Blood glucose management during critical illness.

Abstract

The term “stress hyperglycemia” is used to describe an altered metabolic state induced by acute illness characterized by transient elevations in blood glucose in individuals who lack a previous history of diabetes [1]. Many patients regain normal glycemic status once the acute illness resolves; however, stress hyperglycemia may also be a harbinger of subsequent diabetes. Husband et al. studied patients not known to have diabetes who were hyperglycemic following admission for suspected acute myocardial infarction; 63% had glucose tolerance tests consistent with diabetes two months later [2]. The reported incidence of stress hyperglycemia in hospitalized patients varies due to inconsistencies in criteria used to define the condition; blood glucose concentrations ranging from 6.7 to 11.2 mmol/L have been proposed by various authors [1]. Determination of the true incidence of stress hyperglycemia is further obscured by the fact that some studies included patients with preexisting diabetes mellitus. The reported prevalence of stress hyperglycemia also varies based on the severity of illness in the patient population surveyed; one study of critically-ill patients with sepsis or severe trauma reported an incidence of stress hyperglycemia of approximately 50% [3]. The presence of a hyperglycemic milieu during critical illness is associated with a number of adverse consequences such as: increased incidence of wound infections post-operatively, and worsened outcome in head injury, stroke, and myocardial infarction [4–6]. A recent study examined the hospital records of approximately 2000 adult patients; hyperglycemia was present in 38% of patients admitted to the hospital; of these, 1/3 had no previous history of diabetes. Patients with newly discovered hyperglycemia were found to have a higher in-hospital mortality (16%) when compared to those patients who were known to be diabetic (3%), or to those who were normoglycemic (1.7%). The group with newly discovered hyperglycemia also had an increased duration of hospitalization, were more likely to be admitted to the ICU, and had a greater probability of requiring nursing home care at discharge [7]. Aggressive treatment of hyperglycemia in diabetics who are postoperative or who are critically ill has been shown to be beneficial by reducing infectious risk. In contrast, there is a paucity of data supporting tight control in patients with stress hyperglycemia, and many clinicians ignore modest elevations in blood glucose in this population. This article will review the pathophysiology of hyperglycemia during acute illness, examine data that demonstrate benefits of tight glycemic control, and describe an approach to management of this condition.