Analysis of 828 servicemen killed or injured by explosion in Northern Ireland 1970-84: the Hostile Action Casualty System

Esophageal pressure monitoring and its clinical significance in severe blast lung injury

Background

The incidence of blast lung injury (BLI) has been escalating annually due to military conflicts and industrial accidents. Currently, research into these injuries predominantly uses animal models. Despite the availability of various models, there remains a scarcity of studies focused on monitoring respiratory mechanics post-BLI. Consequently, our objective was to develop a model for monitoring esophageal pressure (Pes) following BLI using a biological shock tube (BST), aimed at providing immediate and precise monitoring of respiratory mechanics parameters post-injury.

Methods

Six pigs were subjected to BLI using a BST, during which Pes was monitored. We assessed vital signs; conducted blood gas analysis, hemodynamics evaluations, and lung ultrasound; and measured respiratory mechanics before and after the inflicted injury. Furthermore, the gross anatomy of the lungs 3 h post-injury was examined, and hematoxylin and eosin staining was conducted on the injured lung tissues for further analysis.

Results

The pressure in the experimental section of the BST reached 402.52 ± 17.95 KPa, with a peak pressure duration of 53.22 ± 1.69 ms. All six pigs exhibited an anatomical lung injury score ≥3, and pathology revealed classic signs of severe BLI. Post-injury vital signs showed an increase in HR and SI, along with a decrease in MAP (p < 0.05). Blood gas analyses indicated elevated levels of Lac, CO2-GAP, A-aDO2, HB, and HCT and reduced levels of DO2, OI, SaO2, and OER (p < 0.05). Hemodynamics and lung ultrasonography findings showed increased ELWI, PVPI, SVRI, and lung ultrasonography scores and decreased CI, SVI, GEDI, and ITBI (p < 0.05). Analysis of respiratory mechanics revealed increased Ppeak, Pplat, Driving P, MAP, PEF, Ri, lung elastance, MP, Ptp, Ppeak - Pplat, and ΔPes, while Cdyn, Cstat, and time constant were reduced (p < 0.05).

Conclusion

We have successfully developed a novel respiratory mechanics monitoring model for severe BLI. This model is reliable, repeatable, stable, effective, and user-friendly. Pes monitoring offers a non-invasive and straightforward alternative to blood gas analysis, facilitating early clinical decision-making. Our animal study lays the groundwork for the early diagnosis and management of severe BLI in clinical settings.

Effectiveness of Body Armor Against Shock Waves: Preventing Blast Injury in a Confined Space

Introduction Blast injuries in modern society often occur owing to terrorist attacks in confined spaces, particularly in urban settings, indoors, and in vehicles, leading to significant damage. Therefore, it is important to focus on blast injuries in confined spaces rather than in conventional open-field experiments. Materials and methods We used an air-driven shock wave generator (blast tube) established indoors in 2017 and conducted basic research to potentially save the lives of patients with blast injuries. Under general anesthesia, pigs were divided into with body armor (BA) and without BA groups. The pigs were fixed in the measurement chamber with their dorsal chest directly exposed to the shock wave. The driving pressure was set at 3.0 MPa to achieve a mortality rate of approximately 50%. A generated shock wave was directly applied to the pigs. Comparisons were made between the groups with respect to cardiac arrest and survival, as well as apnea, bradycardia, and hypotension, which are the triad of blast lung. Autopsies were performed to confirm the extent of the organ damage. Statistical analysis was performed using Fisher's exact test, and statistical significance was set at p<0.05. The animal experimentation was conducted according to the protocol reviewed and approved by the Animal Ethics Committee of the National Defense Medical College Hospital (approval number 19041). Results Eight pigs were assigned to the BA group and seven pigs to the non-BA group. In the non-BA group, apnea was observed in four of seven cases, three of which resulted in death. None of the eight pigs in the BA group had respiratory arrest; notably, all survived. Hypotension was observed in some pigs in each group; however, there were no cases of bradycardia in either group. Statistical analysis showed that wearing BA significantly reduced the occurrence of respiratory and cardiac arrest (p=0.026) but not survival (p=0.077). No significant differences were found in other vital signs. Conclusions Wearing BA with adequate neck and chest protection reduced mortality and it was effective to reduce cardiac and respiratory arrest against shock wave exposure. Mortality from shock wave injury appears to be associated with respiratory arrest, and the avoidance of respiratory arrest may lead to survival.

Observations from the Korean War for Modern Military Medicine

This paper reviews developments in military medicine during the Korean War and places them in the evolution of military medical lessons from the Second World War and the subsequent development of military medicine through the Vietnam War to the present day. The analysis is structured according to the '10 Instruments of Military Healthcare.' Whilst there were incremental developments in military medicine in all these areas, several innovations are specifically attributed to the Korean War. The introduction of helicopters to the battlefield led to the establishment of dedicated medical evacuation helicopters crewed with medical personnel and the evolution into the DUSTOFF system during the Vietnam War. Helicopter evacuation was the primary medical evacuation system in the wars in Iraq and Afghanistan. The establishment of the Mobile Army Surgical Hospital during the Korean War were founded upon the US Auxiliary Surgical Groups or the UK Casualty Clearing Stations of World War II. The requirement for resuscitation and surgical teams close to the battlefield has endured through the development of mobile hospitals of varying sizes from Field Surgical Teams to the current 'modular' Hospital Centre and other international equivalents. There were many innovations in the clinical care of battle casualties covering wound shock, surgical techniques, preventive medicine, and acute psychiatric care that refreshed or advanced knowledge from the Second World War. These were enabled through the establishment of medical research programs that were managed within the theatre of operations. Further advances in all these clinical topics can be observed through the Vietnam War to the wars in Iraq and Afghanistan - all of which were underpinned by institutional directed research programs. Finally, collaboration between international military medical services and the development of Korean military medical services is a major theme of this review. This 'military-tomilitary' and 'civil-military' medical engagement was also a major activity during the Vietnam War and more recently in Iraq and Afghanistan. Overall, the topics and themes in military medicine that were important during the Korean War can be considered to be part of trajectory of innovation in military medicine have been replicated in many subsequent wars. The paper also highlights some 'lessons' from World War II that had to be relearned in the Korean War, and some observations from the Korean War that had to be relearned in subsequent wars.

A Distinct Metabolite Signature in Military Personnel Exposed to Repetitive Low-Level Blasts

Military Breachers and Range Staff (MBRS) are subjected to repeated sub-concussive blasts, and they often report symptoms that are consistent with a mild traumatic brain injury (mTBI). Biomarkers of blast injury would potentially aid blast injury diagnosis, surveillance and avoidance. Our objective was to identify plasma metabolite biomarkers in military personnel that were exposed to repeated low-level or sub-concussive blast overpressure. A total of 37 military members were enrolled (18 MBRS and 19 controls), with MBRS having participated in 8–20 breaching courses per year, with a maximum exposure of 6 blasts per day. The two cohorts were similar except that the number of blast exposures were significantly higher in the MBRS, and the MBRS cohort suffered significantly more post-concussive symptoms and poorer health on assessment. Metabolomics profiling demonstrated significant differences between groups with 74% MBRS classification accuracy (CA). Feature reduction identified 6 metabolites that resulted in a MBRS CA of 98%, and included acetic acid (23.7%), formate (22.6%), creatine (14.8%), acetone (14.2%), methanol (12,7%), and glutamic acid (12.0%). All 6 metabolites were examined with individual receiver operating characteristic (ROC) curve analyses and demonstrated areas-under-the-curve (AUCs) of 0.82–0.91 (P ≤ 0.001) for MBRS status. Several parsimonious combinations of three metabolites increased accuracy of ROC curve analyses to AUCs of 1.00 (P < 0.001), while a combination of volatile organic compounds (VOCs; acetic acid, acetone and methanol) yielded an AUC of 0.98 (P < 0.001). Candidate biomarkers for chronic blast exposure were identified, and if validated in a larger cohort, may aid surveillance and care of military personnel. Future point-of-care screening could be developed that measures VOCs from breath, with definitive diagnoses confirmed with plasma metabolomics profiling.

Guidelines to inform the generation of clinically relevant and realistic blast loading conditions for primary blast injury research

'Primary' blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. With continued experimental focus on PBI mechanisms, recently on blast traumatic brain injury, meaningful test outcomes rely on appropriate simulated conditions. Selected PBI predictive criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) are combined and plotted to provide rationale for generating clinically relevant loading conditions. Using blast engineering theory, explosion characteristics including blast wave parameters and fireball dimensions were calculated for a range of charge masses assuming hemispherical surface detonations and compared with PBI criteria. While many experimental loading conditions are achievable, this analysis demonstrated limits that should be observed to ensure loading is clinically relevant, realistic and practical. For PBI outcomes sensitive only to blast overpressure, blast scaled distance was demonstrated to be a useful parameter for guiding experimental design as it permits flexibility for different experimental set-ups. This analysis revealed that blast waves should correspond to blast scaled distances of 1.75<Z<6.0 to generate loading conditions found outside the fireball and of clinical relevance to a range of PBIs. Blast waves with positive phase durations (2-10 ms) are more practical to achieve through experimental approaches, while representing realistic threats such as improvised explosive devices (ie, 1-50 kg trinitrotoluene equivalent). These guidelines can be used by researchers to inform the design of appropriate blast loading conditions in PBI experimental investigations.

The Injury Mechanism of Traumatic Amputation

Traumatic amputation has been one of the most defining injuries associated with explosive devices. An understanding of the mechanism of injury is essential in order to reduce its incidence and devastating consequences to the individual and their support network. In this study, traumatic amputation is reproduced using high-velocity environmental debris in an animal cadaveric model. The study findings are combined with previous work to describe fully the mechanism of injury as follows. The shock wave impacts with the casualty, followed by energised projectiles (environmental debris or fragmentation) carried by the blast. These cause skin and soft tissue injury, followed by skeletal trauma which compounds to produce segmental and multifragmental fractures. A critical injury point is reached, whereby the underlying integrity of both skeletal and soft tissues of the limb has been compromised. The blast wind that follows these energised projectiles completes the amputation at the level of the disruption, and traumatic amputation occurs. These findings produce a shift in the understanding of traumatic amputation due to blast from a mechanism predominately thought mediated by primary and tertiary blast, to now include secondary blast mechanisms, and inform change for mitigative strategies.

Primary Blast Lung Injury: The UK Military Experience

INTRODUCTION

Primary blast lung injury occurs when an explosive shock wave passes through the thorax and transits through tissues of varying densities. It requires close proximity to an explosion and presents quick with respiratory distress in survivors.

MATERIALS AND METHODS

The Joint Theatre Trauma Registry and the Defence Statistics (Health) Database were interrogated for casualties injured as a result of an explosion during the conflict in Afghanistan. The case notes and imaging of casualties meeting the criteria for diagnosis were reviewed. Demographic and clinical data on casualties with primary blast lung injury were analyzed.

RESULTS

848 blast-exposed casualties survived to discharge from intensive care, and 238 blast-exposed casualties were killed in action. Following exclusions, 111 case notes and all postmortem reports were reviewed in detail. About, 25 casualties had isolated primary blast lung injury (2.9% of casualties surviving to discharge from intensive care) and 31 nonsurvivors (13% of nonsurvivors) had the disease documented at postmortem. Severe cases of primary blast lung injury required an estimated average of 4.5 days of conventional mechanical ventilation.

CONCLUSIONS

8.1% of blast exposed casualties suffered primary blast lung injury. It was a less severe disease than other nontraumatic forms of acute lung injury and did not cause deaths once a casualty had reached a combat support hospital. It was well managed with a relatively brief period of conventional mechanical ventilation.

Pelvic Protection Limiting Lower Limb Flail Reduces Mortality

Pelvic blast injury is one of the most severe patterns of injury to be sustained by casualties of explosions. We have previously identified the mechanism of injury in a shock tube-mediated murine model, linking outward flail of the lower limbs to unstable pelvic fractures and vascular injury. As current military pelvic protection does not protect against lower limb flail, in this study we have utilized the same murine model to investigate the potential of novel pelvic protection to reduce injury severity. Fifty cadaveric mice underwent shock-tube blast testing and subsequent injury analysis. Pelvic protection limiting lower limb flail resulted in a reduction of pelvic fracture incidence from both front-on (relative risk (RR) 0.5, 95% confidence intervals (CIs) 0.3-0.9, p < 0.01) and under-body (RR 0.3, 95% CI 0.1-0.8 p < 0.01) blast, with elimination of vascular injury in both groups (p < 0.001). In contrast, pelvic protection, which did not limit flail, had no effect on fracture incidence compared to the control group and was only associated with a minimal reduction in vascular injury (RR 0.6, 95% CI 0.4-1.0, p < 0.05). This study has utilized a novel strategy to provide proof of concept for the use of pelvic protection, which limits limb flail to mitigate the effects of pelvic blast injury.

Important learning points arising from the focused issue dedicated to the Terror and Disaster Surgical Care (TDSC®) course on mass casualty incident management

The Terror and Disaster Surgical Care (TDSC®) course on mass casualty incident management was formulated in Germany by military medical personnel, who have been deployed to conflict areas, but also work in hospitals open for the lay public. In this manuscript we discuss different concepts and ideas taught in this course as these are described in a focused issue recently published in the European Journal of Trauma and Emergency Surgery. We provide reinforcement for some of the ideas conveyed. We provide alternative views for others. Injuries following explosions are different from blunt and penetrating trauma and at times demand a different approach. There are probably several ways to manage a mass casualty incident depending on the setup of the organization. An open discussion on the topics presented in the manuscripts included in the focused issue on military and disaster surgery should enrich everyone.

Fibrinogen γ-Chain Peptide-Coated Adenosine 5' Diphosphate-Encapsulated Liposomes Rescue Mice From Lethal Blast Lung Injury via Adenosine Signaling

OBJECTIVES

Fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes can accumulate via dodecapeptide HHLGGAKQAGDV interactions at bleeding sites where they release adenosine 5'-diphosphate that is rapidly metabolized to adenosine, which has tissue-protective effects. We investigated the efficacy of fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes to treat blast lung injury, with a focus on adenosine signaling.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adult male C57BL/6 mice.

INTERVENTIONS

Mice were pretreated with fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes, dodecapeptide HHLGGAKQAGDV-(phosphate-buffered saline)-liposomes, adenosine 5' diphosphateliposomes, or phosphate-buffered saline-liposomes. Five minutes after treatment the mice received a single laser-induced shock wave (1.8 J/cm) that caused lethal blast lung injury, and their survival times and lung injuries were then assessed. We also evaluated the therapeutic effect of posttreatment with fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes or H12-(phosphate-buffered saline)-liposomes 1 minute after laser-induced shock wave exposure. To examine the effect of adenosine signaling, adenosine A2A receptor (ZM241385) or adenosine A2B receptor (PSB 1115) antagonists were administered to the mice 1 hour before the pretreatment with fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes that was followed by laser-induced shock wave exposure.

MEASUREMENTS AND MAIN RESULTS

Pre- and posttreatment with fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes significantly increased mouse survival [fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes: 58% survival vs H12-(phosphate-buffered saline)-liposomes: 8%; p < 0.05 (posttreatment)] and mitigated pulmonary tissue damage/hemorrhage and neutrophil accumulation after laser-induced shock wave exposure. fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes accumulated at pulmonary vessel injury sites after laser-induced shock wave exposure with both pre- and posttreatment. Furthermore, pretreatment with fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes reduced albumin and macrophage inflammatory protein-2 levels in bronchoalveolar lavage fluid. Although fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV)-coated adenosine 5'-diphosphate-encapsulated liposomes pretreatment did not affect blood coagulation activity in the injured mice, its beneficial effect on blast lung injury was significantly abrogated by A2A or A2B adenosine receptor antagonists (A2A antagonist: 17% survival; A2B antagonist: 33% vs dimethyl sulfoxide control: 80%; p < 0.05, respectively).

CONCLUSIONS

Fibrinogen γ-chain (dodecapeptide HHLGGAKQA GDV)-coated adenosine 5'-diphosphate-encapsulated liposomes may be effective against blast lung injury by promoting tissue-protective adenosine signaling and could represent a novel controlled-release drug delivery system.

Blast Injuries: From Improvised Explosive Device Blasts to the Boston Marathon Bombing

Although most trauma centers have experience with the imaging and management of gunshot wounds, in most regions blast wounds such as the ones encountered in terrorist attacks with the use of improvised explosive devices (IEDs) are infrequently encountered outside the battlefield. As global terrorism becomes a greater concern, it is important that radiologists, particularly those working in urban trauma centers, be aware of the mechanisms of injury and the spectrum of primary, secondary, tertiary, and quaternary blast injury patterns. Primary blast injuries are caused by barotrauma from the initial increased pressure of the explosive detonation and the rarefaction of the atmosphere immediately afterward. Secondary blast injuries are caused by debris carried by the blast wind and most often result in penetrating trauma from small shrapnel. Tertiary blast injuries are caused by the physical displacement of the victim and the wide variety of blunt or penetrating trauma sustained as a result of the patient impacting immovable objects such as surrounding cars, walls, or fences. Quaternary blast injuries include all other injuries, such as burns, crush injuries, and inhalational injuries. Radiography is considered the initial imaging modality for assessment of shrapnel and fractures. Computed tomography is the optimal test to assess penetrating chest, abdominal, and head trauma. The mechanism of blast injuries and the imaging experience of the victims of the Boston Marathon bombing are detailed, as well as musculoskeletal, neurologic, gastrointestinal, and pulmonary injury patterns from blast injuries.

Blast Trauma: The Fourth Weapon of Mass Destruction

Injury from blast is becoming more common in the non-military population. This is primarily a result of an increase in politically motivated bombings within the civilian sector. Explosions unrelated to terrorism may also occur in the industrial setting. Civilian physicians and surgeons need to have an understanding of the pathomechanics and physiology of blast injury and to recognize the hallmarks of severity in order to increase survivorship. Because victims may be transported rapidly to the hospital, occult injury to gas and fluid containing organs (particularly the ears, bowel and lungs) may go unrecognized. Information surrounding the physical environment of the explosion (whether inside or outside, underwater, associated building collapse, etc) will prove useful. Most of the immediate deaths are caused by primary blast injury from the primary blast wave, but secondary blast injury from flying debris can also be lethal and involve a much wider radius. Liberal use of X-ray examination in areas of skin punctures will help to identify a need for exploration and/or foreign body removal. Biologic serum markers may have a role in identifying victims of primary blast injury and assist in monitoring their clinical progress. Tertiary blast injury results from the airborne propulsion of the victim by the shockwave and is a source of additional blunt head and torso trauma as well as fractures. Miscellaneous (quaternary) blast injury include thermal or dust inhalation exposure as well as crush and compartment syndromes from building collapse. Any explosion has the potential to be associated with nuclear, biologic or chemical contaminants, and this should remain a consideration for healthcare givers until proven otherwise.

Traumatic amputations

Traumatic amputations remain one of the most emotionally disturbing wounds of conflict, as demonstrated by their frequent use in films to illustrate the horrors of war. Unfortunately, they remain common injuries, particularly following explosions, and, in addition, many survivors require primary amputation for unsalvageable injuries or to save their life. A third group, late amputations, is being increasingly recognised, often as a result of the sequelae of complex foot injuries. This article will look at the epidemiology of these injuries and their acute management, complications and outcome.

The initial response to the Boston marathon bombing: lessons learned to prepare for the next disaster

OBJECTIVE

We discuss the strengths of the medical response to the Boston Marathon bombings that led to the excellent outcomes. Potential shortcomings were recognized, and lessons learned will provide a foundation for further improvements applicable to all institutions.

BACKGROUND

Multiple casualty incidents from natural or man-made incidents remain a constant global threat. Adequate preparation and the appropriate alignment of resources with immediate needs remain the key to optimal outcomes.

METHODS

A collaborative effort among Boston's trauma centers (2 level I adult, 3 combined level I adult/pediatric, 1 freestanding level I pediatric) examined the details and outcomes of the initial response. Each center entered its respective data into a central database (REDCap), and the data were analyzed to determine various prehospital and early in-hospital clinical and logistical parameters that collectively define the citywide medical response to the terrorist attack.

RESULTS

A total of 281 people were injured, and 127 patients received care at the participating trauma centers on that day. There were 3 (1%) immediate fatalities at the scene and no in-hospital mortality. A majority of the patients admitted (66.6%) suffered lower extremity soft tissue and bony injuries, and 31 had evidence for exsanguinating hemorrhage, with field tourniquets in place in 26 patients. Of the 75 patients admitted, 54 underwent urgent surgical intervention and 12 (22%) underwent amputation of a lower extremity.

CONCLUSIONS

Adequate preparation, rapid logistical response, short transport times, immediate access to operating rooms, methodical multidisciplinary care delivery, and good fortune contributed to excellent outcomes.

[Primary treatment of penetrating injuries. Part 1: blast trauma]

Blast injuries may result from a variety of causes but the biomechanical impact and pathophysiological consequences do not differ between domestic or industrial accidents or even terrorist attacks. However, this differentiation relevantly affects the tactical procedures of the rescue teams. Focusing on further detonations, top priority is given to the personal safety of all rescue workers. The rareness of blast injuries in a civilian setting results in a lack of experience on the one hand but on the other hand the complexity of blast injuries to the human body places high demands on the knowledge and skills of the entire rescue team for competent treatment. The purpose of this article is to explain the physicochemical principles of explosions and to convey tactical and medical knowledge to emergency medical services.

Combat Casualty Care research programme

The Combat Casualty Care research programme is an integrated suite of projects designed to address Defence Medical Services' research needs for casualty care. The programme covers a broad spectrum of topics ranging from the pathophysiological and immunological impact of military relevant injuries to the effects of these disturbances on the response to early treatment. Dstl Porton Down has a long history of studying military injuries and has developed models, both in vivo and physical, to address the research needs. The work is conducted in close collaboration with clinical colleagues at the Royal Centre for Defence Medicine who have direct experience of the clinical issues faced by combat casualties and insights into the potential clinical implications of emerging strategies. This article reviews progress in research areas spanning forward resuscitation, with a particular focus on blast-related injuries, trauma coagulopathy, effects of drugs on the response to haemorrhage and deployed research. A significant 'value added' component has been the underpinning of higher degrees for seconded military clinicians at Dstl Porton Down who have made a valuable contribution to the overall programme.

Disaster preparedness, pediatric considerations in primary blast injury, chemical, and biological terrorism

Both domestic and foreign terror incidents are an unfortunate outgrowth of our modern times from the Oklahoma City bombings, Sarin gas attacks in Japan, the Madrid train bombing, anthrax spores in the mail, to the World Trade Center on September 11(th), 2001. The modalities used to perpetrate these terrorist acts range from conventional weapons to high explosives, chemical weapons, and biological weapons all of which have been used in the recent past. While these weapons platforms can cause significant injury requiring critical care the mechanism of injury, pathophysiology and treatment of these injuries are unfamiliar to many critical care providers. Additionally the pediatric population is particularly vulnerable to these types of attacks. In the event of a mass casualty incident both adult and pediatric critical care practitioners will likely be called upon to care for children and adults alike. We will review the presentation, pathophysiology, and treatment of victims of blast injury, chemical weapons, and biological weapons. The focus will be on those injuries not commonly encountered in critical care practice, primary blast injuries, category A pathogens likely to be used in terrorist incidents, and chemical weapons including nerve agents, vesicants, pulmonary agents, cyanide, and riot control agents with special attention paid to pediatric specific considerations.

Primary blast lung injury prevalence and fatal injuries from explosions: insights from postmortem computed tomographic analysis of 121 improvised explosive device fatalities

BACKGROUND

Primary blast lung injury (PBLI) is an acknowledged cause of death in explosive blast casualties. In contrast to vehicle occupants following an in-vehicle explosion, the injury profile, including PBLI incidence, for mounted personnel following an external explosion has yet to be as well defined.

METHODS

This retrospective study identified 146 cases of UK military personnel killed by improvised explosive devices (IEDs) between November 2007 and July 2010. With the permission of Her Majesty's Coroners, relevant postmortem computed tomography imaging was analyzed. PBLI was diagnosed by postmortem computed tomography. Injury, demographic, and relevant incident data were collected via the UK Joint Theatre Trauma Registry.

RESULTS

Autopsy results were not available for 1 of 146 cases. Of the remaining 145 IED fatalities, 24 had catastrophic injuries (disruptions), making further study impossible, leaving 121 cases; 79 were dismounted (DM), and 42 were mounted (M). PBLI was noted in 58 cases, 33 (79%) of 42 M fatalities and 25 (32%) of 79 DM fatalities (p < 0.0001). Rates of associated thoracic trauma were also significantly greater in the M group (p < 0.006 for all). Fatal head (53% vs. 23%) and thoracic trauma (23% vs. 8%) were both more common in the M group, while fatal lower extremity trauma (7% vs. 48%) was more commonly seen in DM casualties (p < 0.0001 for all).

CONCLUSION

Following IED strikes, mounted fatalities are primarily caused by head and chest injuries. Lower extremity trauma is the leading cause of death in dismounted fatalities. Mounted fatalities have a high incidence of PBLI, suggesting significant exposure to primary blast. This has not been reported previously. Further work is required to determine the incidence and clinical significance of this severe lung injury in explosive blast survivors. In addition, specific characteristics of the vehicles should be considered.

What the Intensive Care Doctor Needs to Know about Blast-Related Lung Injury

Explosions are currently the primary cause of military combat injuries. A minority of civilian trauma is also caused by explosions. People hurt by explosion are likely to present with complex injuries. The aim of the article is to explain the mechanism underlying these injuries and the associated physiology to help the intensive care clinician manage these casualties properly. The generic term ‘blast injury’ is applied to a collection of injuries caused by explosion. Components of blast injuries have precise definitions relating to the elements of the explosion that caused the injuries: primary blast injury is due to a shock wave, secondary blast injury is caused by fragments and debris colliding with the victim and tertiary blast injury is due to the casualty being thrown against solid objects. Primary blast injury results in damage principally in gas-containing organs, eg the lungs (blast lung) and can lead to impaired pulmonary gas transfer and hypoxaemia. Secondary blast injuries are often penetrating and can lead to haemorrhage while tertiary blast injuries are often blunt and involve substantial tissue damage. Survivors of explosions in confined spaces are more likely to exhibit primary blast injury than those injured in open spaces. The current military approach to immediate management is to apply the C ABC principle (arrest catastrophic haemorrhage first and then deal with airway, breathing and circulation) to achieve Damage Control Resuscitation. Early administration of blood products (plasma as well as red cells) is advocated for those suffering significant haemorrhage. Initial resuscitation is hypotensive to minimise risk of dislodging nascent clots. However, if evacuation is protracted (longer than one hour) then consideration should be given to improving blood flow / oxygen delivery by adopting a revised normotensive blood pressure target to reverse the deleterious consequences of the hypotensive shock state. Animal studies have shown that titrating FiO2 to a target SaO2 of 95% can improve survival and ‘buy time’ during hypotensive resuscitation. Ventilator strategies should use a lung-protective approach with permissive hypercapnia if necessary. Blast casualties are often a challenging group of patients needing expert, tailored, care. Outcome can be good especially in young, otherwise fit, casualties with more than 96% surviving to ICU discharge, although this figure may be lower with a mixed civilian group.

Identifying future 'unexpected' survivors: a retrospective cohort study of fatal injury patterns in victims of improvised explosive devices

OBJECTIVES

To identify potentially fatal injury patterns in explosive blast fatalities in order to focus research and mitigation strategies, to further improve survival rates from blast trauma.

DESIGN

Retrospective cohort study.

PARTICIPANTS

UK military personnel killed by improvised explosive device (IED) blasts in Afghanistan, November 2007-August 2010.

SETTING

UK military deployment, through NATO, in support of the International Security Assistance Force (ISAF) mission in Afghanistan.

DATA SOURCES

UK military postmortem CT records, UK Joint Theatre Trauma Registry and associated incident data.

MAIN OUTCOME MEASURES

Potentially fatal injuries attributable to IEDs.

RESULTS

We identified 121 cases, 42 mounted (in-vehicle) and 79 dismounted (on foot), at a point of wounding. There were 354 potentially fatal injuries in total. Leading causes of death were traumatic brain injury (50%, 62/124 fatal injuries), followed by intracavity haemorrhage (20.2%, 25/124) in the mounted group, and extremity haemorrhage (42.6%, 98/230 fatal injuries), junctional haemorrhage (22.2%, 51/230 fatal injuries) and traumatic brain injury (18.7%, 43/230 fatal injuries) in the dismounted group.

CONCLUSIONS

Head trauma severity in both mounted and dismounted IED fatalities indicated prevention and mitigation as the most effective strategies to decrease resultant mortality. Two-thirds of dismounted fatalities had haemorrhage implicated as a cause of death that may have been anatomically amenable to prehospital intervention. One-fifth of the mounted fatalities had haemorrhagic trauma which currently could only be addressed surgically. Maintaining the drive to improve all haemostatic techniques for blast casualties, from point of wounding to definitive surgical proximal vascular control, alongside the development and application of novel haemostatic interventions could yield a significant survival benefit. Prospective studies in this field are indicated.

Rat injury model under controlled field-relevant primary blast conditions: acute response to a wide range of peak overpressures

We evaluated the acute (up to 24 h) pathophysiological response to primary blast using a rat model and helium driven shock tube. The shock tube generates animal loadings with controlled pure primary blast parameters over a wide range and field-relevant conditions. We studied the biomechanical loading with a set of pressure gauges mounted on the surface of the nose, in the cranial space, and in the thoracic cavity of cadaver rats. Anesthetized rats were exposed to a single blast at precisely controlled five peak overpressures over a wide range (130, 190, 230, 250, and 290 kPa). We observed 0% mortality rates in 130 and 230 kPa groups, and 30%, 24%, and 100% mortality rates in 190, 250, and 290 kPa groups, respectively. The body weight loss was statistically significant in 190 and 250 kPa groups 24 h after exposure. The data analysis showed the magnitude of peak-to-peak amplitude of intracranial pressure (ICP) fluctuations correlates well with mortality rates. The ICP oscillations recorded for 190, 250, and 290 kPa are characterized by higher frequency (10-20 kHz) than in other two groups (7-8 kHz). We noted acute bradycardia and lung hemorrhage in all groups of rats subjected to the blast. We established the onset of both corresponds to 110 kPa peak overpressure. The immunostaining against immunoglobulin G (IgG) of brain sections of rats sacrificed 24-h post-exposure indicated the diffuse blood-brain barrier breakdown in the brain parenchyma. At high blast intensities (peak overpressure of 190 kPa or more), the IgG uptake by neurons was evident, but there was no evidence of neurodegeneration after 24 h post-exposure, as indicated by cupric silver staining. We observed that the acute response as well as mortality is a non-linear function over the peak overpressure and impulse ranges explored in this work.

Serum neutrophil gelatinase-associated lipocalin in ballistic injuries: a comparison between blast injuries and gunshot wounds

Neutrophil gelatinase-associated lipocalin (NGAL) is part of a functionally diverse family of proteins that generally bind small, hydrophobic ligands. Neutrophil gelatinase-associated lipocalin is expressed in a number of human tissues including gastrointestinal, respiratory, and urinary tracts and tends to rise in response to inflammation. For this reason, we hypothesized that levels of NGAL might be expressed at higher levels after blast injury compared with other ballistic injury.

PURPOSE

The purpose of this study is to test the hypothesis that NGAL may be a marker of injury severity in blast injury.

MATERIALS

Twenty-three combat casualties (13 blast, 10 gunshot wounds) admitted to the multinational role 3 facility in Helmand province were studied. Serum NGAL was measured using a Biosite Triage point-of-care monitor at 5 time points after injury.

RESULTS

Neutrophil gelatinase-associated lipocalin rose in both groups of casualties and was significantly predictive of death or renal failure at intensive care unit admission, 12 and 24 hours after injury.

CONCLUSIONS

Neutrophil gelatinase-associated lipocalin is not a specific marker of blast injury but is predictive of both renal failure and poor outcome.

Blast injury research models

Blast injuries are an increasing problem in both military and civilian practice. Primary blast injury to the lungs (blast lung) is found in a clinically significant proportion of casualties from explosions even in an open environment, and in a high proportion of severely injured casualties following explosions in confined spaces. Blast casualties also commonly suffer secondary and tertiary blast injuries resulting in significant blood loss. The presence of hypoxaemia owing to blast lung complicates the process of fluid resuscitation. Consequently, prolonged hypotensive resuscitation was found to be incompatible with survival after combined blast lung and haemorrhage. This article describes studies addressing new forward resuscitation strategies involving a hybrid blood pressure profile (initially hypotensive followed later by normotensive resuscitation) and the use of supplemental oxygen to increase survival and reduce physiological deterioration during prolonged resuscitation. Surprisingly, hypertonic saline dextran was found to be inferior to normal saline after combined blast injury and haemorrhage. New strategies have therefore been developed to address the needs of blast-injured casualties and are likely to be particularly useful under circumstances of enforced delayed evacuation to surgical care.

Traumatic brain injury

There is an increasing incidence of military traumatic brain injury (TBI), and similar injuries are seen in civilians in war zones or terrorist incidents. Indeed, blast-induced mild TBI has been referred to as the signature injury of the conflicts in Iraq and Afghanistan. Assessment involves schemes that are common in civilian practice but, in common with civilian TBI, takes little account of information available from modern imaging (particularly diffusion tensor magnetic resonance imaging) and emerging biomarkers. The efficient logistics of clinical care delivery in the field may have a role in optimizing outcome. Clinical care has much in common with civilian TBI, but intracranial pressure monitoring is not always available, and protocols need to be modified to take account of this. In addition, severe early oedema has led to increasing use of decompressive craniectomy, and blast TBI may be associated with a higher incidence of vasospasm and pseudoaneurysm formation. Visual and/or auditory deficits are common, and there is a significant risk of post-traumatic epilepsy. TBI is rarely an isolated finding in this setting, and persistent post-concussive symptoms are commonly associated with post-traumatic stress disorder and chronic pain, a constellation of findings that has been called the polytrauma clinical triad.

Blast mines: physics, injury mechanisms and vehicle protection

Since World War II, more vehicles have been lost to land mines than all other threats combined. Anti-vehicular (AV) mines are capable of disabling a heavy vehicle, or completely destroying a lighter vehicle. The most common form of AV mine is the blast mine, which uses a large amount of explosive to directly damage the target. In a conventional military setting, landmines are used as a defensive force-multiplier and to restrict the movements of the opposing force. They are relatively cheap to purchase and easy to acquire, hence landmines are also potent weapons in the insurgents' armamentarium. The stand-offnature of its design has allowed insurgents to cause significant injuries to security forces in current conflicts with little personal risk. As a result, AV mines and improvised explosive devices (IEDs) have become the most common cause of death and injury to Coalition and local security forces operating in Iraq and Afghanistan. Detonation of an AV mine causes an explosive, exothermic reaction which results in the formation of a shockwave followed by a rapid expansion of gases. The shockwave is mainly reflected by the soillair interface and fractures the soil cap overthe mine. The detonation products then vent through the voids in the soil, resulting in a hollow inverse cone which consists of the detonation gases surrounded by the soil ejecta. It is the combination of the detonation products and soil ejecta that interact with the target vehicle and cause injury to the vehicle occupants. A number of different strategies are required to mitigate the blast effects of an explosion. Primary blast effects can be reduced by increasing the standoff distance between the seat of the explosion and the crew compartment. Enhancement of armour on the base of the vehicle, as well as improvements in personal protection can prevent penetration of fragments. Mitigating tertiary effects can be achieved by altering the vehicle geometry and structure, increasing vehicle mass, as well as developing new strategies to reduce the transfer of the impulse through the vehicle to the occupants. Protection from thermal injury can be provided by incorporating fire resistant materials into the vehicle and in personal clothing. The challenge for the vehicle designer is the incorporation of these protective measures within an operationally effective platform.

Relationship between orientation to a blast and pressure wave propagation inside the rat brain

Exposure to a blast wave generated during an explosion may result in brain damage and related neurological impairments. Several mechanisms by which the primary blast wave can damage the brain have been proposed, including: (1) a direct effect of the shock wave on the brain causing tissue damage by skull flexure and propagation of stress and shear forces; and (2) an indirect transfer of kinetic energy from the blast, through large blood vessels and cerebrospinal fluid (CSF), to the central nervous system. To address a basic question related to the mechanisms of blast brain injury, pressure was measured inside the brains of rats exposed to a low level of blast (~35kPa), while positioned in three different orientations with respect to the primary blast wave; head facing blast, right side exposed to blast and head facing away from blast. Data show different patterns and durations of the pressure traces inside the brain, depending on the rat orientation to blast. Frontal exposures (head facing blast) resulted in pressure traces of higher amplitude and longer duration, suggesting direct transmission and reflection of the pressure inside the brain (dynamic pressure transfer). The pattern of the pressure wave inside the brain in the head facing away from blast exposures assumes contribution of the static pressure, similar to hydrodynamic pressure to the pressure wave inside the brain.

Effects of tissue preservation temperature on high strain-rate material properties of brain

Postmortem preservation conditions may be one of factors contributing to wide material property variations in brain tissues in literature. The objective of present study was to determine the effects of preservation temperatures on high strain-rate material properties of brain tissues using the split Hopkinson pressure bar (SHPB). Porcine brains were harvested immediately after sacrifice, sliced into 2 mm thickness, preserved in ice cold (group A, 10 samples) and 37°C (group B, 9 samples) saline solution and warmed to 37°C just prior to the test. A SHPB with tube aluminum transmission bar and semi-conductor strain gauges were used to enhance transmitted wave signals. Data were gathered using a digital acquisition system and processed to obtain stress-strain curves. All tests were conducted within 4 h postmortem. The mean strain-rate was 2487±72 s(-1). A repeated measures model with specimen-level random effects was used to analyze log transformed stress-strain responses through the entire loading range. The mean stress-strain curves with ±95% confidence bands demonstrated typical power relationships with the power value of 2.4519 (standard error, 0.0436) for group A and 2.2657 (standard error, 0.0443) for group B, indicating that responses for the two groups are significantly different. Stresses and tangent moduli rose with increasing strain levels in both groups. These findings indicate that storage temperatures affected brain tissue material properties and preserving tissues at 37°C produced a stiffer response at high strain-rates. Therefore, it is necessary to incorporate material properties obtained from appropriately preserved tissues to accurately predict the responses of brain using stress analyses models, such as finite element simulations.

Development of a large animal model for investigating resuscitation after blast and hemorrhage

BACKGROUND

Blast injuries are an increasing problem owing to the widespread terrorist threat, but hemorrhage remains the second leading cause of civilian trauma death. Against this background, increasing numbers of prehospital and military trauma organizations are advocating a hypotensive approach to resuscitation of the hypovolemic casualty, deliberately aiming not to achieve a normal blood pressure so as not to disturb any newly formed blood clots at the site of a vascular injury.

METHODS

There are no data available to guide clinicians as to how best to resuscitate the blast-injured casualty who has also suffered a hemorrhagic injury. A large-scale program was initiated to examine this question and to offer clinical guidance on the optimal resuscitation strategy in such circumstances in terms of volume, type of fluid, speed of resuscitation, and appropriate endpoints. Before such experiments could be undertaken, a novel large animal model of blast and hemorrhage had to be devised and validated. This study outlines the derivation of such a large animal model utilizing terminally anesthetized Large White pigs exposed to a standardized primary blast wave followed by a controlled hemorrhage of 30% of the total blood volume.

RESULTS AND CONCLUSION

The preliminary results confirm the reliability and reproducibility of this model.

Blast injuries

Health-care providers are increasingly faced with the possibility of needing to care for people injured in explosions, but can often, however, feel undertrained for the unique aspects of the patient's presentation and management. Although most blast-related injuries (eg, fragmentation injuries from improvised explosive devices and standard military explosives) can be managed in a similar manner to typical penetrating or blunt traumatic injuries, injuries caused by the blast pressure wave itself cannot. The blast pressure wave exerts forces mainly at air-tissue interfaces within the body, and the pulmonary, gastrointestinal, and auditory systems are at greatest risk. Arterial air emboli arising from severe pulmonary injury can cause ischaemic complications-especially in the brain, heart, and intestinal tract. Attributable, in part, to the scene chaos that undoubtedly exists, poor triage and missed diagnosis of blast injuries are substantial concerns because injuries can be subtle or their presentation can be delayed. Management of these injuries can be a challenge, compounded by potentially conflicting treatment goals. This Seminar aims to provide a thorough overview of these unique primary blast injuries and their management.

Blast Lung Injury

Current trends in global terrorism mandate that emergency medical services, emergency medicine and other acute care clinicians have a basic understanding of the physics of explosions, the types of injuries that can result from an explosion, and current management for patients injured by explosions. High-order explosive detonations result in near instantaneous transformation of the explosive material into a highly pressurized gas, releasing energy at supersonic speeds. This results in the formation of a blast wave that travels out from the epicenter of the blast. Primary blast injuries are characterized by anatomical and physiological changes from the force generated by the blast wave impacting the body's surface, and affect primarily gas-containing structures (lungs, gastrointestinal tract, ears). "Blast lung" is a clinical diagnosis and is characterized as respiratory difficulty and hypoxia without obvious external injury to the chest. It may be complicated by pneumothoraces and air emboli and may be associated with multiple other injuries. Patients may present with a variety of symptoms, including dyspnea, chest pain, cough, and hemoptysis. Physical examination may reveal tachypnea, hypoxia, cyanosis, and decreased breath sounds. Chest radiography, computerized tomography, and arterial blood gases may assist with diagnosis and management; however, they should not delay diagnosis and emergency interventions in the patient exposed to a blast. High flow oxygen, airway management, tube thoracostomy in the setting of pneumothoraces, mechanical ventilation (when required) with permissive hypercapnia, and judicious fluid administration are essential components in the management of blast lung injury.

Medical consequences of suicide bombing mass casualty incidents: the impact of explosion setting on injury patterns

BACKGROUND

The increase in the incidence of suicide bombings on urban civilian populations in the recent years necessitates a better understanding of the related epidemiology in order to improve the outcome of future casualties.

OBJECTIVE

To characterise the epidemiology of mass casualty incidents following suicide explosions in relation to the surrounding settings.

METHODS

This study presents an analysis of the immediate medical consequences of 12 consecutive multiple casualty incidents (MCI's). Both pre-hospital and in-hospital data was assessed for each event including EMS evacuation times, types of injuries, body regions involved, Emergency Department (ED) triage, ED interventions and surgical procedures performed.

RESULTS

The average arrival time of the first ambulance to the scene was 6.8+/-2.3 min. The first "urgent" patient was evacuated in average of 7.6+/-5.3 min later, while the last "urgent" patient was evacuated 27.8+/-7.9 min after the explosion. Explosions that occurred in buses had the worst rates of overall mortality (21.2%). However, those who survived closed space explosions suffered from the highest number of severe and moderate (ISS>8) injuries (22.9%). Casualties in this group underwent the largest number of both Emergency Room and Surgical interventions. Of the three settings, open space explosions resulted in the largest numbers of casualties with the smallest percentage of severe injuries or death.

CONCLUSIONS

MCIs resulting from suicide explosions can be classified according to the setting of the event since each group was found to have distinct epidemiological characteristics.

Primary blast injury: update on diagnosis and treatment

BACKGROUND

: Injuries from combat and terrorist explosions are increasing worldwide. As such, physicians can expect to treat more patients with complex and unique patterns of injury produced not only by fragments and blunt trauma, but also by high-pressure air expanding from the detonation center.

DISCUSSION

: Tissue damage from the blast wave or primary blast injury can be an important cause of occult trauma to the ocular, aural, pulmonary, cardiovascular, musculoskeletal, and neurologic systems. Awareness of the extensive corporal effects of the blast wave is an essential prerequisite to diagnosis.

SUMMARY

: This article focuses on the incidence, risk factors, diagnosis, management, and screening for primary blast injury.

Tympanic membrane perforation and hearing loss from blast overpressure in Operation Enduring Freedom and Operation Iraqi Freedom wounded

BACKGROUND

Tympanic membrane perforation is the most common primary blast injury in the current conflicts and occurs in approximately one tenth of service members wounded by combat explosions. We wanted to determine the severity of perforation and its effect on hearing and combat readiness.

METHODS

This analysis is a retrospective study of US service members injured in combat explosions in Afghanistan or Iraq and treated at our institution between March 2003 and July 2006. Data captured included location and grade of perforation, symptoms, healing rates, audiogram results, need for hearing aids, and loss of eligibility for military service.

RESULTS

Of 436 explosion-wounded patients admitted to our facility, 65 (15%) patients had tympanic membrane perforation diagnosed by the otolaryngology service. A total of 97 tympanic membrane perforations occurred among 65 patients. The average surface area involved was 41% +/- 32% (right) and 35% +/- 34% (left). More than one third of perforations were grade 4. The most common locations were central and anterior-inferior. Most (83%) patients reported symptoms, most commonly diminished hearing (77%) and tinnitus (50%). Outcome data were available for 77% of perforations. Spontaneous healing occurred in 48%. The remainder (52%) had surgical intervention. The most common audiogram abnormality was mild high frequency hearing loss. Ultimately, three patients (5%) required hearing aids and one discharge from military service.

CONCLUSIONS

Tympanic membrane perforation occurs in 16% of explosion-injured patients. Most patients are symptomatic and many have large perforations requiring operative intervention. Long-term hearing loss is uncommon but does impact ability to continue military service.