What electrolyte abnormality is a patient at greatest risk of due to massive transfusion protocol (Massive Transfusion Protocol) after a traumatic injury?

From the Guidelines

Hypocalcemia is the electrolyte abnormality that patients are at greatest risk of during massive transfusion protocol (MTP) after traumatic injury. This occurs because blood products used in MTP, particularly packed red blood cells and fresh frozen plasma, contain citrate as an anticoagulant. When large volumes are transfused rapidly, citrate binds to calcium in the patient's bloodstream, reducing the levels of ionized calcium available for vital physiological functions. Calcium is essential for normal cardiac contractility, coagulation, and neuromuscular function. Clinically significant hypocalcemia can manifest as cardiac arrhythmias, hypotension, prolonged QT interval, tetany, and worsening of coagulopathy. To prevent these complications, calcium supplementation (typically as calcium chloride) should be administered prophylactically during MTP, with additional doses guided by ionized calcium measurements, as recommended by the European guideline on management of major bleeding and coagulopathy following trauma: sixth edition 1.

Key Points

• Hypocalcemia is a significant concern during MTP due to the citrate-mediated chelation of serum calcium in blood products.
• Ionized calcium levels should be monitored and maintained within the normal range (1.1-1.3 mmol/L) during MTP, with calcium chloride administration to correct hypocalcemia 1.
• The normal range of ionized calcium is pH-dependent, and a 0.1 unit increase in pH decreases ionized calcium concentration by approximately 0.05 mmol/L 1.
• Calcium is essential for the formation and stabilization of fibrin polymerization sites, platelet-related functions, cardiac contractility, and systemic vascular resistance.
• Clinically significant hypocalcemia can manifest as cardiac arrhythmias, hypotension, prolonged QT interval, tetany, and worsening of coagulopathy.

Management

• Calcium supplementation should be administered prophylactically during MTP, with additional doses guided by ionized calcium measurements.
• Calcium chloride is the preferred agent to correct hypocalcemia, as it contains more elemental calcium than calcium gluconate and may be preferable in the setting of abnormal liver function 1.

From the Research

Electrolyte Abnormality Risk in Massive Transfusion Protocol

The patient in question, a 22-year-old man presenting with a gunshot wound to his abdomen and undergoing massive transfusion protocol, is at greatest risk of developing hypocalcemia due to the transfusion.

• Hypocalcemia is a common complication in patients receiving massive transfusions, with studies indicating that 97% of patients may experience hypocalcemia during the first six hours of resuscitation 2.
• The condition is associated with increased mortality in trauma patients with hemorrhagic shock who require massive transfusion protocols (MTPs) 3.
• Severe hypocalcemia is correlated with the number of packed red blood cells transfused, with patients receiving 13 or more units of PRBCs having a greater prevalence of hypocalcemia 4.
• The incidence of hypocalcemia in MTP has been reported to be as high as 85-97%, with calcium supplementation not being standardized in MTP, potentially leading to underutilization during massive transfusion and resulting hypocalcemia 2.

Key Findings

• A retrospective study found that the incidence of hypocalcemia within 24 hours was significantly lower in patients who received a calcium replacement protocol during MTP 3.
• Another study reported that patients with severe hypocalcemia had higher baseline activated partial thromboplastin time, higher lactic acid, lower platelets, and lower pH, with mortality being higher in the severe hypocalcemia group 5.
• Research suggests that standardized protocols for recognition and management of severe hypocalcemia during massive transfusions may improve outcomes 4.

Calcium Replacement

• The optimal ratio of grams of citrate to calcium milliequivalents (mEq) for reducing 30-day mortality in patients receiving MTP is still being studied, with one study suggesting a Citrate:Ca ratio between 2 and 3 may be sufficient to obtain a normalized ionized calcium level within 24 hours of MTP activation 6.