Treatment thresholds for hyperglycemia in critically ill patients with and without diabetes

Excerpt

Hyperglycemia is exceedingly common in critically ill patients. Although there is no accepted definition of acute hyperglycemia in the critical care setting, it is generally considered to be above 180–220 mg/dl (10.0–12.2 mmol/l). In the study by Plummer and colleagues reported in this issue of Intensive Care Medicine only 22.7 % of ICU patients were normoglycemic [1]. Glycemic control and the optimal blood glucose target are a subject of enormous controversy in critically ill patients. Retrospective and cohort studies in both ICU and hospitalized non-ICU patients have demonstrated a strong association between hyperglycemia and poor clinical outcomes [2]. It had therefore been assumed that “strict” glycemic control would improve patient outcomes. In 2001 van den Berghe et al. [3] reported that tight glycemic control (80–110 mg/dl, 4.4–6.1 mmol/l) improved the outcome of critically ill patients in a surgical intensive care unit. Subsequent studies, the most important being the NICE-SUGAR study, demonstrated that intensive glucose control (81–108 mg/dl, 4.5–6.0 mol/l) increased mortality when compared to conventional glucose control (144–180 mg/dl, 8.0–10.0 mmol/l) [4]. We have previously argued that hyperglycemia is a marker of illness severity rather than a cause of poor outcome [5]. Indeed, the degree of hyperglycemia is related to the degree of activation of the stress response. Stress hyperglycemia is regarded as an evolutionary adaptive response which allows the host to survive during periods of severe stress [5]. The neuroendocrine response to stress is characterized by excessive gluconeogenesis, glycogenolysis, and insulin resistance, with increased hepatic output of glucose (gluconeogenesis) being the major cause of stress hyperglycemia. Insects, worms, and all verterbrates including fish develop stress hyperglycemia when exposed to stress [5]. Stress hyperglycemia provides a source of fuel for the immune system and brain at a time of stress. While mild to moderate stress hyperglycemia is protective it is likely that severe stress hyperglycemia may be deleterious. However, the blood glucose threshold above which stress hyperglycemia becomes harmful is unknown. Furthermore, we suggest that both the duration and the degree of hyperglycemia are important in determining whether hyperglycemia is protective or harmful [5]. It seems most unlikely that a few days of hyperglycemia would be harmful; indeed attempts at rapid correction of blood glucose in these patients may be harmful. …