Critical Care Medicine-Renal, Electrolyte and Acid Base Disorders>>>>>Sodium
Question 9#

A 19-year-old woman with past medical history of type I diabetes mellitus and seizures on oxcarbazepine is admitted for fever, chills, and myalgia. She works as a nurse assistant in the local skilled nursing facility where a few patients recently have been diagnosed with the flu. Her appetite has been poor since her symptoms started, and she also reports bouts of diarrhea. On physical examination, she is febrile with a temperature of 38.7°C, blood pressure is 102/76 mm Hg, pulse rate is 120 beats/min, and respiratory rate is 12 breaths/min. Laboratory values show the following:

• Sodium 130 mEq/L (mmol/L)
• Potassium 4.1 mEq/L (mmol/L)
• Chloride 95 (mmol/L)
• Bicarbonate 9 (mmol/L)
• BUN 9 mg/dL
• Creatinine 0.7 mg/dL
• Glucose 623 mg/dL 

What is the MOST likely underlying cause for her hyponatremia?

A. Poor solute intake
B. SIADH
C. Medication related
D. Hyperglycemia
E. Diarrhea

Correct Answer is D

Comment:

Correct Answer: D

Glucose is an osmotically active solute. In the presence of hyperglycemia, the serum osmolality increases which leads to water movement out of the cells. This leads to a dilutional hyponatremia. Generally, for any glucose level greater that 100 mg/dL, an additional 1.6 mEq/L should be added to the measured serum sodium level. In this case, the patient’s corrected sodium level is approximately 138 mEq/L.

Reference:

1. Liamis G, Liberopoulos E, Barkas F, Elisaf M. Diabetes mellitus and electrolyte disorders. World J Clin Cases. 2014;2(10):488-496.