ATIENTS undergoing major surgery encounter stereotypical alterations in carbohydrate and protein metabolism often referred to as the catabolic response. Characteristic features of impaired carbohydrate homeostasis are increased production of glucose combined with decreased glucose utilization resulting in hyperglycemia. The magnitude of hyperglycemia depends on the severity of surgical tissue trauma. In fasting non-diabetic patients undergoing elective intra-abdominal operations, blood glucose levels increase to 7–10 mmol·L –1 . During cardiac surgery, blood glucose values frequently exceed 15 mmol·L –1 in non-diabetic patients and 20 mmol·L –1 in diabetic subjects. Protein catabolism is characterized by a net loss of body protein. In metabolically healthy patients cumulative nitrogen losses, after elective abdominal operations, range between 40 and 80 g, equivalent to 1.2 to 2.4 kg lean tissue. Postoperative protein loss in patients with type 2 diabetes is 50% greater than in their non-diabetic counterparts. 1 Much of the catabolic profile can be explained by specific neuroendocrine changes, including increased circulating concentrations of cortisol, glucagon, and catecholamines. These hormones exert catabolic effects, either directly or indirectly, by inhibiting insulin secretion and/or counteracting its peripheral action leading to the impairment of tissue insulin sensitivity. The extent of insulin resistance depends on the intensity of trauma, suggesting that insulin resistance is a marker of surgical stress. Clinical significance of the catabolic response to surgery Evidence is mounting that even moderate increases in blood glucose are associated with adverse outcomes. Patients with fasting glucose levels > 7 mmol·L –1 or random blood glucose levels > 11.1 mmol·L –1 on general surgical wards showed an 18-fold increase in in-hospital mortality, a longer length of stay, and a greater risk of infection. 2 In critically ill patients, mortality was directly correlated with increasing glucose levels above 5 mmol·L –1 . 3 In patients undergoing cardiovascular procedures, hyperglycemia was associated with increased mortality and organ dysfunction. 4 Furthermore, detrimental effects of acute hyperglycemia were documented in patients with cerebrovascular disease, myocardial ischemia, and trauma. Erosion of lean tissue protein delays wound healing, compromises immune function, and diminishes muscle strength after surgery. The resulting muscle weakness prolongs mechanical ventilation, inhibits effective coughing, and impedes mobilization. The length of time for return of normal physiologic function after discharge from the hospital is related to the extent of loss of lean body mass during hospitalization. 5