Abstract
We report two cases of post-surgical mineralocorticoid-responsive hyponatremia of the elderly (MRHE). First, a seventy five-year-old man underwent right hemi-lobectomy for hepatocellular carcinoma. Although his plasma sodium level was 134 mEq/L on postoperative day (POD) 1, he had hyponatremia (Na : 111 mEq/L) accompanied by impaired consciousness on POD3. The second case is of a seventy two-year-old woman who underwent laparoscopic ileocecal resection. She also had hyponatremia (Na : 113 mEq/L) accompanied by impaired consciousness on POD2 despite a normal level of sodium on POD1. Both patients had low serum osmotic pressure, high urine osmotic pressure, and normal adrenal function. Although the two patients almost fulfilled the criteria for the syndrome of inappropriate antidiuretic hormone secretion, we diagnosed them with MRHE because of the presence of mild dehydration. They recovered with fluid replacement and fludrocortisone acetate. MRHE is considered mildly hypovolemic hyponatremia caused by renal sodium loss. Decreased sodium retention leads to volume depletion. Plasma anti-diuretic hormone levels are elevated because of such hypovolemia. The possibility of MRHE should be considered in the perioperative course of elderly patients.
