A 68-year-old male with end-stage renal disease misses two consecutive hemodialysis sessions. He presents with severe generalized muscle weakness. ECG demonstrates tall peaked T-waves, PR interval prolongation, and widening of the QRS complex. Serum potassium is 7.4 mEq/L. What is the immediate first-line medication to prevent fatal cardiac arrhythmias?

Answer and explanation

Correct answer: C. Intravenous Calcium Gluconate (10%)

  1. Step 1: Severe hyperkalemia with ECG changes (peaked T waves, QRS widening) is a lethal medical emergency requiring immediate cardiac membrane stabilization.
  2. Step 2: Intravenous Calcium Gluconate (10 mL of 10% solution over 2-3 minutes) antagonizes the membrane excitability effects of hyperkalemia within 1 to 3 minutes, restoring the normal threshold potential without altering serum potassium concentration.
  3. Step 3: Once the myocardium is stabilized, intracellular shifting agents (insulin + dextrose, albuterol) and elimination therapies (hemodialysis) are administered.
Answer
Intravenous Calcium Gluconate (10%).
Why not the others: 'Insulin with Dextrose' shifts potassium intracellularly within 15-30 minutes but does not immediately stabilize the myocardial membrane; 'Nebulized Albuterol' takes 20-30 minutes; 'Sodium Polystyrene Sulfonate' is a slow-acting gastrointestinal resin taking hours to days.

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