SHM Converge Scientific Abstract ePoster Gallery-Just Add More Water? Challenges With Hypernatremia

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This case describes a 73-year-old woman with diabetes, hypertension, and prior Cushing’s disease who presented with severe weakness, thirst, dizziness, hypovolemia, and hypotension. Although her initial sodium was normal, she required large volumes of IV fluids, vasopressors, and ICU care for persistent hemodynamic instability. Despite aggressive hypotonic IV fluids and drinking about 2 L/day, her sodium remained elevated for two weeks, suggesting impaired free-water regulation rather than simple dehydration.<br /><br />Workup for infection, adrenal insufficiency, and cardiac dysfunction was negative. Serum osmolality was high, while urine studies showed inappropriately variable and not maximally dilute urine. An indirect water deprivation test on hospital day 21 was consistent with partial arginine vasopressin (AVP) deficiency: after desmopressin, her serum sodium normalized and urine osmolality rose appropriately. A later copeptin level was 2.9 pmol/L, supporting AVP deficiency.<br /><br />The likely cause was progression of a known nonfunctional pituitary macroadenoma diagnosed on MRI in 2018. Repeat MRI could not be obtained because of a spinal cord stimulator, but CT of the sella/orbits showed an enlarging left sellar lesion consistent with pituitary macroadenoma.<br /><br />The presentation highlights that partial AVP deficiency can be subtle, sometimes appearing as refractory hypotension, minimal thirst, and failure to correct hypernatremia with increased free-water intake. The case also emphasizes diagnostic pitfalls, especially anchoring bias, overreliance on prior specialist assessments, incomplete outside records, and issues during care transitions.<br /><br />Key teaching points: evaluate hypernatremia systematically, consider partial AVP deficiency in refractory cases, use water deprivation/desmopressin testing when appropriate, and recognize copeptin as a more stable marker than AVP, though overlap can occur in partial deficiency.

Asset Subtitle

Nelly Bellamy

Meta Tag

Author List Christina Kahl, Nelly Bellamy

Category Clinical Vignettes

Concept Hypernatremia

Concept Central Diabetes Insipidus

Concept Diagnostic Evaluation

Concept Arginine Vasopressin Resistance

Concept Water Deprivation Test

Distinguished Non-Finalist

Presenter Organization University of North Carolina at Chapel Hill

Presenting Author Nelly Bellamy

Track Adult

Keywords

partial AVP deficiency

hypernatremia

pituitary macroadenoma

copeptin

desmopressin test

water deprivation test

hypotension

hypovolemia

diabetes insipidus

sellar lesion

Hypernatremia

Central Diabetes Insipidus

Diagnostic Evaluation

Arginine Vasopressin Resistance

Water Deprivation Test