Surgery>>>>>Fluid and Electrolyte Management of the Surgical Patient
Question 27#

An elderly diabetic patient who has acute cholecystitis is found to have a serum sodium level of 122 mEq/L and a blood glucose of 600 mg/dL. After correcting the glucose concentration to 100 mg/dL with insulin, the serum sodium concentration would:

A. Decrease significantly unless the patient also received 3% saline
B. Decrease transiently but return to approximately 122 mEq/L without specific therapy
C. Remain essentially unchanged
D. Increase to the normal range without specific therapy

Correct Answer is D

Comment:

A rise in the extracellular fluid concentration of a substance that does not diffuse passively across cell membranes ( eg, glucose or urea) causes an increase in effective osmotic pressure, a transfer of water from cells, and dilutional hyponatremia. For each 100 mg/dL rise in blood glucose above normal, the serum sodium level falls approximately to 3 mEq/L. Alternatively, the serum sodium level would increase by about 15 mEq/L if the blood glucose level fell from 600 to 100 mg/dL.