An Analysis of the Incidence of Hypocalcemia in Wartime Trauma Casualties.

OBJECTIVE

Background: Massive transfusion protocols implement the use of blood products to restore homeostasis. Citrated blood products are required for massive transfusions and can induce hypocalcemia, resulting in decreased cardiac contractility. Recent data suggests that major trauma alone is associated with hypocalcemia. This phenomenon remains poorly described. We seek to characterize the incidence and risk factors for early hypocalcemia in the setting of combat trauma.

MATERIALS AND METHODS

This is a secondary analysis of previously described data from the Department of Defense Trauma Registry from January 2007 to March 2020. In this sub-analysis, we selected only casualties that had at least one ionized calcium measurement. We defined hypocalcemia as an ionized calcium level of less than 1.2mmol/L.

RESULTS

Within our study database, there were 142 adult casualties that met inclusion with at least one calcium value documented. We found 72 (51%) experienced at least one episode of hypocalcemia. Median composite injury severity score (ISS) was significantly lower in the control cohort compared to those with hypocalcemia (9 versus 15, p=0.010). Survival was similar between the two groups (97% versus 90%, p=0.166). On multivariable analysis when evaluating serious injuries by body region, only serious injuries to the extremities were significantly associated with developing hypocalcemia (odds ratio [OR] 1.48, 95% confidence interval [CI] 1.00-2.21). When comparing prehospital interventions, only intravenous (IV) fluid administration was associated with high proportions experiencing hypocalcemia (25% versus 43%, p=0.029). In the multivariable model adjusted for ISS, mechanism of injury, and patient category, IV fluids were associated with the development of hypocalcemia (OR 2.48, 95% CI 1.03-5.94). When comparing vital signs, only respiratory rates were noted to be higher in the hypocalcemia cohort (18.6 versus 20.4, p=0.048).

CONCLUSIONS

Approximately half of combat casualties with available ionized calcium (iCa) level were hypocalcemic. Prehospital IV fluid use was associated with the development of hypocalcemia. Our study has implications for forward-staged medical teams with limited laboratory analysis capabilities. Additional research is needed to determine whether calcium replacement improves survival from traumatic injury and to identify the specific indications and timing for calcium replacement. This study will help inform a clinical study intended to aid in the development of clinical practice guidelines for deployed medical personnel.