A 70-year-old male with chronic renal failure on hemodialysis presents to the triage desk with severe generalized weakness and peaked T waves on 12-lead ECG. Point-of-care serum potassium is 7.2 mmol/L. What is the immediate first-line intravenous medication administered to stabilize the cardiac myocyte membrane against fatal ventricular fibrillation?

Answer and explanation

Correct answer: A. Intravenous Calcium Gluconate

  1. Step 1: Severe hyperkalemia (> 6.5 mmol/L) with ECG changes (peaked T waves, widened QRS, PR prolongation) is a lethal cardiac emergency.
  2. Step 2: Intravenous Calcium Gluconate (10 mL of 10% solution over 2-3 minutes) antagonizes the membrane actions of hyperkalemia by restoring normal resting membrane potential thresholds, stabilizing the myocardium within 1 to 3 minutes.
Answer
Intravenous Calcium Gluconate.
Why not the others: 'Insulin and Dextrose' shifts potassium intracellularly, but takes 15 to 30 minutes to act and does not provide immediate membrane stabilization; 'Sodium Polystyrene Sulfonate' removes potassium via the bowel over hours to days; 'Furosemide' promotes renal potassium excretion but has zero effect in anuric hemodialysis patients.

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