Insulin revisited.

Injury and critical illness are characterised by hyperglycaemia, high free fatty acids and high net protein catabolism, due partly to suppression of insulin secretion in the shock phase and insulin resistance in the flow phase of injury, accompanied by high levels of cytokines and the catabolic hormones cortisol, glucagon and catecholamines. Pre-operative carbohydrate loading reduces post-operative insulin resistance and its consequences. Insulin has been shown to reduce the catabolic response as well as controlling hyperglycaemia. In contrast to its sodium retaining properties in normal, obese and diabetic subjects, insulin-glucose-potassium therapy may induce a sodium diuresis in catabolic patients with salt and water overload and in patients with congestive heart failure in whom haemodynamic improvement has also been observed. Diabetic patients with myocardial infarction and cardiac surgery also benefit from insulin treatment. Recent studies have described positive effects on clinical outcome in critical illness. Whether this is due simply to maintenance of euglycaemia or to the other effects of insulin remains to be determined.