(1508) A Rare Case of Polyuria Secondary to Vasopressin Withdrawal in a Critically Ill Patient

Introduction: Vasopressin (VP) or antidiuretic hormone is released in response to hypovolemia or plasma hyperosmolarity. It stimulates V1 receptors on vascular smooth muscle cells causing vasoconstriction. It also stimulates V2 receptors on renal distal convoluted tubules and collecting ducts to enhance water reabsorption. These mechanisms make VP an important vasopressor to treat critically ill patients in shock. This is a rare case of vasopressin withdrawal induced polyuria.

Description: A 67-year-old male with history of hypothyroidism and deep vein thrombosis on warfarin, presented with nausea and coffee-ground emesis for 3 days. On presentation, vitals and physical examination were within normal limits. Labs showed leukocytosis and elevated lactic acid. CT abdomen with contrast revealed a large hiatal hernia with gastric obstruction. He was managed with bowel rest and nasogastric tube insertion for gastric decompression. An esophagogastroduodenoscopy revealed gastric body ischemia with ulceration and eschar extending into the hiatal hernia. Post procedure, he developed respiratory failure requiring mechanical ventilation and shock requiring vasopressor support with norepinephrine and VP. Over the next 24 hours, an attempt to discontinue VP resulted in an increased urine output to 1 L/h within 3 hours. Serum sodium increased from 132 to 141 mmol/L, serum osmolality was 295 mOsm/kg and urine osmolality was 76 mOsm/kg. VP was restarted at 2.4 U/h with improvement in urine output. Subsequent attempts to wean off VP also resulted in polyuria requiring reinitiation of VP with consequent improvement in urine output. The patient underwent surgical repair of the hiatal hernia. Post procedure, vasopressin was decreased by 0.8U/h and gradually weaned off. Over the next 24 hours, sedation was weaned off, the patient was extubated and downgraded to the medical floors.

Discussion: VP is valued for its beneficial hemodynamic effects and is a commonly used vasopressor in the ICU. However, abrupt discontinuation of VP can trigger a transient state of diabetes insipidus, leading to polyuria, volume depletion, hemodynamic instability, and electrolyte imbalance. Although this condition is usually transient, severe cases can be managed with desmopressin.