Survival following Prehospital Traumatic Cardiac Arrest Resuscitation in the Israel Defense Forces: A Retrospective Study

Abstract

Background

Prehospital traumatic cardiac arrest (TCA) is associated with a poor prognosis and requires urgent interventions to address its potentially reversible causes. Resuscitative efforts of TCA in the prehospital setting may entail significant resource allocation and impose added tolls on caregivers. The Israel Defense Forces Medical Corps (IDF-MC) instructs clinicians to perform a set protocol in the case of TCA, providing prompt oxygenation, chest decompression and volume resuscitation. This study investigates the settings, interventions, and outcomes of TCA resuscitation by IDF-MC teams over 25 years in both combat and civilian settings.

Methods

Retrospective study of the IDF-MC Trauma Registry between 1997–2022. Search criteria were applied to identify cases where the TCA protocol was initiated. A manual review of cases matching the search criteria was performed by two curators to determine the indications, interventions, and outcomes of casualties with prehospital TCA. Patients for whom interventions were performed outside of the TCA protocol, such as with measurable vital signs, were excluded. The primary outcome was survival to hospital admission, with the secondary outcome being return of vital signs in the prehospital setting.

Results

Following case review, 149 patients with prehospital TCA were included, with a median age of 21 (interquartile range 19–27). Eighty-four (56.4%) presented with TCA in military or combat settings, with gunshot wounds and blast injuries being the most common mechanisms in this group. For 56 casualties (37.8%), all components of the protocol were performed (oxygenation, chest decompression, and volume resuscitation). Five (3.4%) casualties had return of vital signs in the prehospital setting, but none survived to hospital admission.

Conclusion

The prognosis of prehospital TCA is poor, and efforts to address its potentially reversible causes may often be futile. These notions may be further emphasized in military settings, where resources are limited, and extensive penetrating injuries are more common.

Introduction

Treatment of prehospital traumatic cardiac arrest (TCA) is centered on addressing potentially reversible etiologies (1–4). The utility of these efforts has long been debated, with reported survival rates for out-of-hospital TCA ranging between 0% (5) and 25% (6). When examining the current body of evidence on prehospital TCA, it is evident that survival and neurological outcomes are generally poor (1,2, 5). Potentially reversible causes of TCA include hypoxia, decompensated hemorrhagic shock, cardiac tamponade, and tension pneumothorax, and interventions in the setting of TCA aim to address these etiologies (2, 4). Accordingly, prehospital guidelines for TCA often include oxygenation, chest decompression (needle decompression and/or chest drain), and volume resuscitation (4).

The distinction between prehospital and in-hospital TCA protocols is important, due to contrasts in both diagnostic and therapeutic resources. Resuscitative efforts of trauma patients with TCA may entail significant resource allocation, and some have called for stricter criteria to withhold or terminate these often futile efforts in patients with loss of vital signs following trauma (5, 7). In the military setting, this issue becomes even more pronounced, as resuscitative interventions for casualties with TCA may come at the expense of treating other wounded personnel, endanger military missions, and subject medical personnel to added tolls. The consequences of futile measures for addressing TCA may also have ramifications in civilian settings, such as in mass casualty events where resource allocation is key.

The Israel Defense Forces Medical Corps (IDF-MC) provides prehospital trauma care for casualties injured in both military conflicts and peacekeeping missions. The IDF Trauma Registry (IDF-TR) has maintained relatively consistent guidelines for treating prehospital TCA over the last several decades, headlined by oxygenation, bilateral chest decompression, and infusion of fluids or blood products. In the currently published literature, data on the outcomes of military casualties with TCA are scarce and primarily entail accounts from military field hospitals and higher-role facilities (8,9). This study investigates the IDF experience with prehospital TCA over 25 years, aiming to describe the setting, interventions, and outcomes of interventions among casualties presenting with TCA in civilian and combat settings.

Methods

Study Design and Setting

Retrospective registry-based study using the IDF-TR. This study was approved by the IDF institutional review board (#1948–2018) and revised according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) recommendations. The IDF-TR was established in 1997 to document the treatment of prehospital trauma casualties treated by IDF advanced life support (ALS) teams, who provide point-of-injury and en-route care to both civilian and military casualties (10).Typical response intervals for casualties injured in military circumstances are several minutes, as teams are stationed in close proximity. Data documented in the IDF-TR are based on casualty cards filled out during prehospital treatment and additional information entered into a web-based digital platform made by ALS clinicians who attended the scene. Variables documented in the IDF-TR include casualty demographic data, scene data, injury mechanism, vital signs measurements, prehospital life-saving interventions, mode of evacuation, casualty urgency, and free-text descriptions of injuries and interventions. As previously described, postmortem data, including autopsy, postmortem computed tomography, and forensic pathologist reports are available and documented in the IDF-TR for some military fatalities (1).When sufficient data are available, injury survivability is remarked in these reports, based on the nature of injuries and assuming optimal care and resources. However, these determinations do not take into account the tactical scenario or transport interval.

To identify casualties who potentially exhibited prehospital TCA, we queried the database for cases matching any of nine criteria that may suggest TCA, between 1997–2022 (Supplementary appendix). These criteria were chosen to screen for casualties who exhibited loss of vital signs (i.e., documented heart rate or systolic blood pressure of 0), received interventions corresponding with the IDF-MC guidelines for TCA resuscitation (i.e., bilateral needle decompression), were pronounced dead on scene or during hospital transport by the IDF ALS clinician, or cases where free text description of injuries referred to prespecified keywords suggesting use of the TCA protocol. Cases matching the registry search criteria where interventions were made in the presence of vital signs (i.e., needle decompression to address hemodynamic compromise following chest injury) were excluded, as these were not TCA interventions. Each of the identified cases was then reviewed by two authors (TT, OA) who are medical officers at the IDF Trauma and Combat Medicine Branch, responsible for investigating cases of prehospital trauma and composing the IDF-MC prehospital guidelines for trauma. Following an independent review of cases by each of the two authors, any discrepancies were resolved through discussion, until a consensus was reached. The primary outcome of the study was survival to hospital admission, with the secondary outcome being a return of vital signs after intervention. The manual review of cases was performed to determine the following:

1. Does the case describe TCA?

2. Was the arrest witnessed or unwitnessed?

3. Did the team perform an airway intervention (i.e., bag-mask ventilation, endotracheal intubation, cricothyroidotomy)?

4. Did the team perform a chest intervention (i.e., needle decompression, chest tube placement)?

5. Did the team administer volume resuscitation (i.e., crystalloids, freeze-dried plasma, packed red blood cells, whole blood)?

6. Was the TCA protocol fully completed (i.e., airway intervention, chest intervention, and volume resuscitation)?

7. Were chest compressions performed?

8. Was there a return of vital signs (i.e., palpated pulse)? Did the patient survive to hospital admission?

9. Was TCA intervention indicated according to the prehospital guideline?

10. Was the injury deemed survivable according to postmortem evaluation?

11. What was the interval between the reported time of injury and the arrival of the first ALS team on scene?

Data from the review process were joined with data directly extracted from the IDF-TR to complete the dataset for statistical analysis. Injury survivability was determined in cases when postmortem assessment was documented in the IDF-TR, as has been previously described (11).

IDF-MC Clinical Practice Guidelines for TCA

During the study period, the IDF-MC treatment algorithm for TCA has recommended initial assessment of a palpable pulse, breathing, spontaneous body movement, and pupil reaction to light when suspecting a loss of vital signs following trauma. When all the above are absent and arrest was witnessed or reported up to 5 min before the arrival of an ALS clinician, the protocol calls for initiation of the TCA protocol, aimed at addressing its potentially reversible causes. The recommended interventions include oxygenation and ventilation (bag-mask ventilation, endotracheal intubation, or cricothyroidotomy), bilateral chest decompression (needle decompression or chest tube placement), and administration of one unit of the best resuscitation fluid available to the team (whole blood, freeze-dried plasma, or crystalloids). Volume resuscitation can be administered via either intravenous (IV), or intraosseous (IO) access when IV access is unsuccessful or deemed improbable by the ALS clinician. Several IO devices have been used by the IDF-MC during the study period, and the proximal tibia is recommended as the preferred site for IO access. Reassessment is performed following the completion of these interventions, or 15 min after the first intervention. The IDF-MC protocol has instructed against chest compressions in TCA and forbids thoracotomy, pericardiocentesis, or other surgical interventions in the prehospital setting (Figure 1).

Figure 1. Traumatic cardiac arrest algorithm in the Israel Defense Forces Medical Corps of 2023.

In 2021, an update to the prehospital guideline was introduced, recommending bag-mask ventilation, bilateral needle decompression, and infusion of a single unit of the best resuscitative fluid, prior to reassessment. The main consideration behind this change, which omitted mandatory definitive airway establishment and bilateral chest tube placement, was to expedite the protocol and potentially better address the key etiologies of traumatic TCA. Figure 1 depicts the currently recommended protocol in the IDF-TR.

Statistical Analysis

Continuous variables are described as medians and interquartile ranges (IQR) with categorical variables described as n (%). Comparison of categorical variables was performed using chi-square and Fisher’s exact tests, while quantitative variables were compared using the Kruskal-Wallis test. A priori, we intended to apply multivariable logistic regression to identify independent factors related to injury mechanisms and interventions associated with survival following TCA treatment. However, this analysis was omitted due to the rarity of the primary outcome in our dataset. p values of less than 0.05 were considered statistically significant for all statistical tests. Statistical analyses were performed using R software version 4.2.1.

Results

Study Population Characteristics

Overall, 285 cases matching the queried criteria were identified in the IDF-TR between 1997 and 2022. Upon manual review, we excluded cases where vital signs were undocumented but intact according to free-text case description (n = 79), cases where interventions were performed as part of the chest trauma protocol (n = 42; i.e., needle decompression for suspected tension pneumothorax), cases where documentation was insufficient to determine TCA protocol activation (n = 12), and cases where the TCA protocol was initiated before the loss of vital signs (n = 3). Therefore, 149 (52.3%) cases of prehospital TCA protocol resuscitation were identified and included in the analyses (Figure 2). The median age was 21 years (IQR 19–27), 133 (89.9%) were male, and 84 (56.4%) sustained traumatic injuries in military settings. The most common injury mechanisms in the entire cohort were motor vehicle collision (63.1%) and gunshot (16.9%). In military settings, the most common mechanisms were gunshot (64.3%) and blast (17.9%). Penetrating injuries were more common among casualties of military events (85.7%) as compared with nonmilitary settings (p < 0.001). The most commonly injured regions were the torso (64.4% of casualties) and head (24.2%), with the latter being significantly more common in nonmilitary events (military:10.7%, nonmilitary: 41.5%; p < 0.001). The median interval from the first report of injury to the arrival of the first ALS team was 11 min (IQR 5–18.75), with no significant differences between military and nonmilitary events (p = 0.31). Loss of vital signs during ALS team treatment (witnessed arrest) was more frequent in military settings (48.8%) than in nonmilitary settings. Table 1 details the demographic and injury characteristics of the study population.

Figure 2. Flow diagram of casualties included in the study. IDF-TR: Israel Defense Forces Trauma Registry; TCA: traumatic cardiac arrest.

Table 1. Demographics and injury characteristics of the study population undergoing TCA resuscitation.

	Study population by event type
	Nonmilitary event	Military event	Total	p-value^a
	(N = 65)	(N = 84)	(N = 149)
Age – Median (IQR), years	21 (19–31)	21 (19–25)	21 (19–27)	0.491
Missing	26	29	55
Sex – N (%)
Male	57 (89.1)	76 (90.5)	133 (89.9)	0.790
Missing	1	0	1
Body region involvement – N (%)
Head	27 (41.5)	9 (10.7)	36 (24.2)	<0.001
Face	10 (15.4)	5 (6.0)	15 (10.1)	0.097
Neck	2 (3.1)	9 (10.7)	11 (7.4)	0.114
Upper extremity	10 (15.4)	18 (21.4)	28 (18.8)	0.402
Torso	44 (67.7)	52 (61.9)	96 (64.4)	0.494
Pelvis	2 (3.1)	7 (8.3)	9 (6.0)	0.300
Lower extremity	14 (21.5)	17 (20.2)	31 (20.8)	0.842
Penetrating injury – N (%)	20 (30.8)	72 (85.7)	92 (61.7)	<0.001
Mechanism of injury – N (%)
Blast	0 (0.0)	15 (17.9)	15 (10.1)	<0.001
Fall	3 (4.6)	1 (1.2)	4 (2.7)
Gunshot	11 (16.9)	54 (64.3)	65 (43.6)
Motor vehicle collision	41 (63.1)	6 (7.1)	47 (31.5)
Other	6 (9.2)	7 (8.3)	13 (8.7)
Shrapnel	1 (1.5)	1 (1.2)	14 (8.7)
Blunt object strike	3 (4.6)	0 (0.0)	15 (8.7)
Interval from report of injury to arrival of first ALS team on-scene – Median (IQR), minutes	11 (4–16)	12 (5–20)	11 (5–18.75)	0.311
Missing	10	17	27
Timing of arrest – N (%)
Witnessed by ALS team	20 (30.8)	41 (48.8)	61 (40.9)	0.010
Unwitnessed	39 (60.0)	42 (50.0)	81 (54.4)
Could not be determined	6 (9.2)	1 (1.2)	7 (4.7)
Indication for intervention – N (%)
Indicated according to TCA protocol	39 (65.0)	65 (80.2)	104 (73.8)	<0.001
Unindicated due to arrival >5 min after loss of signs	18 (30.0)	11 (13.6)	29 (20.6)	0.133
Could not be determined	2 (3.3)	4 (4.9)	6 (4.3)	<0.001
Unindicated due to injuries incompatible with life	1 (1.7)	1 (1.2)	2 (1.4)	<0.001
Injury survivability according to postmortem report – N (%)
Could not be determined/undocumented	41 (63.1)	43 (51.2)	84 (56.4)	<0.001
Non-survivable	24 (36.9)	38 (45.2)	62 (41.6)
Survivable	0 (0.0)	3 (3.6)	3 (2.0)

^ap values acquired from Fisher’s exact test, Kruskal-Wallis test, or chi-square test.

ALS – advanced life support, IQR – interquartile range, TCA – traumatic cardiac arrest.

Prehospital Traumatic Cardiac Arrest Interventions

The interventions performed as part of TCA treatment among the study population are detailed in Table 2. Overall, the ALS clinicians completed the full TCA protocol, including airway support, chest decompression (either needle decompression or thoracostomy), and volume resuscitation for 56 (37.8%) casualties, with no significant differences between military and nonmilitary settings.

Table 2. Prehospital traumatic cardiac arrest interventions and injury characteristics of the study population.

	Study population by event type
	Nonmilitary event	Military event	Total	p-value^a
	(N = 65)	(N = 84)	(N = 149)
Completed full protocol (Airway/ventilation, chest decompression and volume resuscitation)	24 (37.5)	32 (38.1)	56 (37.8)	1.000
Airway management/ventilation – N (%)
Any airway management	62 (95.4)	77 (91.7)	139 (93.3)	0.514
Bag mask ventilation	33 (50.8)	32 (38.1)	65 (43.6)	0.136
Endotracheal intubation	50 (76.9)	66 (78.6)	116 (77.9)	0.844
Cricothyroidotomy	8 (12.3)	11 (13.1)	19 (12.8)	1.000
Chest decompression – N (%)
Any chest decompression procedure	64 (98.5)	84 (100.0)	148 (99.3)	0.436
Needle application	56 (86.2)	70 (83.3)	126 (84.6)	0.820
Chest tube	26 (40.0)	46 (54.8)	72 (48.3)	0.098
Volume resuscitation – N (%)
Any volume resuscitation	25 (39.1)	37 (44.0)	62 (41.9)	0.615
Crystalloids	13 (20.0)	22 (26.2)	35 (23.5)	0.438
Freeze-dried plasma	9 (13.8)	12 (14.3)	21 (14.1)	1.000
Packed red blood cells	0 (0.0)	6 (7.1)	6 (4.0)	0.036
Whole blood	3 (4.6)	4 (4.8)	7 (4.7)	1.000
Intravenous access	38 (58.5)	44 (52.4)	82 (55.0)	0.509
Intraosseous access	17 (26.2)	25 (29.8)	42 (28.2)	0.715
Other prehospital interventions – N (%)
Tourniquet application	2 (3.1)	10 (11.9)	12 (8.1)	0.068
Tranexamic acid	9 (13.8)	14 (16.7)	23 (15.4)	0.404
Evacuation – N (%)
Air medical evacuation	6 (9.2)	18 (21.4)	24 (16.1)	0.071
Return of vital signs and survival – N (%)
≥1 vital sign^ˠ	1 (1.6)	4 (4.9)	5 (3.4)	<0.001
Survived to hospital admission	0 (0.0)	0 (0.0)	0 (0.0)	–

^ap values acquired from Fisher’s exact test, Kruskal-Wallis test or chi-square test.

^ˠ Refers to palpated pulse/spontaneous breathing/pupil reaction/measurable blood pressure.

Airway management or bag-mask ventilation was performed among 93.3% of all casualties, with 116 (77.9%) undergoing endotracheal intubation. Chest decompression was performed for 139 (99.3%) casualties as part of the resuscitative efforts, with 126 (84.6%) undergoing needle decompression. IV access was established in 55% of cases and IO access in 28.2%. Volume resuscitation was administered for 62 (41.9%) casualties, with the most frequently used fluids being crystalloids (n = 35; 23.5%), freeze-dried plasma (n = 21; 14.1%), and whole blood (n = 7, 4.7%).

Outcomes, Indications, and Survivability

Overall, five (3.4%) casualties had return of one or more vital signs during prehospital treatment following TCA. Table 3 details the injury characteristics, interventions, and known outcomes for these five casualties. None of the casualties survived, with all being declared dead prior to hospital arrival.

Table 3. Description of casualties with return of vital signs during traumatic cardiac arrest treatment.

Case	Age	Sex	Injury setting	Trauma mechanism	Injury description	Loss of vital signs description	TCA interventions	Return of vital signs description*	Outcome	Postmortem report	Injury survivability
1	20	Male	Military – combat	Gunshot wound	Single gunshot wound in the left upper hemithorax.	Upon initial examination at the point-of-injury: Unconscious, pale, apneic, no palpable pulse, dilated pupils.	Airway: Endotracheal intubation Chest: Unilateral needle decomplression, followed by chest tube placement draining large volumes of blood Volume: 500 ml crystalloids via intarosseus access	Return of palpable carotid pulse several minutes following needle decompression	Declared dead prior to hospital arrival	Massive hemopneumothorax, lung laceration, pericardial laceration	Non-survivable
2	36	Male	Military – combat	Gunshot wound	Single gunshot wound through upper back and neck.	Upon initial examination following evacuation from point-of-injury to forward medical team: Unconscious, apneic with no palpable pulse.	Airway: Cricothyroidotomy Chest: Bilateral needle decomplression, followed by bilateral chest tube placement draining large volumes of blood from left hemithorax Volume: 500 ml crystalloids and 1 g of tranexamic acid via intraosseus access	Return of "color" to the patient’s face and palpable carotid pulse following needle decompression	Declared dead during air medical evacuation to hospital	Massive hemopneumothorax, emphysema of soft tissues in the neck area, pneumomediastinum, sharpnel induced laceration of lung	Potentially survivable
3	20	Male	Military – terror attack	Gunshot wound	Gוunshot wound with entry in the scapular area and exit in the left hemithorax.	Upon initial examination at point-of-injury: Glasgow Coma Scale score 12, tachycardic (120 beats per minute), and tachypneic with uneven lung expansion, peripheral cyanosis. After several minutes loss of palpable pulse and visible breathing.	Airway: Bag-mask ventilation followed by endotracheal intubation Chest: Unilateral needle decompression in left hemithorax (x2) Volume: 500 ml crystalloids and 1 g of tranexamic acid via intraosseus access	Return of weakly palpable pulse during interventions, followed by second loss of vital signs.	Declared dead prior to hospital arrival	N/A	N/A
4	19	Male	Civilian	Blunt trauma in motor vehicle accident	Blunt chest and abdominal trauma following high speed collision	Upon initial examination at point-of-injury: Unresponsive, carotid pulse of 140 beats per minute, tachypneic (40 breaths per minute). Loss of vital signs during assessment.	Airway: Bag mask ventilation with oxygen Chest: Unilateral needle decompression in left hemithorax (x2) Volume: 500 ml crystalloids and 1 g of tranexamic acid via intravenous access	Return of palable pulse and blood pressure measurment 135/80 mmHg, oxygen saturation of 93%, followed by second loss of vital signs.	Declared dead prior to hospital arrival	N/A	N/A
5	43	Male	Military – training	Helicopter crash	Blunt multisystem trauma in head, neck upper limbs, chest and lower limbs.	Upon initial examination at point-of-injury: Unresponsive, no palpable pulse or visible breathing, dilated pupils.	Airway: Cricothyroidotomy Chest: Unilateral chest tube placement. Volume: N/A	Return of pupil constriction according to team.	Declared dead prior to hospital arrival	Massive intracranial bleeding (subarachnoid), fractures of cranial, facial, chest, and pelvic bones.	Non-survivable

*Data ascertained from review of cases in the IDF-TR.

When assessing the indications for intervention according to the TCA protocol, we determined that treatment was indicated among 104 (73.8%) casualties. Arrival more than 5 min after loss of vital signs, which constitutes a contraindication to treatment according to the IDF-MC protocol, was identified in 30% of cases in nonmilitary settings and 13.6% of cases occurring in military settings. Postmortem computed tomography or autopsy reports were unavailable for most casualties. Among casualties for whom injury survivability was reported in the postmortem assessment (n = 62), potentially survivable injuries were noted in only three cases (4.8%). Further investigation of these cases revealed that two resulted from traumatic asphyxia after the collapse of a multistory building, and one from multiple penetrating shrapnel injuries to the thorax, abdomen, and limbs with no specific cause of death determined.

Discussion

This study presents the prehospital interventions and outcomes of casualties with traumatic cardiac arrest treated in both military and nonmilitary settings. Return of vital signs during TCA intervention was rare (3.4%), with no casualty surviving to reach hospital admission. The results of this study suggest that prehospital TCA presents a dire prognosis, and current efforts applied by prehospital clinicians are often ineffective. These observations may advise changes in criteria for withholding resuscitation in TCA and help prioritize prehospital interventions to address possibly reversible causes of TCA.

None of the casualties included in our cohort survived following TCA, which differs from previous reports and experience of other prehospital emergency medical services (EMS). In a recent study describing 915 TCA casualties treated by Dutch helicopter EMS, 3.9% of patients survived through hospital discharge (2). Duchateau et al. (12) reported 11% survival through discharge among 88 patients with TCA treated by French EMS. In the recently published meta-analysis by Vianen et al. (1), aggregating 36 studies, overall survival was 3.8%. To the best of our knowledge, only one previously published study reported no survival in a cohort of patients with prehospital TCA (5). The absence of survivors in our study may be attributed to the nature of the injuries along with the setting and extent of TCA interventions.

In this current study, 56.4% of injuries occurred in military settings, and 85.7% of these casualties sustained penetrating injuries, with blast and gunshot injuries accounting for over half of all cases of TCA. In comparison, penetrating injuries constituted approximately 15% of all cases in the Dutch HEMS study (2). As reported by Eastridge et al. (13), blast and gunshot injuries have become the predominant causes of mortality in military trauma and cause extensive and severe injuries. TCA survival following these injuries may thus be much lower than reported in previous studies, most of which document survival in civilian EMS settings (1). Of casualties with detailed postmortem reports, only three of 62 (4.8%) were deemed to sustain potentially survivable injuries, emphasizing the extent of injuries. The rate of witnessed arrest and interval from report to arrival of the first ALS team (median 11 min) in our cohort exemplifies the typically short arrival times of IDF ALS teams. Thus, many of the casualties in our cohort likely experienced TCA within minutes of injury, a scenario which may be less common in other TCA cohorts and would result in death before medical intervention. The exclusion of cases where the TCA protocol was activated prior to loss of vital signs, presumably in the peri-arrest period, may also contribute to the lack of survivors, as aggressive resuscitative measures applied in the peri-arrest period may yield better outcomes (14). Finally, the occurrence of most injuries in military settings may have affected the ability of clinicians to adequately perform the TCA resuscitation protocol, with outcomes also being affected by prolonged evacuation intervals to definitive care.

Although specific lifesaving procedures have not been associated with increased survival in TCA (15), we cannot rule out the potential effect of incomplete TCA protocol execution and unindicated resuscitation (22% of cases), as observed in our results. Only 37.8% of casualties received all components of our TCA protocol, with volume resuscitation most frequently absent. The relatively infrequent administration of volume resuscitation can be explained by several factors. First, the IDF TCA protocol is time-limited (15 min followed by reassessment) and dictates addressing the airway, performing bilateral chest decompression, and administering volume. As such, clinicians may have been unable to complete all interventions and chose to forego the volume component of the protocol. An additional explanation is a difficulty in establishing vascular access in cases of TCA, as has been demonstrated in non-traumatic cardiac arrest, or alternatively, allocating this task to less experienced clinicians to prioritize other interventions (16). Seeing as hemorrhage is the leading cause of preventable death due to trauma (13), prioritizing volume resuscitation as the initial intervention for prehospital TCA may be warranted, to address critical exsanguination and decreased preload caused by cardiac tamponade and tension pneumothorax. Intraosseous access may also be recommended as the default choice in these cases, considering the potential difficulty of establishing peripheral IV access. Additionally, we cannot rule out difficulties dictated by the operational circumstances or austere settings encountered by teams at the point of injury.

The criteria and interventions outlined in TCA protocols used by different EMS and military organizations vary widely. A recent study assessed TCA protocols across the US, finding 16 different TCA protocols with substantial variations in criteria for termination and recommended treatments (6). Notable measures absent from our TCA protocol but frequently recommended include chest compressions, administration of epinephrine or tranexamic acid, application of a pelvic binder, and resuscitative thoracotomy (4, 6, 17,18). The role of chest compressions, in particular, has been a topic of debate in the literature concerning TCA, due to the contrasts in pathophysiology from non-traumatic cardiac arrest (1, 4, 17). External chest compressions may be insufficient in addressing the potentially reversible causes of TCA and delay more critical interventions (19). However, further research is needed to establish their potential role in specific sub-populations, such as patients with TCA following blunt injury (4, 19). Although tourniquets are widely used in military settings to control extremity hemorrhage (20), their role in the setting of traumatic cardiac arrest has also been discussed (1). The limited use of tourniquets in this study may potentially be explained by the absence of active external bleeding, corresponding with the severe condition of casualties who were often assessed following arrest. Importantly, tourniquets or other hemorrhage control techniques should be promptly applied if a return of spontaneous circulation is achieved and external bleeding is observed. Future studies should seek to evaluate the effects of different interventions on TCA survival, in order to prioritize and focus clinician efforts.

Withholding or terminating resuscitation is a complex and highly emotional decision, which may be further amplified on the battlefield (7, 21). In austere military environments, resources are limited, with treatment and evacuation of patients often posing a danger to personnel involved and coming at the expense of other casualties. Accordingly, decision-making in these settings must abide by clear criteria for initiating, terminating, and withholding TCA interventions. The National Association of EMS Physicians 2013 position statement (7) stresses the balance between resource allocation and performing extensive interventions to achieve rare cases of survival in TCA. Our current protocol outlines clear criteria for initiating the TCA protocol, considering the timing of arrest and injury mechanisms. Decision-making in such cases may be further augmented by tools such as ultrasonography, which has been used to distinguish between TCA etiologies (4), but could foremost serve to identify cases where efforts may be futile (i.e., lack of cardiac motion with no apparent tamponade).

Higher-echelon military medical facilities may dictate alternative TCA intervention protocols with different inclusion criteria and more extensive interventions. More robust resources and specialized staff may give rise to higher survival rates, thus justifying TCA resuscitation. Smith et al. (21) argued that although much evidence has pointed toward the futility of TCA resuscitation, outcomes among military casualties arriving at deployed resuscitation facilities may be improved. Barnard et al. (8) surveyed the UK Joint Trauma Registry, finding 424 patients with TCA and a survival to discharge rate of 10.6%. As such, TCA protocols should be adapted to be better suited for the capabilities and resources of higher echelons of military medical care.

This study strengthens the recognized need for advanced measures to address the rapid deterioration of trauma patients in the prehospital setting. Recent studies have discussed the role of resuscitative thoracotomy (18, 22) and resuscitative endovascular balloon occlusion of the aorta (REBOA) (23,24) in trauma patients who are deemed to be on the cusp of arrest and rapidly deteriorating. Prehospital resuscitative thoracotomy in trauma patients with impending arrest may facilitate control of intrathoracic hemorrhage and release of cardiac tamponade (18), which Morton et al. (22) reported in both penetrating and blunt trauma patients undergoing prehospital thoracotomy. REBOA, on the other hand, could be effective in cases of rapid exsanguination from subdiaphragmatic hemorrhage (24). The adoption of these procedures in the point-of-injury military setting currently lacks ample evidence, and as suggested by Monchal et al. (18), should initially be evaluated in forward medical facilities with highly specialized and experienced staff.

Limitations

Our study is limited by several factors. First, this is a registry-based study and may thus be limited by partial or missing data, potentially affecting the inclusion of cases and outcomes reported in this study. Second, although we acknowledge that both scene interval and transport interval of casualties are important factors to consider in assessing the outcomes of traumatic cardiac arrest, we are unable to reliably report these for much of the cohort. Regrettably, the IDF-TR dataset often lacks complete timestamped information, particularly for scene and transport intervals throughout the study period. This issue is further compounded in cases of events occurring in military circumstances where scenes are often complex, and routine documentation of times is challenging. In contrast, the time of injury and time of arrival of medical teams are recorded for most events, which enabled reporting of the interval between injury and team arrival as presented in this study. Third, our methodology and criteria for identifying cases of TCA relied on identifying interventions included in the protocol and may thus have been unable to identify cases with insufficient documentation or cases where alternative interventions were initiated outside of the protocol. Fourth, since postmortem reports were unavailable for more than half of the casualties, the determination of survivability and fatal injuries was limited. Finally, since the manual case review also drew conclusions from free-text documentation, we cannot exclude clinician or curator bias.

Conclusions

Survival of trauma patients suffering from prehospital TCA amongst military and nonmilitary casualties is poor, and resuscitative interventions in prehospital military settings may be ineffective. Prehospital protocols for TCA should target specific subpopulations that can benefit from prompt interventions, prioritizing the potentially reversible causes of arrest. In limited resource settings, such as mass casualty incidents or military operations, TCA resuscitation should be carefully considered, as it may come at the expense of other casualties.

Disclosure statement

This study was performed as part of the Israel Defense Forces Trauma and Combat Medicine Branch efforts to improve the quality of combat casualty care, and received no external funding or support.