A trauma patient receives 15 units of packed red blood cells over 2 hours for ongoing hemorrhage. He develops perioral tingling, carpopedal spasm, and a prolonged QT interval on the monitor. Serum calcium is 6.8 mg/dL. What is the most likely cause of this complication?

• A Hyperkalemia from stored blood
• B Citrate toxicity causing hypocalcemia ✓
• C Hypomagnesemia from massive transfusion
• D Hypothermia from rapid transfusion

Explanation

Citrate in stored blood binds ionized calcium, leading to acute hypocalcemia. This manifests as neuromuscular irritability, tetany, prolonged QT, and hemodynamic instability. Hyperkalemia causes peaked T waves and widened QRS. Hypomagnesemia can also cause tetany but is less common. Hypothermia causes coagulopathy and arrhythmias but not this specific ionized calcium picture. Prophylactic calcium supplementation is recommended during massive transfusion.

Reference: Sabiston Textbook of Surgery, 21st ed.

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