When faced by an external aggression such as shock, sepsis, burns or surgery, the body develops a response, known as stress, comprising hypermetabolism and hypercatabolism related to an alteration in tissue sensitivity to insulin. This alteration seems to be rooted in the transmembrane protein GLUT-4 which takes care of the cell uptake of glucose in skeletal muscle. As a result, there are alterations in the metabolism of carbohydrates, fats and proteins (reduction of immunoglobulins). In the case of surgery, it has been shown that, on the one hand, factors such as rest, pre-operative fasting or the release of inflammatory response factors constrain an even greater alteration in the sensitivity to insulin; and on the other hand that the degree of resistance to insulin depends on the magnitude of the surgery, its duration, bleeding, or on hypothermia and extracorporeal circulation in the case of heart surgery. These metabolic alterations may lead to an increase in the number of infections, mean stay in hospital, and even lead to diabetes mellitus in the long term. Over the last few years, all of this has led several researchers to try to minimize the stress response associated with planned surgery through replacing pre-operative fasting by the administration of carbohydrates, whether or not in association with insulin in perfusion. Beneficial results have been described: control of hyperglycaemia, lower consumption of neoglycogenic amino acids and less alteration of plasma immunity (interleukins, TNF). Future studies will evaluate the influence of these measures on plasma immunity, mean hospital stay and morbidity/mortality.