Hyperosmolar Hyperglycemic State

Hyperosmolar hyperglycemic state, formerly hyperosmolar non-ketotic coma, is a metabolic emergency typically affecting older patients with type 2 diabetes. Diagnostic criteria are plasma glucose >600 mg/dL, effective serum osmolality >320 mOsm/kg, mild metabolic acidosis (pH >7.30), bicarbonate >18 mEq/L, and absent to minimal ketonemia.

The pathophysiology involves residual insulin secretion that prevents lipolysis and ketogenesis but is insufficient to control hyperglycemia, producing massive osmotic diuresis, profound dehydration (8-12 liters total water deficit), and altered mental status correlating with osmolality. Mortality reaches 5-20%, much higher than DKA.

Common precipitants are infection (40-60%, especially pneumonia and UTI), MI, stroke, medication non-adherence, glucocorticoids, atypical antipsychotics, and decompensated heart failure. Management priorities are aggressive isotonic fluid resuscitation (1-1.5 L NS in first hour, then 250-500 mL/h with switch to half-normal saline based on corrected sodium), low-dose insulin infusion (0.05-0.1 U/kg/h after volume restoration), potassium replacement, identification of precipitant, and DVT prophylaxis. Slower correction of glucose (50-75 mg/dL/h) is critical to avoid cerebral edema. Discharge with diabetes education and adjusted regimen.