RF25 | PMON113 Subarachnoid Hemorrhage Complicated by Nephrogenic and Central Diabetes Insipidus
Authors: Arora Ipsa , Lechan Ronald , Kung Jacqueline , McCallum Wendy 
Published: November 2022

Abstract

Introduction
Diabetes insipidus (DI) is a rare complication of subarachnoid hemorrhage (SAH) and associated with worse prognosis and increased mortality. We present a case of combined nephrogenic and central DI together with osmotic diuresis as a result of SAH and discuss the pathophysiology.

Case
A 63-year-old female without significant past medical history was found unresponsive. CT head followed by angiography confirmed extensive SAH arising from a saccular anterior communicating artery (Acoma) aneurysm. She underwent emergent coil embolization and right frontal external ventriculostomy drain placement. Postoperatively, she developed polyuria (300-400 mL/hour) and hypernatremia (156 mEq/L) concerning for the development of DI. Serum osmolality was elevated at 316 mOsm/kg, urine osmolality inappropriately low relative to serum osmolality at 289 mOsm/kg but also unexpectedly high for complete DI, serum potassium 2.9 mEq/L and urine potassium elevated urine at 9 mEq/L. Serum copeptin was 6 pmol/L and inappropriately low for nephrogenic DI, suggesting a mixed central and peripheral process as well as contribution from osmotic diuresis. Intravenous (IV) desmopressin (DDAVP) only slightly reduced the polyuria. Management was complicated by adypsia and persistent hypokalemia requiring ongoing replacement. IV fluid, which had initially consisted of high-osmolality Plasma-Lyte (294 mOsm/L), matched to urine output, was switched to D5W, leading to a significant decrease in polyuria. On post-operative day 17, DDAVP was discontinued with normalization of sodium (137 mEq/L), potassium (3.8 mEq/L) and urine output. Three months post-operatively, she was asymptomatic with intact pituitary function and no hypokalemia.

Discussion
Hypokalemia in patients with SAH is thought due to acute intracellular shift of potassium caused by excessive β2-adrenergic activity generated endogenously by the sympathetic nervous system. In our patient, there was also likely contribution from distal tubular delivery of sodium from osmotic diuresis, leading to increased urinary potassium losses and hypokalemia-induced partial nephrogenic DI which was further complicated by partial central DI as suggested by the inappropriately low copeptin level for nephrogenic DI in face of a high serum osmolality and inappropriately low urine osmolality. As the vascular supply to anterior hypothalamus is derived from the Acoma, rupture may compromise perfusion affecting neuronal populations in the lamina terminalis that regulate thirst and AVP secretion in response to hyperosmolarity. Early detection of DI is critical because hypovolemia can predispose to cerebral vasospasm and worsen outcomes. This case also depicts the importance of careful consideration of sources of osmolar loads such as the composition of administered IV fluids, and aggressive potassium replacement to maintain DDAVP sensitivity.

Conclusion
DI should be considered in polyuria syndrome with hypernatremia after a neurosurgical event. Nephrogenic and central DI and adypsia can manifest following SAH, with sources of iatrogenic osmolar load further complicating the clinical picture. Early recognition and treatment may reduce morbidity and mortality.
Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m., Monday, June 13, 2022 1:12 p.m. - 1:17 p.m.