A patient is receiving an intravenous infusion of regular insulin for diabetic ketoacidosis. The nurse knows that as blood glucose decreases, insulin shifts potassium into cells. At what serum potassium threshold should insulin infusion be temporarily withheld and potassium replacement initiated to prevent fatal cardiac arrhythmias?

Answer and explanation

Correct answer: A. < 3.3 mmol/L

  1. Step 1: Insulin stimulates the Na+/K+-ATPase pump, driving potassium into skeletal muscle and hepatic cells.
  2. Step 2: International DKA protocols mandate that if baseline serum potassium is below 3.3 mmol/L, insulin must be withheld and potassium repleted (20-30 mEq/hr) until potassium exceeds 3.3 mmol/L to prevent fatal ventricular arrhythmias and respiratory arrest.
Answer
< 3.3 mmol/L.
Why not the others: '< 5.0 mmol/L' is normal physiological potassium; '< 4.0 mmol/L' is within the safe range to continue insulin with concurrent maintenance potassium supplementation; '< 2.5 mmol/L' represents severe, life-threatening hypokalemia that should never be permitted to develop.

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