Background: Massive transfusion with citrated blood products causes hypocalcemia, which is associated with mortality. Recognition of this problem has led to increased calcium administration; however, the optimal dosing is still unknown.

Study design and methods: This retrospective, single-center study included level 1 trauma patients in 2019 and 2020 who underwent an operation within 12 h of arrival and received a transfusion. Preoperative and intraoperative administrations were totaled to calculate the ratio of administered calcium to the number of blood transfusions for each patient. The citrate content of each blood component was estimated to calculate a second ratio, the ratio of administered calcium to administered citrate. Receiver Operating Characteristic (ROC) curves were performed on both ratios to determine the optimal cutoff values for predicting severe hypocalcemia (ionized calcium <0.9 mmol/L) and hypercalcemia (>1.35 mmol/L) at the end of the intraoperative period.

Results: A total of 506 trauma activations were included, receiving a mean of 17.4 citrated blood products and 16.3 mmol of calcium (equivalent to 2400 mg of calcium chloride). No ratio was statistically significant in differentiating severely hypocalcemic patients from the rest. A calcium to blood ratio of 0.903 mmol of administered calcium per citrated blood product differentiated hypercalcemic patients from the rest.

Discussion: Quantifying received calcium and citrated blood products was insufficient to predict severe hypocalcemia, suggesting other contributions to hypocalcemia. We demonstrated an upper-limit ratio for calcium administration in traumatic hemorrhage; however, further studies are required to determine what calcium dosing regimen results in the best outcomes.