Abstract: FR-PO0887
Shifting Set Points: Reset Osmostat in a Dynamic Hypernatremic State
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 1
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Santos, James Urbano, Stony Brook University Hospital, Stony Brook, New York, United States
- Daccueil, Farah, Stony Brook University Hospital, Stony Brook, New York, United States
- Hassan Kamel, Mohamed Taher, Stony Brook University Hospital, Stony Brook, New York, United States
Introduction
Hypernatremia is the pathophysiologic result of total body water defict. Here we report a case of acute on chronic severe hypernatremia refractory to correction with associated relative polyuria and fluctuating urine osmolarity. This pattern was consistent with a hypernatremia reset osmostat.
Case Description
A 22-year-old non-verbal female with Seckel syndrome, Dandy-Walker syndrome (ht 104 cm, wt 17.7 kg) presented with increased work of breathing after a suspected aspiration on a recently changed high-calorie diet. Her previous labs within the last year had noted a serum sodium above lab assay. In ED, she was febrile (38.1°C), tachycardic (150 bpm), tachypneic (25 cpm), hypotensive, and hypoxemic (SpO2 88%). Serum sodium was 192 mEq/L and serum glucose 511 mg/dL. Head CT showed corpus callosum agenesis, associated with Seckel syndrome. Piperacillin/tazobactam was started for aspiration pneumonia and hypernatremia was managed with normal saline, then transitioned to D5W. Initially hypernatremia was attributed to insensible losses, inadequate free water intake, and osmotic diuresis. Despite persistent hypernatremia, the patient was noted to be polyuric with urine that was more dilute than her serum osmolarity. By day 7, serum sodium was 147 mEq/L, urine osmolality 161 mOsm/kg raising concern for a reset osmostat. Indirect water deprivation test was performed; urine osmolality rose to 444 mOsm/kg before discontinuation at the family's request, suggesting intact ADH axis; favoring a reset osmostat.
Discussion
This case highlights multiple hypernatremia etiologies within one hospital stay, including free-water deficit, insensible losses, osmotic diuresis. More importantly, this case unmasked a reset osmostat where there was preservation of both concentration and dilution at a serum sodium 152mEq/L.This highlights the importance of always re-assessing the presenting data while managing allowing room for shift in management for a great clinical outcome.