Abstract: PUB133
Intractable Hyponatremia, Polydipsia, and the Reset Osmostat: A Case Report
Session Information
Category: Trainee Case Report
- 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Hassan Kamel, Mohamed Taher, Boston Medical Center, Boston, Massachusetts, United States
- Upadhyay, Ashish, Boston Medical Center, Boston, Massachusetts, United States
- Borkan, Steven C., Boston Medical Center, Boston, Massachusetts, United States
Introduction
Water intake in excess of water excretion results in hyponatremia, the most common electrolyte abnormality in clinical practice. Typically, ADH secretion fluctuates to maintain a physiologic serum osmolality, the so called "ADH osmostat". This threshold can be altered by multiple physiologic and pathologic stimuli.
Case Description
A 71-year-old man with severe depression, type II diabetes mellitus and chronic obstructive pulmonary disease presented to the hospital with diffuse weakness, difficulty with focused attention and suicidal ideations. He admitted to drinking more than 15 liters of liquid daily. Home medications included metformin, insulin, lisinopril, amlodipine, metoclopramide, pantoprazole, and trazodone.
Physical exam revealed hypertension and truncal obesity, but was otherwise unremarkable. Laboratory investigation revealed a plasma sodium concentration of 120 mEq/L, blood urea nitrogen of 9 mg/dl, creatinine of 0.82 mg/dL, serum osmolality of 263 mOsm/kg and urine osmolality of 155 mOsm/kg with a urine sodium of 38 mEq/L.
Because of neurological symptoms and worsening hyponatremia, the patient received 3% hypertonic saline infusion. Serum sodium was noted to fluctuate during periods of unsupervised access to fluid, hypertonic saline infusion and fluid restriction. Urine osmolality was also noted to flucutate, dropping appropriately with worsening hyponatremia and rising with fluid restriction, hypertonic saline and resultant rise in serum sodium. The rise in urine osmolality occured without normalization of serum sodium.
Discussion
In this report, we present a case of symptomatic hyponatremia associated with polydipsia in an elderly patient with psychiatric comorbidities and chronic hyponatremia. We describe the accompanying laboratory findings that support the diagnosis of reset osmostat. We postulate that chronc hyponatremia secondary to polydipsia related to psychiatric illness could have reset this patient's osmostat and discuss potential therapeutic strategies.