Question of the Week

For July 8, 2014

An 82-year-old man with type 2 diabetes is brought to the emergency department for mental status changes and diarrhea. For the past 5 days, he has had watery diarrhea with six to eight bowel movements per day. He resides in an assisted living facility and was initially determined to be alert and oriented. Recently, however, the staff at the facility noticed that he was confused. On review of his medications, it was discovered that he had not taken his insulin for the past 2 to 3 days.

On examination, he is afebrile and has a blood pressure of 96/70 mm Hg and a heart rate of 94 beats per minute.

Laboratory testing yields the following results:

Patient value

Reference range

Sodium (mEq/liter)

150

136–145

Potassium (mEq/liter)

5.1

3.5–5.0

Random glucose (mg/dL)

1100

<140

Creatinine (mg/dL)

2.8

0.8–1.3

Blood urea nitrogen (mg/dL)

42

10–20

Plasma osmolality (mOsm/kg serum water)

375

285–295

Which one of the following sets of electrolyte changes would be expected to occur if only intravenous insulin is administered?

A decrease in the serum sodium level and an increase in the serum potassium level
An increase in the serum sodium and potassium levels
An increase in the serum sodium level and a decrease in the serum potassium level
No change in the serum sodium level and an increase in the serum potassium level
A decrease in the serum sodium and potassium levels

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