits from tight glycemic control.

Hyperglycemia is frequently seen in acutely ill patients and has historically been viewed as a normal response to stress. Treatment is often not initiated unless blood glucose exceeds 200 to 250 mg/dL. Recent evidence suggests that hyperglycemia is associated with worse outcomes within the population of medical and surgical intensive care units. Hyperglycemia in this population of patients develops from increased gluconeogenesis and insulin resistance. Although the specific mechanisms by which hyperglycemia contributes to poor outcomes are as yet unknown, disruption of normal mitochondrial respiration, direct glucose toxicity, accumulation of asymmetric dimethylarginine, and impairment of immune cell function are among the possibilities implicated. Studies demonstrate that intensive insulin therapy to achieve euglycemia reduces mortality and morbidity in critically ill patients. In addition to recognizing and treating hyperglycemia, it is as important to identify other frequently overlooked factors that contribute to hyperglycemia, such as medications, intravenous fluids, and enteral and parenteral nutrition.