Hypocalcemia in Military Casualties From Point of Injury to Surgical Teams in Afghanistan

The Association of Calcium Derangements With 24-Hour Outcomes in the Deployed Combat Setting

INTRODUCTION

Calcium derangements remain poorly characterized in the combat trauma population. We describe the incidence of emergency department (ED) calcium derangements, associated physiologic derangements, and 24-hour mortality from the deployed combat setting.

MATERIALS AND METHODS

We analyzed adult casualties from 2007 to 2023 from the DoD Trauma Registry for U.S. military, U.S. contractor, and coalition casualties that had at least 1 ionized calcium value documented in the ED at a Role 2 or Role 3 military treatment facility. We constructed a series of multivariable logistic regression models to test for the association of hypocalcemia and hypercalcemia with physiological derangements, blood product consumption, and survival. Vital signs and other laboratory studies were based on the concurrent ED encounter.

RESULTS

There were 941 casualties that met inclusion for this analysis with 26% (245) having at least 1 calcium derangement. Among those, 22% (211) had at least 1 episode of hypocalcemia and 5% (43) had at least 1 episode of hypercalcemia in the ED. The vast majority (97%, 917) received calcium at least once. Median composite injury severity scores were lower among those with no calcium derangement (8 versus 17, P < .001). Survival was higher during the total hospitalization (98% versus 93%) among those with calcium derangements but similar at 24 hours (99% versus 98%, P = .059). After adjusting for confounder, any hypocalcemic measurement was associated with an elevated international normalized ratio (odds ratio 1.94, 95% CI 1.19-3.16), acidosis (1.66, 1.17-2.37), tachycardia (2.11, 1.42-3.15), hypotension (1.92, 1.09-3.38), depressed Glasgow coma scale (3.20, 2.13-4.81), elevated shock index (2.19, 1.45-3.31), submassive transfusion (3.97, 2.60-6.05), massive transfusion (4.22, 2.66-6.70), supermassive transfusion (3.65, 2.07-6.43), and all hospital stay mortality (2.30, 1.00-5.29). Comparatively, any hypercalcemic measurement was associated with acidosis (2.96, 1.39-6.32), depressed Glasgow coma scale (4.28, 1.81-10.13), submassive transfusion (3.40, 1.37-8.43), massive transfusion (6.25, 2.63-14.83), and supermassive transfusion (13.00, 5.47-30.85).

CONCLUSIONS

Both hypocalcemia and hypercalcemia in the ED were associated with physiological derangements and blood product use, with a greater extent observed in those with hypocalcemia compared to those with hypercalcemia. Prospective studies are underway to better explain and validate these findings.

Hypocalcaemia upon arrival (HUA) in trauma patients who did and did not receive prehospital blood products: a systematic review and meta-analysis

PURPOSE

Hypocalcaemia upon arrival (HUA) to hospital is associated with morbidity and mortality in the trauma patient. It has been hypothesised that there is an increased incidence of HUA in patients receiving prehospital transfusion as a result of citrated blood products. This research aimed to determine if there was a difference in arrival ionised calcium (iCa) levels in trauma patients who did and did not receive prehospital transfusion.

METHODS

We conducted a systematic review and meta-analysis of patients with an Injury Severity Score (ISS) > / = 15 and an iCa measured on hospital arrival. We then derived mean iCa levels and attempted to compare between-group variables across multiple study cohorts.

RESULTS

Nine studies reported iCa on arrival to ED, with a mean of 1.08 mmol/L (95% CI 1.02-1.13; I2 = 99%; 2087 patients). Subgroup analysis of patients who did not receive prehospital transfusion had a mean iCa of 1.07 mmol/L (95% CI 1.01-1.14; I2 = 99%, 1661 patients). Transfused patients in the 3 comparative studies had a slightly lower iCa on arrival compared to those who did not receive transfusion (mean difference - 0.03 mmol/L, 95% CI - 0.04 to - 0.03, I2 = 0%, p = 0.001, 561 patients).

CONCLUSION

HUA is common amongst trauma patients irrespective of transfusion. Transfused patients had a slightly lower initial iCa than those without transfusion, though the clinical impact of this remains to be clarified. These findings question the paradigm of citrate-induced hypocalcaemia alone in trauma. There is a need for consensus for the definition of hypocalcaemia to provide a basis for future research into the role of calcium supplementation in trauma.

Association of Non-Transfusion-Related Admission Hypocalcaemia With Haemodynamic Instability in Paediatric Major Trauma: A Retrospective Single-Centre Pilot Study

Background The 'lethal triad' of acidosis, hypothermia, and coagulopathy is now considered a diamond of death, with ionised hypocalcaemia (iHypoCa) contributing to cardiovascular decompensation and coagulopathy. iHypoCa may be associated with haemodynamic instability and adverse outcomes in paediatric major trauma patients. However, current data are limited. The primary aim of this pilot study was to report the association between admission iHypoCa and early hypotension on admission in a cohort of paediatric major trauma patients. Secondary aims include reporting the incidence and differential determinants of iHypoCa and the association with treatment (vasoactive agents, blood transfusion, interventional radiology (IR), or surgery) and adverse outcomes (length of stay, morbidity (Glasgow Outcome Scale), and mortality). Methods This pilot study is a retrospective analysis of paediatric major trauma patients (<16 years old) admitted to a major trauma centre (2016-2022). Patients with an admission ionised calcium level obtained before the administration of blood products were included. Multivariable logistic regression was used to assess the dichotomous endpoint of hypotension (systolic blood pressure of <80 mmHg for <1 year, <85 mmHg for one to five years, <90 mmHg for five to 12 years, <100 mmHg for >12 years) for association with hypocalcaemia and adjusted for other potential variables of interest (age, gender, Injury Severity Score, pre-hospital fluids, and acidosis). Results Admission iHypoCa was observed in 8/45 (17.8% (95% confidence interval (CI) 9.3-31.3%)) patients. Other than the adolescent age group (p < 0.05), there were no significant differences in the baseline characteristics. As a pilot study, this was not powered for statistical significance; however, point estimates of the odds of hypotension were almost three times higher for patients with iHypoCa (odds ratio (OR) 2.8 (95% CI 0.4-23.6), p = 0.33). An association between iHypoCa and the need for IR/surgery in the first 24 hours of admission was also observed (OR 10.9 (95% CI 1.4-159.4), p < 0.05). Conclusion iHypoCa was observed in approximately one in six paediatric major trauma patients at admission and may be associated with increased odds of requiring IR/surgery. Larger multicentre studies are required to clarify point estimates for treatment requirements and adverse outcomes.

Retrospective analysis of the effects of hypocalcemia in severely injured trauma patients

BACKGROUND

It has been suggested that the Lethal Triad be modified to include hypocalcemia, coined as the Lethal Diamond. Hypocalcemia in trauma has been attributed to multiple mechanisms, but new evidence suggests that traumatic injury may result in the development of hypoCa independent of blood transfusion. We hypothesize that hypocalcemia is associated with increased blood product requirements and mortality.

METHODS

A retrospective study of 1,981 severely injured adult trauma patients from 2016 to 2019. Ionized calcium (iCa) levels were obtained on arrival and subjects were categorized by a threshold iCa level of 1.00 mmol/L and compared. Univariable and multivariable logistic regression analysis was performed.

RESULTS

The hypocalcemia (iCa <1.00 mmol/L) group had increased rate of overall (p = 0.001), 4-hr (p = 0.007), and 24-hr (p = 0.003) mortality. There was no difference in prehospital transfusion volume between groups (p = 0.25). Hypocalcemia was associated with increased blood product requirements at 4 h (p <0.001), 24 h (p <0.001), and overall hospital length of stay (p <0.001). Logistic regression analysis showed increased odds of 4-hour mortality (OR 0.077 [95 % CI 0.011, 0.523], p = 0.009) and 24-hour mortality (OR 0.121 [95 % CI 0.019, 0.758], p = 0.024) for every mmol/L increase in iCa.

CONCLUSIONS

This study shows the association of hypoCa and traumatic injury. Severe hypoCa was associated with increased odds of early and overall mortality and increased blood product requirements. These results support the need for future prospective trials assessing the role of hypocalcemia in trauma.

Impact of Transfused Citrate on Pathophysiology in Massive Transfusion

This narrative review article seeks to highlight the effects of citrate on physiology during massive transfusion of the bleeding patient.

DATA SOURCES

A limited library of curated articles was created using search terms including "citrate intoxication," "citrate massive transfusion," "citrate pharmacokinetics," "hypocalcemia of trauma," "citrate phosphate dextrose," and "hypocalcemia in massive transfusion." Review articles, as well as prospective and retrospective studies were selected based on their relevance for inclusion in this review.

STUDY SELECTION

Given the limited number of relevant studies, studies were reviewed and included if they were written in English. This is not a systematic review nor a meta-analysis.

DATA EXTRACTION AND SYNTHESIS

As this is not a meta-analysis, new statistical analyses were not performed. Relevant data were summarized in the body of the text.

CONCLUSIONS

The physiologic effects of citrate independent of hypocalcemia are poorly understood. While a healthy individual can rapidly clear the citrate in a unit of blood (either through the citric acid cycle or direct excretion in urine), the physiology of hemorrhagic shock can lead to decreased clearance and prolonged circulation of citrate. The so-called "Diamond of Death" of bleeding-coagulopathy, acidemia, hypothermia, and hypocalcemia-has a dynamic interaction with citrate that can lead to a death spiral. Hypothermia and acidemia both decrease citrate clearance while circulating citrate decreases thrombin generation and platelet function, leading to ionized hypocalcemia, coagulopathy, and need for further transfusion resulting in a new citrate load. Whole blood transfusion typically requires lower volumes of transfused product than component therapy alone, resulting in a lower citrate burden. Efforts should be made to limit the amount of citrate infused into a patient in hemorrhagic shock while simultaneously addressing the induced hypocalcemia.

Biochemical disturbance in damage control resuscitation: mechanisms, management and prognostic utility

PURPOSE OF REVIEW

With advances in resuscitative techniques, trauma patients are surviving increasingly severe injuries and physiological insult. Timely recognition of futility remains important in terms of patient dignity and resource preservation yet is increasingly challenging in the face of these advances. The understanding of biochemical derangement from pathophysiological processes of trauma and iatrogenic effects of resuscitation has expanded recently.

RECENT FINDINGS

Acidosis and hypocalcaemia have been recognized as important contributors to mortality among trauma patients. Although less well recognized and studied, critical injury and high blood product volume resuscitation render patients vulnerable to life-threatening hyperkalaemia. The methods of correcting disruptions to acid-base and electrolyte homeostasis during damage control resuscitation have changed little recently and often rely on evidence from undifferentiated populations. Biochemical disturbances have value as ancillary predictors of futility in trauma resuscitation.

SUMMARY

These findings will contribute to a greater understanding among anaesthesiologists of the causative mechanisms and effects of biochemical derangement after severe injury and aid them in the delivery of well tolerated and effective damage control resuscitation. Gaps in the evidence base are highlighted to encourage future work.

Hypocalcemia as a predictor of mortality and transfusion. A scoping review of hypocalcemia in trauma and hemostatic resuscitation

Background

Calcium plays an essential role in physiologic processes, including trauma's “Lethal Diamond.” Thus, inadequate serum calcium in trauma patients exacerbates the effects of hemorrhagic shock secondary to traumatic injury and subsequently poorer outcomes compared to those with adequate calcium levels. Evidence to date supports the consideration of calcium derangements when assessing the risk of mortality and the need for blood product transfusion in trauma patients. This review aims to further elucidate the predictive strength of this association for future treatment guidelines and clinical trials.

Methods

Publications were collected on the relationship between i‐Ca and the outcomes of traumatic injuries from PubMed, Web of Science, and CINAHL. Manuscripts were reviewed to select for English language studies. Hypocalcemia was defined as i‐Ca <1.2 mmol/L.

Results

Using PRISMA guidelines, we reviewed 300 studies, 7 of which met our inclusion criteria. Five papers showed an association between hypocalcemia and mortality.

Conclusions

In adult trauma patients, there has been an association seen between hypocalcemia, mortality, and the need for increased blood product transfusions. It is possible we are now seeing an association between low calcium levels prior to blood product administration and an increased risk for mortality and need for transfusion. Hypocalcemia may serve as a biomarker to show these needs. Therefore, hypocalcemia could potentially be used as an independent predictor for multiple transfusions such that ionized calcium measurements could be used predictively, allowing faster administration of blood products.

The Role of Whole Blood Transfusions in Civilian Trauma: A Review of Literature in Military and Civilian Trauma

Resuscitation techniques for the management of adult trauma patients have evolved over the 20th century. Whole blood transfusions were previously used as the standard of care, whereas blood component therapy is the current method employed across most trauma centers across the United States. Prior to the transition, no studies were conducted to show improved efficacy of hemostatic potential in trauma patients. Recent conflicts in Iraq and Afghanistan have challenged the dogma that whole blood transfusions are not the standard of care and have shown potential as the superior transfusion product for adult trauma patients. The purpose of this review is to provide a comprehensive review and elucidate if whole blood transfusions have a role in civilian trauma patients based upon recent military medical literature and civilian pilot studies using whole blood transfusions.