This study is the first that accurately quantifies a marked improvement in survival following major trauma on UK combat operations during the last decade. These findings provide unprecedented detail on the military casualties sustained by the UK Armed Services on combat operations. The results demonstrate that a majority of injuries from hostile action were primarily from blast and fragmentation trauma resulting from explosive devices, with the extremities being more likely than any other region to be injured.
This study echoes the finding of our US colleagues that support the belief that survival has improved over the conflict.14 However, previous attempts to quantify this improvement have relied on the case-fatality rate, that is, the ratio of fatalities to total casualties (killed and wounded). While we cite this figure in Table 1, the authors regard this methodology as vulnerable to multiple confounders, although it has the advantage of comparison with historical records, which is impossible with more sophisticated techniques such as NISS.
It is important to acknowledge that although obviously very important, mortality is a crude outcome measure. The UK JTTR is investigating the possibility of measuring subsequent disability, functional recovery, or patient-reported quality of life, but this has inherent challenges, and no major trauma registry has successfully incorporated this. There is limited evidence that casualties with severe injuries have returned to military service, and this can be regarded as a surrogate marker of functional recovery.15
The UK Military trauma system is not analogous to a civilian trauma network. Aside from the initial invasion of Iraq and special operations, the UK DMS did not deploy forward surgical teams and instead relied on rapid transit from point of wounding to a single field hospital in each operational theater. The distinction between prehospital and hospital care has become blurred with “hospital techniques,” that is, resuscitation with blood (from 2008), intubation, and thoracostomies being taken into the prehospital environment, with the overwhelming majority of UK casualty retrieval helicopters carrying a doctor capable of delivering these techniques with demonstrable improvements is survival.16
There is some distinction between the UK and US strategies in this regard. By virtue of the larger area of operations of US forces and resultant longer transit times, the US Military trauma system deploys forward surgical teams that perform initial damage-control procedures before transfer on to a field hospital.17,18 A further distinction is that US helicopters transferring casualties from point of wounding to a forward surgical team and onward to the field hospital are staffed by emergency medical technicians and paramedics rather than physicians.16 The UK also returns patients direct to a single treatment facility (the Royal Centre for Defence Medicine, Birmingham, United Kingdom), whereas the US returns patients to three main US-based hospitals after transit via the Landstuhl Regional Medical Center (Rhineland-Palatinate, Germany).
The structured MACE approach to improving combat casualty care is similar between the UK and US military medical services. Both operate a JTTR that are sufficiently aligned to allow coordinated joint research.16,19–21
The finding of this study that 70% of injuries resulting from hostile action are from explosive weapons is entirely consistent with the experience from the previous half century of conflict. In modern warfare, the majority of injuries have similarly resulted from explosive weapons, that is, landmines, rockets, grenades, improvised explosive devices, and mortars as demonstrated in Table 3. Our findings that the extremities are the most likely body region to be injured are consistent with the published literature from recent conflicts. Interestingly however, extremity injuries form a relatively smaller proportion of all injuries in this study (Table 3) compared with previous studies.
The management of polytrauma is complex, and when casualties are injured on an overseas battlefield, this complexity is increased significantly. In an already complex system of care, pinpointing specific factors responsible for improved odds of survival is challenging. From the presented results, it is not possible to conclude which specific intervention and system changes improved outcomes. We propose that the improvement in survival demonstrated in this study is likely caused by the aggregation of multiple summative improvements in techniques across a system that adopts an “end-to-end” approach, blurring the boundaries between point of wounding treatment, prehospital en route care, receiving field hospital management, and in-flight care during repatriation to continuing care in the National Health Service.
If such results are to be achieved in the already fast improving civilian trauma sector, no single or limited number of advances are necessarily required or indeed expected in the near future; rather, smaller cumulative improvements across the care pathway could yield significant benefit in trauma outcomes.
Management of trauma in deployed UK Military medical facilities is both consultant led and consultant delivered. With the high tempo and unpredictability of military operations during the last decade, consultants have gained experience across multiple previous deployments. This knowledge is further consolidated by the cyclical predeployment training system through which clinicians returning from deployment instruct their colleagues about to deploy via the bespoke Military Operational Surgical Training (MOST) course run with the assistance of the Royal College of Surgeons of England since 2007. This team-based training involves rehearsing damage-control resuscitation and surgical techniques on cadaveric material and third-generation simulation mannequins with the complete team of surgeons, anesthetists, emergency physicians, and theater staff using current equipment and protocols. It is possible that improvements in UK Military trauma system performance achieved during the last 10 years might be lost at the cessation of hostilities. The associated decreased exposure to severe combat trauma may result in a loss of some of the gains in survival demonstrated by this study in the initial phases of subsequent conflicts.
There has been a significant improvement in the understanding of resuscitation with blood products during the last 10 years. The traditional concept of restoring a casualty’s hemoglobin concentration by administering packed red blood cells has been augmented by the administration of packed red blood cells and fresh frozen plasma at approximately a 1:1 ratio with early platelet administration.27 This strategy was improved in the second half of the study period by massive transfusions being guided by real-time, near-patient thrombelastography (introduced from 2009), which has supplanted traditional measures of “clotting,” allowing a tailored correction of coagulopathy as part of the resuscitation phase.28 Large volumes of blood products that are often required in catastrophic exsanguinating hemorrhage are infused through high-volume blood warmers at rates of up to 1 L/min. In addition, the use of tranexamic acid has been shown to improve survival following major trauma in both civilian and military studies and is now routinely administered at the prehospital setting within the military trauma system.19,29 These improvements in care were directly resulting from the systematic MACE system of analyzing practice and outcomes and rapidly altering doctrine and training accordingly as well as the ability to increase the numbers available for analyses by pooling UK and US JTTR data.16,19
Two or more anesthetists manage the casualty’s airway, ventilation, anesthetic, and resuscitation. An operating department practitioner and a transfusion technician aid them. Adapting these structures to the civilian setting will require recognition that a team of doctors and technicians, rather than a single doctor, is required for the anesthetic/resuscitation of the severely injured patient in the way described.30
Helicopters have been routinely used by the military to transport casualties from near point of wounding to surgical facilities since the US-Vietnam conflict.31 During the conflicts of the last decade, the UK Military developed a consultant-led retrieval service that permits prehospital advanced interventions. This service has been shown to improve outcomes when compared with non–physician-led conventional helicopter casualty retrieval in a selected group of patients with Injury Severity Scores (ISSs) between 16 and 50.16
Personal protective equipment improved during the study period and now offers protection to the head, eyes, and torso as standard with personnel able to increase protection of the neck, shoulders, thorax, groin, and thighs, depending on perceived threat.
We would like to acknowledge the inherent weaknesses of this study. First, although our results quantify improved survival, an observational study of this type is clearly unable to identify specific treatment or intervention responsible for this effect. Second, data modeling is inherently imperfect. The high shrinkage estimate of Model 2 implies that it does not demonstrate significant overfitting; therefore, we are confident that the model estimates are reliable.
Third, we acknowledge that NISS is an anatomic measure only and might underestimate survival in a young and physically robust military population. Both the UK and US JTTR collect Trauma and Injury Severity Scores (TRISS), which also incorporates physiologic variables; however, these calculations are both based on coefficients for either blunt or penetrating injury developed in the 1980s. There is currently no coefficient for explosive injury, and given that this is the most common injury mechanism in the registry, we regard this as a significant limitation with the use of TRISS in this population.
The output from Model 2 in which NISS is incorporated as a continuous variable is summarized in Supplemental Digital Content 5 (http://links.lww.com/TA/A534). For this model, the likelihood ratio test comparing the specified model against the null model returned p values of less than 0.0001. The le Cessie–Van Houwelingen–Copas–Hosmer goodness-of-fit test statistics for Model 2 gives a p value of 0.314. In addition, this model exhibits high discriminatory power with a C statistic of 0.982 and a shrinkage estimate of 0.9944.
This study shows a dramatic improvement in survival over the 10 years, caring for UK casualties across the conflicts in Iraq and Afghanistan. These results suggest that future military trauma system performance metrics will need reconsideration to be sensitive to change from the current performance level. More sophisticated outcome measures the performance of combat casualty care systems including morbidity and functional recovery are required to drive future improvement.
J.P-B. conceived of this study; J.P-B, S.A.G.R. and M.J.M. contributed to the study design. J.R.B.B. contributed to data analyses and graph preparation. J.P-B., S.A.G.R., and M.J.M. prepared the manuscript.
We acknowledge the hard work, dedication, and professionalism of all the members of the Defence Medical Services and the National Health Service that cared for the casualties described in this work. We also thank the Clinical Information and Exploitation Team, Joint Medical Command, and UK Defence Statistics (Health) for collecting, collating, and identifying appropriate data for this article. We also thank Brig. Tim Hodgetts L/RAMC for his role in leading the development of the Joint Theatre Trauma Register and Major Trauma Audit for Clinical Effectiveness (MACE) process.
J.P.B., S.A.R. and M.J.M. are serving officers in the Royal Navy. All authors have completed the ICMJE uniform disclosure form and declare no support from any organization for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years; and no other relationships or activities that could seem to have influenced the submitted work.
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Combat injuries; survival; war; injury severity
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