Glucose control and clinical outcomes in surgical patients: A narrative review

Perioperative hyperglycemia occurs in up to 40% of noncardiac and 80% of cardiac surgery patients, frequently independent of a diabetes diagnosis; it is driven by the neuroendocrine stress response, inflammatory cytokine release, and postoperative insulin resistance. Elevated glucose promotes protein glycosylation, which impairs wound healing and immune function, and it has been consistently associated with surgical site infection, anastomotic leak, prolonged length of stay, and increased mortality across surgical subspecialties. This narrative review examines biochemical aspects of glycogen metabolism and stress-induced insulin resistance, synthesizes evidence linking hemoglobin A1c (HbA1c) thresholds to surgical outcomes, and summarizes contemporary guidelines from the American Diabetes Association, Endocrine Society, European Society of Cardiology, Society of Critical Care Medicine, and Surviving Sepsis Campaign. Current consensus favors moderate, protocolized glucose targets (generally 100-180 mg/dL) while avoiding iatrogenic hypoglycemia. Preoperative optimization toward an HbA1c near 7%, judicious carbohydrate loading, and avoidance of glycemic extremes offer meaningful, modifiable strategies to improve outcomes in surgical and critically ill surgical patients.