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Introduction Hypocalcemia at hospital presentation is associated with increased mortality in trauma patients with hemorrhagic shock. The 2019 updates to the Joint Trauma System Damage Control Resuscitation (DCR) Clinical Practice Guideline recommend calcium supplementation for ionized calcium (iCa) measurements <1.2 mmol/L. Ionized calcium goals for en route critical care (ERCC) following DCR are less defined, and the impact of in-flight hypocalcemia events among critically injured combat wounded is unknown. This study aimed to describe the association between hypocalcemia and mortality for combat-wounded with brain injury and polytrauma requiring transport by Critical Care Air Transport Teams (CCATT). Methods We performed a secondary analysis of a retrospective cohort of patients with moderate-to-severe traumatic brain injury transported by CCATT out of combat theater between January 2007 and May 2014. Additional inclusion criteria included polytrauma and at least one documented in-flight iCa measurement. We categorized exposures based on the minimum in-flight iCa measurement as severe hypocalcemia (iCa <0.9 mmol/L), hypocalcemia (iCa 0.9-1.11 mmol/L), and never hypocalcemic (iCa ≥1.12 mmol/L). The primary outcome measure was mortality. We calculated descriptive statistics and performed multivariate logistic regression to assess the association between hypocalcemia and mortality. Results We analyzed 190 subjects, with a median age of 24 years (interquartile range [IQR] 21 to 29 years) and 97.7% male gender. Explosive injuries (82.1%) and gunshot wounds (6.3%) were the most common mechanisms of injury. The median injury severity score was 34 (IQR 27 to 43). During the flight, 11.6% of patients had severe hypocalcemia, and 39.5% had hypocalcemia. Among patients with any hypocalcemia measurement in-flight (n = 97), 41.2% had hypocalcemia on pre-flight iCa, 28.9% received blood products in-flight, and 23.7% received in-flight calcium supplementation. Only 32.4% of patients with hypocalcemia or severe hypocalcemia in the setting of vasopressor administration received in-flight calcium supplementation. There was no significant difference in mortality between severe hypocalcemia (9.1%), hypocalcemia (5.3%), and never hypocalcemic (3.2%) patients even after controlling for pre-flight variables. Conclusion In-flight hypocalcemia events were common among critically ill combat-wounded polytrauma patients transported by CCATT but were not associated with differences in mortality. Future training should emphasize the need for calcium correction among ERCC patients requiring vasopressors. Future studies with larger sample sizes of patients receiving ERCC are needed to assess the association between in-flight calcium supplementation with clinical outcomes.

Introduction According to the Military Health System Traumatic Brain Injury (TBI) Center of Excellence, 51,261 service members suffered moderate to severe TBI in the last 21 years. Moderate to severe TBI in service members is usually related to blast injury in combat operations, which necessitates medical evacuation to higher levels of care. Prevention of secondary insult, and mitigation of the unique challenges associated with the transport of TBI patients in a combat setting are important in reducing the morbidity and mortality associated with this injury. The primary goal of this study was a secondary analysis comparing the impact of time to transport on clinical outcomes for TBI patients without polytrauma versus TBI patients with polytrauma transported out of the combat theater via Critical Care Air Transport Teams (CCATT). Our secondary objective was to describe the occurrence of in-flight events and interventions for TBI patients without polytrauma versus TBI with polytrauma to assist with mission planning for future transports. Materials and Methods We performed a secondary analysis of a retrospective cohort of 438 patients with TBI who were evacuated out of theater by CCATT from January 2007 to May 2014. Polytrauma was defined as abbreviated injury scale (AIS) of at least three to another region in addition to head/neck. Time to transport was defined as the time (in days) from injury to CCATT evacuation out of combat theater. We calculated descriptive statistics and examined the associations between time to transport and preflight characteristics, in-flight interventions and events, and clinical outcomes for TBI patients with and without polytrauma. Results We categorized patients into two groups, those who had a TBI without polytrauma (n = 179) and those with polytrauma (n = 259). Within each group, we further divided those that were transported within 1 day of injury, in 2 days, and 3 or more days. Patients with TBI without polytrauma transported in 1 or 2 days were more likely to have a penetrating injury, an open head injury, a preflight Glascow Coma Score (GCS) of 8 or lower, and be mechanically ventilated compared to those transported later. Patients without polytrauma who were evacuated in 1 or 2 days required more in-flight interventions compared to patients without polytrauma evacuated later. Patients with polytrauma who were transported in 2 days were more likely to receive blood products, and patients with polytrauma who were evacuated within 1 day were more likely to have had at least one episode of hypotension en route. Polytrauma patients who were evacuated in 2–3 days had higher hospital days compared to polytrauma with earlier evacuations. There was no significant difference in mortality between any of the groups. Conclusions In patients with moderate to severe TBI transported via CCATT, early evacuation was associated with a higher rate of in-flight hypotension in polytrauma patients. Furthermore, those who had TBI without polytrauma that were evacuated in 1–2 days received more in-flight supplementary oxygen, blood products, sedatives, and paralytics. Given the importance of minimizing secondary insults in patients with TBI, recognizing this in this subset of the population may help systematize ways to minimize such events. Traumatic Brain Injury patients with polytrauma may benefit from further treatment and stabilization in theater prior to CCATT evacuation.