Hypocalcemia is the Most Likely Complication
In a patient with hypovolemic shock from a road traffic accident receiving 4 liters of blood transfusion, hypocalcemia (Option A) is the most likely complication due to citrate-mediated calcium chelation from blood products.
Mechanism of Transfusion-Associated Hypocalcemia
- Each unit of packed red blood cells or fresh frozen plasma contains approximately 3 grams of citrate, which binds ionized calcium and removes it from circulation 1, 2.
- During massive transfusion (typically defined as ≥4 units in 1 hour or ≥10 units in 24 hours), citrate accumulation causes progressive hypocalcemia 3.
- The citrate-calcium binding occurs immediately upon transfusion, making hypocalcemia an early and predictable complication 1, 4.
Clinical Significance in Trauma
- Hypocalcemia within the first 24 hours of critical bleeding predicts mortality with greater accuracy than fibrinogen, acidosis, or platelet count 1.
- Low ionized calcium at admission is associated with platelet dysfunction, decreased clot strength, increased blood transfusion requirements, and higher mortality 4, 2.
- Trauma patients commonly have impaired citrate metabolism due to hypoperfusion, hypothermia, and hepatic insufficiency, which exacerbates hypocalcemia 1, 2.
Why Not the Other Options
Hypokalemia (Option B) is less likely in the acute trauma setting:
- Hyperkalemia is actually more common initially in massive transfusion due to potassium release from stored blood products 5.
- Hypokalemia typically develops later during prolonged intensive care or dialysis, not acutely with 4L transfusion 5.
Hyperalbuminemia (Option C) does not occur with blood transfusion:
- Blood products do not contain sufficient albumin to cause hyperalbuminemia 3.
- Trauma and shock typically cause hypoalbuminemia due to capillary leak and dilution, not hyperalbuminemia 6, 7.
Monitoring and Treatment Recommendations
- Ionized calcium should be monitored at baseline and every 4-6 hours during intermittent transfusions, or every 1-4 hours during continuous massive transfusion 2.
- Calcium chloride is the preferred agent for correction, administered at 1 gram per liter of citrated blood products transfused to maintain ionized calcium >0.9 mmol/L 2.
- Calcium chloride 10% solution (10 mL contains 270 mg elemental calcium) is superior to calcium gluconate (10 mL contains only 90 mg elemental calcium) for rapid correction 1, 4, 2.
Critical Pitfalls to Avoid
- Do not wait for symptoms to develop before treating hypocalcemia in massive transfusion—prophylactic calcium administration is recommended 4, 2.
- Cardiac dysrhythmias become particularly concerning when ionized calcium falls below 0.8 mmol/L 4, 2.
- Do not administer calcium through the same IV line as sodium bicarbonate due to precipitation risk 1, 4.
- Maintain normothermia and pH above 7.2, as acidosis and hypothermia impair citrate metabolism and worsen hypocalcemia 8.