Main findings
The management of traumatically injured patients in combat settings has advanced considerably during the past two decades.71–73 The TCCC guidelines introduced standard practices focusing on point of injury/prehospital care, and en route care, therefore providing deployed healthcare workers with a framework to provide optimal care.74 In summary, the main findings of each of the MARCH components in the military and civilian prehospital settings were: (1) Massive hemorrhage: current evidence on tourniquets and hemostatic agents was of low quality. However, in the included studies, tourniquets provided bleeding control with consequent hemodynamic improvement. There is a paucity of high-quality clinical literature supporting the use of one type of hemostatic dressing over another in humans. (2) Airway: studies investigating various methods of airway management, such as laryngoscope, GlideScope, LMA, and cricothyrotomy, were also of low quality. Overall, these procedures had high success rates with better patient outcomes when performed en route to hospital. (3) Respiratory management: the evidence was also of low quality. Studies reported high failure rates of prehospital needle decompression. (4) Circulation: studies were of higher quality overall compared with the other MARCH domains and assessed prehospital blood products and TXA administration. However, studies assessing prehospital blood transfusion had conflicting results. Studies conducting adjusted analyses reported better outcomes with blood product transfusion compared with crystalloids. Non-randomized data assessing prehospital TXA use did not report improved outcomes. (5) Hypothermia prevention: studies had low methodological quality. However, all methods used to treat hypothermia were efficacious to maintain or increase body temperature measured on arrival to the receiving facility.
Knowledge gaps
Through evaluating current literature, an important knowledge gap was identified; while TCCC guidelines were developed to be applicable to all prehospital/combat environments, there is a paucity of MARCH intervention studies conducted in cold environments. This gap is significant, as it is vital to ensure that while working to minimize the effects of hypothermia for the casualty, it is equally important to ensure that any MARCH intervention remains effective in extreme cold conditions. The evidence focusing on hypothermia prevention is robust; however, very few studies investigating these interventions were conducted in the cold. Notably, the two studies investigating hypothermia prevention interventions identified through this review were of limited quality and were not conducted in a cold environment.62 63 These considerations raise important questions within each component of the MARCH interventions: (1) How do the physiological changes of hypothermia impact massive hemorrhage control? (2) Will below freezing temperatures impact respiratory interventions should the condensation freeze? (3) At what rates and temperatures do crystalloids and blood products freeze? Most countries with active military operations reach a wide range of temperatures; it is therefore vital for future research to investigate the efficacy of the MARCH interventions in colder environments, such that the TCCC guidelines can be expanded on to specifically combat the effects of cold environments, such as poor weather and icy conditions.75
We think that some of the evidence identified in the in-hospital setting may be transferable and adapted to the prehospital setting, such as the use of gum elastic bougie for endotracheal intubation. Few RCTs have been performed in ED and OR settings to evaluate the efficacy of bougies and stylets76–79; only one RCT compared the efficacy of an endotracheal tube introducer versus standard orotracheal intubation, reporting higher overall success rates and higher percentage of intubating difficult laryngeal views on first attempts in the endotracheal introducer group.80 One study assessed these techniques in the prehospital setting.81 Of these, a trial conducted in the ED reported significantly higher first-attempt intubation success using a tracheal tube introducer (bougie) versus an endotracheal tube with a stylet.76 In the prehospital setting, a recent retrospective review evaluated the variables associated with successful definitive airways in traumatically injured patients, and reported bougie use as one of the factors significantly associated with increased success rates.82 We think that these techniques are likely able to be adapted to prehospital settings, including austere and cold environments. However, future research is warranted.
In 2018, the finger thoracostomy (FT) was introduced to the TCCC guidelines as an additional treatment option for a suspected tension pneumothorax after two failed needle decompression attempts for combat casualties in refractory shock.83 One recent retrospective cohort study evaluated the efficacy of FTs in a helicopter emergency medical service (HEMS) setting, and reported a low complication rate in comparison to the needle decompression method.84 Additionally, in 2019, the iTClamp (Innovative Trauma Care, Edmonton, Alberta) was introduced in the TCCC guidelines in the management of craniomaxillofacial (CMF) injuries and penetrating neck injuries.85 The guidelines recommend the iTClamp be used as a primary treatment modality along with a TCCC-recommended hemostatic dressing and direct manual pressure. One case series investigating the efficacy of the iTClamp in the prehospital setting reported that 87.5% of cases (n=70) achieved adequate CMF hemorrhage control.86 Therefore, further research is warranted exploring the efficacy of these added interventions in all combat and austere environments.
In the military prehospital setting, blood transfusion has been widely studied leading to the adoption of blood product transfusion into civilian prehospital care.87 88 Through the literature identified in this review, studies assessing blood transfusion were of higher quality, though some reported conflicting results. Studies assessing mortality in this population are typically non-randomized and not powered to detect differences in meaningful clinical outcomes. However, it is reasonable to acknowledge the challenges associated with prehospital research in resuscitation of bleeding trauma patients, such as proper classification and enrollment of participants and proper randomization. Thus, blood product transfusion in the treatment of prehospital combat casualties and civilian trauma warrants continuing investigation in a variety of prehospital environments to generate robust evidence.89
Lastly, the safety and efficacy of TXA has been widely investigated in the perioperative environment and other clinical settings after the release of the Clinical Randomization of an Antifibrinolytic in Significant Hemorrhage (CRASH)-2 study.90 Overall, studies have demonstrated that TXA use is safe and is associated with both decreased requirements for allogeneic blood product transfusion and improvement of coagulation profiles.91 92 However, in prehospital environments, there is still room to improve evidence. The CRASH-3 study, a multicenter RCT conducted in patients with isolated TBI, assessed the use of TXA compared with placebo on hospital arrival.93 The study found no difference in TBI-related death, though identified increased efficacy with earlier treatment in those with mild to moderate TBI.93 Additionally, the risk of vascular occlusive events and seizures was similar between groups.93 A second study assessing patients with isolated brain injury given out-of-hospital TXA, the Resuscitation Outcomes Consortium (ROC) TXA trial, reported no difference in the neurofunctional outcome at 6 months after injury, in the 28-day mortality between groups, and in the progression of intracranial hemorrhage receiving TXA compared with the placebo group.94 Third, the recently published Study of Tranexamic Acid During Air Medical and Ground Prehospital Transport (STAAMP) trial, a further multicenter RCT conducted in prehospital trauma patients at risk of hemorrhage, reported no difference in 30-day mortality rates, 6 and 24-hour blood and blood component transfusion requirements, and in the incidence of pulmonary embolism or deep vein thrombosis in the group receiving prehospital TXA administration compared with placebo.95 However, in patients who received prehospital TXA administration within 1 hour of injury and in those with evidence of prehospital severe shock, post hoc subgroup analysis suggested that prehospital TXA is associated with lower 30-day mortality. Therefore, the CRASH-3 study, the ROC TXA trial, and the STAAMP trial have reported important differences and findings that warrant consideration and further investigation in studies with improved patient selection methods to further explore the efficacy of TXA in important clinical outcomes.
Strengths and limitations of this review
This is the first systematic review to appraise the TCCC literature and identify knowledge gaps on the management of trauma patients in civilian and military prehospital settings. In addition, the review highlights areas within these guidelines requiring further investigation. The primary limitation of this review is that most data identified are non-randomized, and therefore confounding is highly inevitable. As demonstrated through our findings, most advances relating to the MARCH components occur from registry-based quality improvement or observational cohort studies. Clinical and methodological heterogeneity between the study populations, interventions and measured outcomes introduces added difficulty in study comparability. However, research in trauma is challenging. Properly designed RCTs in prehospital settings are not always possible. In addition, funding for such studies is becoming increasingly difficult to obtain. Recent recommendations from the National Academies of Sciences, Engineering and Medicine are beginning to emphasize the utility of registry-based performance improvement as the optimal method of advancing care and outcomes in prehospital and military environments.96 In summary, though randomized evidence is lacking, it is equally important to acknowledge the complex reasons for which this deficit exists.