A 32-year-old trauma patient receives 12 units of packed red blood cells, 10 units of fresh frozen plasma, and 10 units of platelets over 4 hours (massive transfusion). Which metabolic complication is MOST likely to occur specifically from the stored blood itself?
- A Hypercalcaemia
- B Metabolic alkalosis and hypernatraemia
- C Hyperkalaemia, hypocalcaemia and hypothermia ✓
- D Hypermagnesaemia and respiratory alkalosis
Explanation
Stored packed red blood cells undergo progressive changes: potassium leaks from RBCs raising K+ concentration (causing hyperkalaemia), citrate preservative chelates ionised calcium (causing hypocalcaemia, reducing myocardial contractility), and blood stored at 4°C causes hypothermia when transfused rapidly. Additionally, citrate metabolism is impaired in hypothermia and liver disease, worsening hypocalcaemia. These three — hyperkalaemia, hypocalcaemia, and hypothermia — constitute the 'lethal triad' and directly impair coagulation (alongside acidosis), creating the haemorrhagic shock death spiral.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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