A 35-year-old man receives a massive transfusion of 15 units of packed red cells, 12 units of FFP, and 2 units of platelets for a Grade V liver laceration. During surgery, the cardiac monitor shows widened QRS complexes and prolonged QT interval. Serum ionized calcium is measured at 0.72 mmol/L (normal 1.15-1.33). What is the mechanism of this complication?

• A Hypothermia from cold blood products suppresses parathyroid hormone
• B Massive transfusion causes renal calcium wasting
• C FFP contains EDTA that binds serum calcium irreversibly
• D Citrate in stored blood products chelates ionized calcium ✓

Explanation

Citrate is the anticoagulant in stored blood products and is normally metabolized by the liver. During massive transfusion, citrate load overwhelms hepatic metabolism, causing ionized hypocalcemia by chelation. This manifests as prolonged QT, hypotension, and decreased myocardial contractility. Ionized calcium should be monitored and replaced during massive transfusion. Hypothermia coexists but does not cause hypocalcemia directly.

Reference: Bailey and Love's Short Practice of Surgery, 28th ed.

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Written and medically reviewed by the StethoPrep medical team.