[Eighth Jesús Culebras Lecture. Critical Care, nutrition and hyperglycemia: a close relationship]

Critically ill patients show a metabolic response to injury that affects carbohydrate metabolism, causing hyperglycemia and an increase in glycemic variability that makes the critically ill patient susceptible to infection, resulting in morbidity and mortality increase. Also, severe hypoglycemia was detected as a consequence of intensive insulin treatment that provokes deleterious effects in their clinical evolution, so a correct monitoring of plasma glucose would contribute to reduce morbidity and mortality. In critically ill patients, glucose metabolism is in allostasis stage as a consequence of metabolic stress, producing an increase in peripheral resistance to insulin that causes an imbalance with the pancreatic beta-cell function, increasing insulin secretion to maintain plasma glucose levels within normality ranges. Numerous studies have been published about treatments with insulin and glycemic variability, whereas there are very few about nutrometabolic treatment of hyperglycemia in critically ill patients. Of all of them we can conclude that it is always recommended to keep glucose levels under 180 mg/dl, and when possible, not over 150 mg/dl, establishing a lower range of 110-140 mg/dl. Moreover, tight glycemic control increases the risk of severe hypoglycemia (≤ 40 mg/dl) and its subsequent mortality, so we advise against it. Besides, glycemic variability has been independently associated with an increase of mortality in critically ill patients and, consequently, protocols should aim at avoiding it. Nutritional treatment with diabetes-specific diets not only improves hyperglycemic control and decreases insulin needs, but also decreases glycemic variability and could reduce the incidence of infectious complications. Therefore, they are recommended, at least during the first week of stay. Finally, diabetes seems to modulates the consequences of hyperglycemia in critically ill patients, so diabetic patients could benefit from a higher glycemic target than those without diabetes but with stress hyperglycemia.