Robert M. Centor, MD


November 27, 2006

This series of cases offers an opportunity for you to work through the diagnostic process, determining what tests to order and which questions to ask. A discussion link is provided below to facilitate that process.

Case Presentation

A 42-year-old man with known HIV infection is admitted with headache and a fever. The physicians diagnose cryptococcal meningitis and start amphotericin B and 5-fluorocytosine (5-FC). One week later, on rounds, the patient is found to be confused.

Laboratory Analyses

Electrolyte panel: Sodium 152 mEq/L; potassium 3.4 152 mEq/L; chloride 120 152 mEq/L; bicarbonate 20 152 mEq/L; blood urea nitrogen (BUN) 32; creatinine 1.4 mg/dL; glucose 112 mg/dL

Arterial blood gas: pH 7.30; pCO2 36; pO2 85

Plasma osmolality 315 mOsm/kg; urine osmolality 150 mOsm/kg; urine Na+ 25 mEq/L; urine K+ 45mEq/L; urine Cl- 38mEq/L; urine pH 6.2

The Problem

What is the likely cause of his hypernatremia?

What is the acid-base disorder and what caused it?


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