How to Evaluate and Treat Acute Onset Hypernatremia

In Episode 43 of Med School Question of the Week for USMLE, Faustine Ramirez, MedSchoolCoach expert tutor, answers this medical school question: A 65-year-old man is admitted to the hospital with two days of fever, productive cough, and poor oral intake. His past medical history includes coronary artery disease, hypertension, congestive heart failure, and type 2 diabetes. His medications include aspirin, atorvastatin, lisinopril, metoprolol, and metformin. He has a 40 pack-year smoking history and drinks alcohol occasionally. Prior to the admission he was feeling well and reports adherence to his medications. Temperature is 38.5 C, heart rate is 105/min, respiratory rate is 22/min, and oxygen saturation is 92%. Physical examination reveals a thin, tired appearing man. Mucous membranes are slightly dry. Capillary refill time is 2-3 seconds. Pulmonary examination demonstrates increased tactile fremitus, dullness to percussion, and crackles over the right lower lung. Neck veins are not distended. There is no peripheral edema. The rest of the examination is unremarkable. Upon admission, laboratory results demonstrate: Sodium 132 / Potassium 4.2 / Chloride 103 / Bicarbonate 26 A chest XR shows a lobar consolidation in the right lower lobe. He is diagnosed with pneumonia, and antibiotics and maintenance IVF with 0.9% normal saline are initiated. The next morning, laboratory studies are repeated: Sodium 128 / Potassium 4.3 / Chloride 101 / Bicarbonate 25 Additional urine and serum studies are obtained and reveal: Urine Na 54 / Urine osmolality 162 / Serum osmolality 268

• What is the most appropriate next step?
• Hypertonic saline
• Desmopressin
• Water restriction
• Dialysis
• Tolvaptan
• Switch to a different class of antibiotics
• High sodium diet