Histologic, immunohistochemical, and ultrastructural findings in human blast lung injury

Post-blast histological changes to three animal bones exposed to close-range chemical detonation

A range of investigative practices to aid explosive-related death investigations currently exist, although the use of histopathological bone samples to diagnose blast exposure and the distance of individuals from the blast source has not been previously reported. Forensic histopathology has been used effectively on soft tissue samples to define blast-related injuries effectively, analysing human organs such as the lungs, brain, liver, and skeletal muscles, providing important and useful forensic pathology interpretations. However, no studies currently exist examining the post-blast histological changes in human or animal bones subjected to blasts for forensic pathology practice, despite the opportunity that hard tissue bone samples present, given their significantly lower rate of decomposition over soft tissue. This study presents the first evidence-based findings on the post-blast histological changes in three animal bones when exposed to close-range chemical detonation (C4). The study's qualitative findings highlight critical changes in the tissue architecture of three different animal bone sources due to blast effects with range from the blast source. This emphasises the potential use of histopathological bone sample analysis in future blast-related death investigations, while providing ideas to further explore this work using larger-scale experiments and post-blast case studies in aid of applying this work to human samples and forensic pathology practice.

Tensile Overload Injures Human Alveolar Epithelial Cells through YAP/F-Actin/MAPK Signaling

BACKGROUND

Explosion shockwaves can generate overloaded mechanical forces and induce lung injuries. However, the mechanism of lung injuries caused by tensile overload is still unclear.

METHODS

Flow cytometry was used to detect the apoptosis of human alveolar epithelial cells (BEAS-2B) induced by tensile overload, and cell proliferation was detected using 5-ethynyl-2'-deoxyuridine (EdU). Immunofluorescence and Western blot analysis were used to identify the tensile overload on the actin cytoskeleton, proteins related to the mitogen-activated protein kinase (MAPK) signal pathway, and the Yes-associated protein (YAP).

RESULTS

Tensile overload reduced BEAS-2B cell proliferation and increased apoptosis. In terms of the mechanism, we found that tensile overload led to the depolymerization of the actin cytoskeleton, the activation of c-Jun N-terminal kinase (JNK) and extracellular-signal-regulated kinase 1/2 (ERK1/2), and the upregulation of YAP expression. Jasplakinolide (Jasp) treatment promoted the polymerization of the actin cytoskeleton and reduced the phosphorylation of tension-overload-activated JNK and ERK1/2 and the apoptosis of BEAS-2B cells. Moreover, the inhibition of the JNK and ERK1/2 signaling pathways, as well as the expression of YAP, also reduced apoptosis caused by tensile overload.

CONCLUSION

Our study establishes the role of the YAP/F-actin/MAPK axis in tensile-induced BEAS-2B cell injury and proposes new strategies for the treatment and repair of future lung injuries.

EFFECT OF EXOSOMES DERIVED FROM BONE MARROW MESENCHYMAL STEM CELLS ON PROGRAMMED CELL DEATH IN BLAST-INDUCED LUNG INJURY IN RATS

ABSTRACT

Blast lung injuries (BLIs) are frequent because of industrial accidents and terrorist groups. Bone marrow mesenchymal stem cells (BMSCs) and exosomes derived from BMSCs (BMSCs-Exo) have become a hot topic in modern biology because of their significance in damage healing, immune regulation, and gene therapy. The aim of this study is to investigate the effect of BMSCs and BMSCs-Exo on BLI in rats caused by gas explosion. Here, BMSCs and BMSCs-Exo were transplanted into BLI rats via tail vein and then evaluated pathological alterations, oxidative stress, apoptosis, autophagy, and pyroptosis in the lung tissue. Through histopathology and changes in malondialdehyde (MDA) and superoxide dismutase (SOD) contents, we discovered that oxidative stress and inflammatory infiltration in the lungs were significantly reduced by BMSCs and BMSCs-Exo. After treatment with BMSCs and BMSCs-Exo, apoptosis-related proteins, such as cleaved caspase-3 and Bax, were significantly decreased, and the ratio of Bcl-2/Bax was significantly increased; the level of pyroptosis-associated proteins, including NLRP3, GSDMD-N, cleaved caspase-1, IL-1β, and IL-18, were decreased; autophagy-related proteins, beclin-1 and LC3, were downregulated while P62 was upregulated; the number of autophagosomes was decreased. In summary, BMSCs and BMSCs-Exo attenuate BLI caused by gas explosion, which may be associated with apoptosis, aberrant autophagy, and pyroptosis.

Immunopathological Alterations after Blast Injury and Hemorrhage in a Swine Model of Prolonged Damage Control Resuscitation

Trauma-related hemorrhagic shock (HS) remains a leading cause of death among military and civilian trauma patients. We have previously shown that administration of complement and HMGB1 inhibitors attenuate morbidity and mortality 24 h after injury in a rat model of blast injury (BI) and HS. To further validate these results, this study aimed to develop a swine model and evaluate BI+HS-induced pathophysiology. Anesthetized Yucatan minipigs underwent combined BI and volume-controlled hemorrhage. After 30 min of shock, animals received an intravenous bolus of PlasmaLyte A and a continuous PlasmaLyte A infusion. The survival rate was 80% (4/5), and the non-survivor expired 72 min post-BI. Circulating organ-functional biomarkers, inflammatory biomarkers, histopathological evaluation, and CT scans indicated evidence of multiple-organ damage, systemic innate immunological activation, and local tissue inflammation in the injured animals. Interestingly, a rapid and dramatic increase in plasma levels of HMGB1 and C3a and markedly early myocarditis and encephalitis were associated with early death post-BI+HS. This study suggests that this model reflects the immunopathological alterations of polytrauma in humans during shock and prolonged damage control resuscitation. This experimental protocol could be helpful in the assessment of immunological damage control resuscitation approaches during the prolonged care of warfighters.

Characteristics of inflammatory response and repair after experimental blast lung injury in rats

BACKGROUND AND OBJECTIVES

Blast-induced lung injury is associated with inflammatory, which are characterised by disruption of the alveolar-capillary barrier, haemorrhage, pulmonary infiltrateration causing oedema formation, pro-inflammatory cytokine and chemokine release, and anti-inflammatory counter-regulation. The objective of the current study was to define sequence of such alterations in with establishing blast-induced lung injury in rats using an advanced blast generator.

METHODS

Rats underwent a standardized blast wave trauma and were euthanised at defined time points. Non-traumatised animals served as sham controls. Obtained samples from bronchoalveolar lavage fluid (BALF) at each time-point were assessed for histology, leukocyte infiltration and cytokine/chemokine profile.

RESULTS

After blast lung injury, significant haemorrhage and neutrophil infiltration were observed. Similarly, protein accumulation, lactate dehydrogenase activity (LDH), alveolar eicosanoid release, matrix metalloproteinase (MMP)-2 and -9, pro-Inflammatory cytokines, including tumour necrosis factor (TNF) and interleukin (IL) -6 raised up. While declining in the level of anti-inflammatory cytokine IL-10 occurred. Ultimately, pulmonary oedema developed that increased to its maximum level within the first 1.5 h, then recovered within 24 h.

CONCLUSION

Using a stablished model, can facilitate the study of inflammatory response to blast lung injury. Following the blast injury, alteration in cytokine/chemokine profile and activity of cells in the alveolar space occurs, which eventuates in alveolar epithelial barrier dysfunction and oedema formation. Most of these parameters exhibit time-dependent return to their basal status that is an indication to resilience of lungs to blast-induced lung injury.

Ex Vivo Pulmonary Oedema after In Vivo Blast-Induced Rat Lung Injury: Time Dependency, Blast Intensity and Beta-2 Adrenergic Receptor Role

Objective: Current treatments for blast-induced lung injury are limited to supportive procedures including mechanical ventilation. The study aimed to investigate the role of post-trauma-induced oedema generation in the function of time and trauma intensity and the probable role of beta 2-adrenergic receptors (β2-ARs) agonists on pulmonary oedema. The study is conducted using an ex vivo model after an experimental in vivo blast-induced thorax trauma in rats. Methods: Rats were randomised and divided into two groups, blast and sham. The blast group were anaesthetised and exposed to the blast wave (3.16 ± 0.43 bar) at a distance of 3.5 cm from the thorax level. The rats were sacrificed 10 min after the blast, the lungs explanted and treated with terbutaline, formoterol, propranolol or amiloride to assess the involvement of sodium transport. Other groups of rats were exposed to distances of 5 and 7 cm from the thorax to reduce the intensity of the injury. Further, one group of rats was studied after 180 min and one after 360 min after a 3.5 cm blast injury. Sham controls were exposed to identical procedures except for receiving blast overpressure. Results: Lung injury and oedema generation depended on time after injury and injury intensity. Perfusion with amiloride resulted in a further increase in oedema formation as indicated by weight gain (p < 0.001), diminished tidal volume (Tv) (p < 0.001), and increased airway resistance (p < 0.001). Formoterol caused a significant increase in the Tv (p < 0.001) and a significant decrease in the airway resistance (p < 0.01), while the lung weight was not influenced. Trauma-related oedema was significantly reduced by terbutaline in terms of lung weight gain (p < 0.01), Tv (p < 0.001), and airway resistance (p < 0.01) compared to control blast-injured lungs. Terbutaline-induced effects were completely blocked by the β-receptor antagonist propranolol (p < 0.05). Similarly, amiloride, which was added to terbutaline perfusion, reversed terbutaline-induced weight gain reduction (p < 0.05). Conclusions: β2-adrenoceptor stimulation had a beneficial impact by amiloride-dependent sodium and therefore, fluid transport mechanisms on the short-term ex vivo oedema generation in a trauma-induced in vivo lung injury of rats.

Ventilating the blast lung: Exploring ventilation strategies in primary blast lung injury

Introduction

Primary blast lung injury (PBLI) is the most common and fatal of all primary blast injuries. The majority of those with PBLI will require early intubation and mechanical ventilation, and thus, ventilation strategy forms a crucial part of any management plan. Methods: A comprehensive, but not systematic, PubMed and Google Scholar database search identified articles that contribute to our current understanding of ventilation strategies in PBLI for a narrative educational review.

Results

A PBLI ventilation strategy must strive to minimise all four of ventilator-associated lung injury (VALI), volutrauma, barotrauma and biotrauma. The three main ventilation strategies available are conventional low tidal volume (LTV) ventilation, airway pressure release ventilation (APRV) and high frequency oscillatory ventilation (HFOV). Conventional LTV ventilation together with a variable positive end-expiratory pressure (PEEP) and permissive hypercapnia has demonstrated reduced inflammation and mortality with a greater number of ventilator-free days. APRV has the potential to reduce dynamic strain, PaO2/FiO2 ratios, levels of applied mechanical power and extravascular lung water while encouraging spontaneous breathing. HFOV is able to effectively avoid VALI while curbing inflammation and histological lung injury, though not necessarily mortality. Conclusions: Presently, PBLI should largely be managed with conventional LTV ventilation alongside a variable PEEP and permissive hypercapnia with APRV and HFOV reserved as rescue strategies for where conventional LTV ventilation fails. Clinicians should additionally consider supplementing their strategy with adjunctive therapies such as prone positioning, inhaled nitric oxide and extracorporeal membrane oxygenation that may further reduce mortality and combat severe respiratory and/or cardiac failure.

Resveratrol ameliorates thoracic blast exposure-induced inflammation, endoplasmic reticulum stress and apoptosis in the brain through the Nrf2/Keap1 and NF-κB signaling pathway

Blast injuries include the various types of internal and external trauma caused by the impact force of high-speed blast waves with multiple mechanisms involved. Thoracic blast exposure could induce neurotrauma as well, but effective therapies are lacking. Resveratrol is a polyphenol flavonoid secreted by plants and has been shown to provide cardiovascular protection and play anti-inflammatory, anti-oxidation and anti-cancer roles. However, the effects of resveratrol on thoracic blast exposure-induced brain injury have not been investigated. To explore this, a mouse model of thoracic blast exposure-induced brain injury was established. Sixty C57BL/6 wild type mice were randomly divided equally into four groups (one control group, one model group, and model groups with 25 or 50 mg/kg resveratrol injected intraperitoneally). As traumatic brain injury often accompanied by mental symptoms, cognitive dysfunction and anxious behavior were evaluated by Y maze, elevated plus maze and open field test. We also examined the mice for histopathological changes by hematoxylin-eosin staining; the expressions of inflammatory-related factors by ELISA; endoplasmic reticulum stress in brain tissue via the generation of reactive oxygen species (ROS) and the expressions of inositol-requiring enzyme-α (IRE-α) and C/EBP homologous protein (CHOP); apoptosis by measuring levels of Bax, p53 and Bcl-2. In addition, proteins of related pathways were also studied by western blotting. We found that resveratrol significantly reduced the levels of inflammatory-related factors, including interleukin (IL)-1β, IL-4, and high mobility group box protein 1(HMGB1), and increased the level of anti-inflammatory-related factor, IL-10, under thoracic blast exposure (P < 0.05). Cognitive dysfunction and anxious behavior were also ameliorated by resveratrol. In brain tissue, resveratrol significantly attenuated thoracic blast exposure-induced generation of ROS and expressions of IRE-α and CHOP, lowered the expressions of Bax and p53, and maintained Bcl-2 expression (P < 0.05). Additionally, resveratrol significantly ameliorated thoracic blast exposure-induced increases of Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor (NF)-κB and the decrease in nuclear factor erythroid 2-related factor 2(Nrf2) expression in the brain (P < 0.05). Our results indicate that resveratrol has a protective effect on thoracic blast exposure-induced brain injury that is likely mediated through the Nrf2/Keap1 and NF-κB signaling pathways.

Forensic considerations on the two major civilian terrorist events occurred in Milan: A retrospective autopsy-based study

Explosion-related deaths are a disregarded topic of forensic sciences, despite the pivotal role of the forensic pathologist in such investigations. In fact, very few scientific articles have been published up to now, even if there is a considerable increase of terrorist attacks worldwide due to the use of improvised explosive devices (IEDs). In this paper, the authors show a retrospective autopsy-based study on the two major civilian terrorist events which occurred in Milan (Italy). The first one took place in a closed system, where a gelignite bomb was set inside the National Agriculture Bank in December 1969. 17 people were killed, and all of them underwent forensic autopsies, which were performed at the Milan Institute of Legal Medicine. The second event took place in an open system, where a car bomb exploded in Palestro Street in July 1993. 5 people were killed, forensic autopsies were performed as well. A total of 22 explosion-related deaths were assessed in this study. For each victim, the analysis of clothes, external and internal examinations were reported; furthermore, a statistical analysis using Fisher's exact test was carried out in order to show differences among blast injuries that occurred in a closed system versus an open system. The analysis of the autopsy reports, which included the descriptions of clothes, and the injury patterns allowed a possible reconstruction of the bodily exposure side of the victims in relation to the origin site of the explosive devices.

Explosion-related deaths: An overview on forensic evaluation and implications

Purpose

Explosion-related deaths are uncommon events which require expertise and confidence so that an appropriate death investigation can be performed. The present study aims to provide a detailed forensic analysis of the issues and implications arising in the event of an explosion.

Methods

A retrospective review of casualty data was conducted on electronic literature databases. Cases concerning deadly explosions registered at the Milan Institute of Legal Medicine were examined and analyzed altogether.

Results

Explosions may involve closed or open systems. A security assessment of the site is always necessary. Alterations of the site due to rescue procedures can occur; thus, on-site forensic investigation should be adapted to the environment. Then, a study protocol based on autopsy procedures is presented. Application of the postmortem radiology enforces forensic procedures both for the analysis of blast injuries and skeleton fractures, and for identification purposes. Blast injuries typically cause lacerations of the lungs, intestine and major vessels; moreover, hyoid fractures can be documented. Histopathology may help to define blast injuries effectively. Forensic chemistry, toxicology and ballistics provide useful investigative evidence as well as anthropology and genetics. Different forensic topics regarding explosions are discussed through five possible scenarios that forensic pathologists may come across. Scenarios include self-inflicted explosion deaths, domestic explosions, work-related explosions, terrorist events, and explosions caused by accidents involving heavy vehicles.

Conclusion

The scenarios presented offer a useful instrument to avoid misinterpretations and evaluation errors. Procedural notes and technical aspects are provided to the readers, with an insight on collaboration with other forensic experts.

An autopsy case of death due to AC compressor blast - A rare case illustrating primary, secondary, tertiary & quaternary blast injuries

Blast injuries seen in various accidents involving pressurized containers like gas cylinders, tires, et cetera, and acts of terrorism. The associated factors can vary from poor handling of equipment to inadequate safety precautions. These injuries include a variety of injuries, such as, injuries due to shock wave, burns, fractures, et cetera, involving multi-organ systems, especially lungs and hollow organs, due to the high-pressurized shock wave. The presented case is of the death of a 24-years-old male as a result of a blast of the compressor present in the AC outdoor unit during the filling of the gas. Here, the body showed injuries due to shock wave, secondary impact, tertiary impact because of fall on the ground, and quaternary injuries due to burns. The cause of death was Blast lung associated with Subarachnoid hemorrhage.

Tanshinone IIA alleviates blast-induced inflammation, oxidative stress and apoptosis in mice partly by inhibiting the PI3K/Akt/FoxO1 signaling pathway

Although Tanshinone IIA (Tan IIA) has been associated with inflammation, oxidative stress and apoptosis, the effects of Tan IIA on lung blast injury remain uncertain. In this study, we explored the effects of Tan IIA on lung blast injury, studied its possible molecular mechanisms. Fifty C57BL/6 mice were randomly divided into the control, blast, blast + Tan IIA, blast + LY294002 (a PI3K inhibitor), or blast + Tan IIA + LY294002 groups. Serum and lung samples were collected 48 h after blast injury. The data showed that Tan IIA significantly inhibited blast-induced increases in the lung weight/body weight and wet/dry (W/D) weight ratios, decreased the CD44^-and CD163-positive inflammatory cell infiltration in the lungs, reduced the IL-1β, TNF-α and IL-6 expression, and enhanced IL-10 expression. Tan IIA also significantly alleviated the increases in MDA5 and IRE-a and the decrease in SOD-1 and reversed the low Bcl-2 expression and the high Bax and Caspase-3 expressions. Additionally, Tan IIA significantly decreased p-PI3K and p-Akt expression and increased p-FoxO1 expression. More importantly, both LY294002 and Tan IIA pretreatment markedly protected against blast-induced inflammation, oxidative stress and apoptosis in lung blast injury. These results suggest that Tan IIA protects against lung blast injury, which may be partly mediated by inhibiting the PI3K/Akt/FoxO1 signaling pathway.

Management of combined massive burn and blast injury: A 20-year experience

INTRODUCTION

Blast injuries are complex types of physical trauma resulting from direct or indirect exposure to an explosion, which can be divided into four classes: primary, secondary, tertiary, and quaternary. Primary blast injury results in damage, principally, in gas-containing organs such as the lungs (blast lung injury, BLI). BLI is defined as radiological and clinical evidence of acute lung injury occurring within 12h of exposure to an explosion and not due to secondary or tertiary injury. BLI often combines with cutaneous thermal injury, a type of quaternary blast injury, either in terrorist bomb attacks or in civilian accidental explosions. This report summarizes our experience in the management of combined massive burn and BLI at a Shanghai Burn Center in China.

METHODS

A retrospective observational analysis of clinical data was performed for massive burn patients with or without BLI during a 20-year interval. Patient characteristics, causes of injury, clinical parameters, management, and outcomes were recorded and evaluated.

RESULTS

A total of 151 patients (120 males and 31 females) with severe burn injury (≥50% TBSA) treated at the Burn Center of Changhai Hospital in Shanghai between July 1997 and June 2017 were enrolled in this study. Their mean age was 38.6±17.8 (3-75) years. Among them, 28 patients had combined BLI and burn injury and 39 patients had no BLI or smoke inhalation injury (non-BLI-SII). No significant difference was observed in the burn area or full-thickness burn area between the two groups. The lowest PaO₂/fraction of inspired oxygen (FiO₂) ratio during the first 24h in BLI patients was significantly lower than that in non-BLI-SII patients. Exudative changes were observed by X-ray radiography in all BLI patients but not in non-BLI-SII patients within 6h after injury. A significantly higher proportion of colloids were used for fluid resuscitation in BLI patients than that in non-BLI-SII patients. A higher proportion and longer time of mechanical ventilation were needed for BLI patients than those for non-BLI-SII patients, and a higher proportion of patients received sedative agents in the BLI group than those in the non-BLI-SII group. The first escharectomy was performed relatively later in BLI patients than in non-BLI-SII patients because of more time taken by BLI patients to recover from lung injury. The length of ICU and hospital stay in BLI patients was significantly longer than that in non-BLI-SII patients. No significant difference in the overall mortality was detected between these two groups.

CONCLUSION

It is a formidable challenge for clinicians to diagnose and manage massive burn patients combined with BLI. A comprehensive treatment approach is strongly recommended, including fluid resuscitation, airway management, mechanical ventilation, and surgical treatment. Given the high mortality of massive burn patients combined with BLI even in a recognized burn center, more prospective studies are encouraged to assess more effective strategies for the treatment of such patients.

Thoracic Injury in Patients Injured by Explosions on the Battlefield and in Terrorist Incidents

Thoracic injury is common on the battlefield and in terrorist attacks, occurring in 10% to 70% of patients depending on the type of weapons used. Typical injuries seen include bullet, blast, and fragment injuries to the thorax, which are often associated with injuries to other parts of the body. Initial treatment prehospital and in the ED is carried out according to the principles of Tactical Combat Casualty Care or other standard trauma management systems. Immediately life-threatening problems including catastrophic hemorrhage are dealt with rapidly, and early consideration is given to CT scanning or rapid surgical intervention where appropriate. All patients should be given lung-protective ventilation. Treatment of these patients in the critical care unit is complicated by the severity of associated injuries and by features specific to combat trauma including blast lung injury, a high incidence of delirium, unusual infections such as colonization with multidrug-resistant Acinetobacter baumannii complex, and sometimes invasive fungal infections. A minority of patients with blast lung injury in published series have been successfully treated with prolonged respiratory support with high-frequency oscillatory ventilation and extracorporeal membrane oxygenation. The role of newer treatment options such as resuscitative endovascular balloon occlusion of the aorta is not yet known. In this article we review the relatively sparse literature on this group of patients and provide practical advice based on the literature and our institution's extensive experience of managing battlefield casualties.

Effects of adjunct treatments on end-organ damage and histological injury severity in acute respiratory distress syndrome and multiorgan failure caused by smoke inhalation injury and burns

BACKGROUND

We investigated effects of mesenchymal stem cells (MSC) or low-flow extracorporeal life support (ECLS) as adjunctive treatments for acute respiratory distress syndrome (ARDS) due to inhalation injury and burns. We hypothesized that these interventions decrease histological end-organ damage.

METHODS

Anesthetized female swine underwent smoke inhalation injury and 40% TBSA burns, then critical care for 72h. The following groups were studied: CTR (no injury, n = 4), ICTR (injured untreated, n = 10), Allo (injured treated with allogenic MSC, n = 10), Auto (injured treated with autologous MSC, n = 10), Hemo (injured and treated with the Hemolung low flow ECLS system, n = 9), and Nova (injured and treated with the NovaLung low flow ECLS system, n = 8). Histology scores from lung, kidneys, liver, and jejunum were calculated. Data are presented as means±SEM.

RESULTS

Survival at 72h was 100% in CTR; 40% in ICTR; 50% in Allo; 90% in Auto; 33% in Hemo; 63% in Nova. ARDS developed in 0/10 CTR; 10/10 ICTR; 8/9 Hemo; 5/8 Nova; 9/10 Allo; 6/10 Auto. Diffuse alveolar damage (DAD) was present in all injured groups. MSC groups had significantly lower DAD scores than ICTR animals (Allo 26.6 ± 3.4 and Auto 18.9 ± 1.5 vs. ICTR 46.8 ± 2.1, p < 0.001). MSC groups also had lower DAD scores than ECLS animals (Allo vs. Nova, p < 0.05, Allo vs. Hemo p < 0.001, Auto vs. Nova p < 0.001, Auto vs. Hemo, p < 0.001). Kidney injury ICTR (p < 0.05) and Hemo (p < 0.01) were higher than in CTR. By logistic regression, a PaO₂-to-FiO₂ ratio (PFR) < 300 was a function of the DAD score: logit (PFR < 300) = 0.84 + 0.072*DAD Score, odds ratio 1.074 (1.007, 1.147, p < 0.05) with a ROC AUC of 0.76, p < 0.001.

CONCLUSION

Treatment with Auto MSC followed by Allo and then Nova were most effective in mitigating ARDS and MOF severity in this model. Further studies will elucidate the role of combination therapies of MSC and ECLS as comprehensive treatments for ARDS and MOF.

Computational Modeling of Primary Blast Lung Injury: Implications for Ventilator Management

Primary blast lung injury (PBLI) caused by exposure to high-intensity pressure waves is associated with parenchymal tissue injury and severe ventilation-perfusion mismatch. Although supportive ventilation is often required in patients with PBLI, maldistribution of gas flow in mechanically heterogeneous lungs may lead to further injury due to increased parenchymal strain and strain rate, which are difficult to predict in vivo. In this study, we developed a computational lung model with mechanical properties consistent with healthy and PBLI conditions. PBLI conditions were simulated with bilateral derecruitment and increased perihilar tissue stiffness. As a result of these tissue abnormalities, airway flow was heterogeneously distributed in the model under PBLI conditions, during both conventional mechanical ventilation (CMV) and high-frequency oscillatory ventilation. PBLI conditions resulted in over three-fold higher parenchymal strains compared to the healthy condition during CMV, with flow distributed according to regional tissue stiffness. During high-frequency oscillatory ventilation, flow distribution became increasingly heterogeneous and frequency-dependent. We conclude that the distribution and rate of parenchymal distension during mechanical ventilation depend on PBLI severity as well as ventilatory modality. These simulations may allow realistic assessment of the risks associated with ventilator-induced lung injury following PBLI, and facilitate the development of alternative lung-protective ventilation modalities.

Simulation of blast lung injury induced by shock waves of five distances based on finite element modeling of a three-dimensional rat

Blast lung injury (BLI) caused by both military and civilian explosions has become the main cause of death for blast injury patients. By building three-dimensional (3D) models of rat explosion regions, we simulated the surface pressure of the skin and lung. The pressure distributions were performed at 5 distances from the detonation center to the center of the rat. When the distances were 40 cm, 50 cm, 60 cm, 70 cm and 80 cm, the maximum pressure of the body surface were 634.77kPa, 362.46kPa, 248.11kPa, 182.13kPa and 109.29kPa and the surfaces lung pressure ranges were 928–2916 Pa, 733–2254 Pa, 488–1236 Pa, 357–1189 Pa and 314–992 Pa. After setting 6 virtual points placed on the surface of each lung lobe model, simulated pressure measurement and corresponding pathological autopsies were then conducted to validate the accuracy of the modeling. For the both sides of the lung, when the distance were 40 cm, 50 cm and 60 cm, the Pearson’s values showed strong correlations. When the distances were 70 cm and 80 cm, the Pearson’s values showed weak linear correlations. This computational simulation provided dynamic anatomy as well as functional and biomechanical information.

Blast injures to the thorax

One out of 10 of military casualties and 6-9 out of 10 civilian victims of terror incidents suffer pulmonary blast injuries when the attackers use explosives as weapon. No specific therapy exists for the primary, shock-wave injury to the lung. The treatment protocols are based on mechanical ventilation, intensive therapy and supportive care. Secondary and tertiary blast structural injuries to the thorax require damage control surgery, dominated by pleural space management (drainage) and haemorrhage control (thoracotomy if needed). Parenchyma resection of irreversibly destroyed lung is rarely needed, and non-anatomical resections are to be preferred. Delayed chest wall reconstruction follows haemodynamic stabilisation and completion of demarcation process. Blast injury to the chest requires a multidisciplinary approach, where the outcome is strongly influenced by the concomitant injuries.

CD28 Deficiency Ameliorates Thoracic Blast Exposure-Induced Oxidative Stress and Apoptosis in the Brain through the PI3K/Nrf2/Keap1 Signaling Pathway

Blast exposure is a worldwide public health concern, but most related research has been focused on direct injury. Thoracic blast exposure-induced neurotrauma is a type of indirect injuries where research is lacking. As CD28 stimulates T cell activation and survival and contributes to inflammation initiation, it may play a role in thoracic blast exposure-induced neurotrauma. However, it has not been investigated. To explore the effects of CD28 on thoracic blast exposure-induced brain injury and its potential molecular mechanisms, a mouse model of thoracic blast exposure-induced brain injury was established. Fifty C57BL/6 wild-type (WT) and fifty CD28 knockout (CD28^-/-) mice were randomly divided into five groups (one control group and four model groups), with ten mice (from each of the two models) for each group. Lung and brain tissue and serum samples were collected at 12 h, 24 h, 48 h, and 1 week after thoracic blast exposure. Histopathological changes were detected by hematoxylin-eosin staining. The expressions of inflammatory-related factors were detected by ELISA. Oxidative stress in the brain tissue was evaluated by determining the generation of reactive oxygen species (ROS) and the expressions of thioredoxin (TRX), malondialdehyde (MDA), SOD-1, and SOD-2. Apoptosis in the brain tissue was evaluated by TUNEL staining and the levels of Bax, Bcl-xL, Bad, Cytochrome C, and caspase-3. In addition, proteins of related pathways were also studied by western blotting and immunofluorescence. We found that CD28 deficiency significantly reduced thoracic blast exposure-induced histopathological changes and decreased the levels of inflammatory-related factors, including IL-1β, TNF-α, and S100β. In the brain tissue, CD28 deficiency also significantly attenuated thoracic blast exposure-induced generation of ROS and expressions of MDA, TRX, SOD-1, and SOD-2; lowered the number of apoptotic cells and the expression of Bax, cleaved caspase-3, Cytochrome C, and Bad; and maintained Bcl-xL expression. Additionally, CD28 deficiency significantly ameliorated thoracic blast exposure-induced increases of p-PI3K and Keap1 and the decrease of Nrf2 expression in the brain. Our results indicate that CD28 deficiency has a protective effect on thoracic blast exposure-induced brain injury that might be associated with the PI3K/Nrf2/Keap1 signaling pathway.

Understanding blast-induced neurotrauma: how far have we come?

Blast injuries, including blast-induced neurotrauma (BINT), are caused by blast waves generated during an explosion. Accordingly, their history coincides with that of explosives. Hence, it is intriguing that, after more than 1000 years of using explosives, our understanding of the pathological consequences of blast and body/brain interactions is extremely limited. Postconflict recovery mechanisms seemingly include the suppression of painful experiences, such as explosive injuries. Unfortunately, ignoring the knowledge generated by previous generations of scientists retards research progress, leading to superfluous and repetitive studies. This article summarizes clinical and experimental findings published about blast injuries and BINT following the wars of the 20th and 21th centuries. Moreover, it offers a personal view on potential factors interfering with the progress of BINT research working toward providing better diagnosis, treatment and rehabilitation for military personnel affected by blast exposure.

CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury

BACKGROUND

Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung, including the monocyte response, and investigate distal subacute immune effects in the spleen and liver 6 hours after injury.

METHODS

Rats were subjected to a shock wave (~135 kPa overpressure, 2 ms duration) inducing PBLI or sham procedure. Rat physiology was monitored, and at 1, 3, and 6 hours thereafter, blood, lung, and bronchoalveolar lavage fluid (BALF) were collected and analyzed by flow cytometry, enzyme-linked immunosorbent assay, and histologic examination. In addition, at 6 hours, spleen and liver were collected and analyzed by flow cytometry.

RESULTS

Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, interleukin 6 (IL-6), tumor necrosis factor α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung "nonclassical" monocyte and in natural killler, B, or T cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and monocyte chemoattractant protein-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6 hours.

CONCLUSION

This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes, in addition to neutrophils, in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6 hours. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess, or attenuate the immune response in blast-injured patients.

Controlled single bubble cavitation collapse results in jet-induced injury in brain tissue

Multiscale damage due to cavitation is considered as a potential mechanism of traumatic brain injury (TBI) associated with explosion. In this study, we employed a TBI relevant hippocampal ex vivo slice model to induce bubble cavitation. Placement of single reproducible seed bubbles allowed control of size, number, and tissue location to visualize and measure deformation parameters. Maximum strain value was measured at 45 µs after bubble collapse, presented with a distinct contour and coincided temporally and spatially with the liquid jet. Composite injury maps combined this maximum strain value with maximum measured bubble size and location along with histological injury patterns. This facilitated the correlation of bubble location and subsequent jet direction to the corresponding regions of high strain which overlapped with regions of observed injury. A dynamic threshold strain range for tearing of cerebral cortex was estimated to be between 0.5 and 0.6. For a seed bubble placed underneath the hippocampus, cavitation induced damage was observed in hippocampus (local), proximal cerebral cortex (marginal) and the midbrain/forebrain (remote) upon histological evaluation. Within this test model, zone of cavitation injury was greater than the maximum radius of the bubble. Separation of apposed structures, tissue tearing, and disruption of cellular layers defined early injury patterns that were not detected in the blast-exposed half of the brain slice. Ultrastructural pathology of the neurons exposed to cavitation was characterized by disintegration of plasma membrane along with loss of cellular content. The developed test system provided a controlled experimental platform to study cavitation induced high strain deformations on brain tissue slice. The goal of the future studies will be to lower underpressure magnitude and cavitation bubble size for more sensitive evaluation of injury.

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.

Pathogenesis, diagnosis and treatment of cerebral fat embolism

In this study, we analyzed two cases of pure cerebral fat embolism and reviewed related literatures to explore the pathogenesis, clinical manifestations, diagnosis and treatment of cerebral fat embolism, improve the treatment efficiency and reduce the misdiagnosis rate. In our cases, patients fully returned to consciousness at the different times with good prognosis, normal vital signs and without obvious sequelae. For patients with the limb fractures, who developed coma without chest distress, dyspnea or other pulmonary symptoms 12 or 24 h post injury, cerebral fat embolism should be highly suspected, except for those with intracranial lesions, such as delayed traumatic intracerebral hemorrhage, etc. The early diagnosis and comprehensive treatment can improve prognosis.

“Gas and Fat Embolic Syndrome” Involving a Mass Stranding of Beaked Whales (Family Ziphiidae) Exposed to Anthropogenic Sonar Signals

A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.

Noradrenalin effectively rescues mice from blast lung injury caused by laser-induced shock waves

Background

Blast lung injuries (BLI) caused by blast waves are extremely critical in the prehospital setting, and hypotension is thought to be the main cause of death in such cases. The present study aimed to elucidate the pathophysiology of severe BLI using laser-induced shock wave (LISW) and identify the initial treatment.

Methods

The current investigation comprised two parts. For the validation study, mice were randomly allocated to groups that received a single shot of 1.2, 1.3, or 1.4 J/cm² LISW to both lungs. The survival rates, systolic blood pressure (sBP), heart rate (HR), peripheral oxyhemoglobin saturation (SpO₂), and shock index were monitored for 60 min, and lung tissues were analyzed histopathologically. The study evaluated the effects of catecholamines as follows. Randomly assigned mice received 1.4 J/cm² LISW followed by the immediate intraperitoneal administration of dobutamine, noradrenalin, or normal saline. The primary outcome was the survival rate. Additionally, sBP, HR, SpO₂, and the shock index were measured before and 5 and 10 min after LISW, and the cardiac output, left ventricular ejection fraction, and systemic vascular resistance (SVR) were determined before and 1 min after LISW.

Results

The triad of BLI (hypotension, bradycardia, and hypoxemia) was evident immediately after LISW. The survival rates worsened with increasing doses of LISW (100 % in 1.2 J/cm² vs. 60 % in 1.3 J/cm², 10 % in 1.4 J/cm²). The histopathological findings were compatible with those of human BLI. The survival rate in LISW high group (1.4 J/cm²) was highest in the group that received noradrenalin (100 %), with significantly elevated SVR values (from 565 to 1451 dyn s/min⁵). In contrast, the survival rates in the dobutamine and normal saline groups were 40 and 10 %, respectively, and the SVR values did not change significantly after LISW in either group.

Conclusions

The main cause of death during the initial phase of severe BLI is hypotension due to the absence of peripheral vasoconstriction. Therefore, the immediate administration of noradrenalin may be an effective treatment during the initial phase of severe BLI.

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.

Blast overpressure after tire explosion: a fatal case

Fatal blast injuries are generally reported in literature as a consequence of the detonation of explosives in war settings. The pattern of lesion depends on the position of the victim in relation to the explosion, on whether the blast tracks through air or water, and whether it happens in the open air or within an enclosed space and the distance from the explosion. Tire explosion-related injuries are rarely reported in literature. This study presents a fatal case of blast overpressure due to the accidental explosion of a truck tire occurring in a tire repair shop. A multidisciplinary approach to the fatality involving forensic pathologists and engineers revealed that the accidental explosion, which caused a series of primary and tertiary blast wave injuries, was due to tire deterioration.

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.

Accidental death involving professional fireworks

An interesting case of accidental death involving the explosion of professional fireworks in an apartment is described. The examination of the scene permitted to study several effects of the explosion on walls, ceiling, furniture and especially on a balcony where the victim was found. The external examination of the victim showed extensive thermal injuries, degloving injuries and extensive shrapnel wounds. The autopsy examination showed subarachnoid haemorrhage localized to the cerebellum, haemorrhage in the soft tissues of the neck and chest and fracture of one clavicle. Almost the entire surface of lungs showed blunt injuries and the liver showed tearing of parenchyma and multiple cavities. Histological analysis were carried out showing thickening of alveolar septae, enlargement of alveolar spaces and alveolar ruptures in lung sections while numerous, round, empty spaces were detected in the parenchyma of the liver. The examination of the scene and of the fragments found showed that at least eight pyrotechnical charges exploded on the balcony, in close proximity of the threshold with the living room of the apartment. According to the chemical findings, the charges were typical for professional use and were filled with a mixture of potassium perchlorate and aluminium. A conservative calculation results in more than 1.5 kg total mass of pyrotechnic composition exploding very close to the victim.

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.

Lung injury similar to blast lung in a case of shotgun wound of the head

Primary blast lung injury after explosions has been well described in the literature. A case of injury to the lung, after a shotgun wound to the head, similar to primary blast lung, is presented. Histological appearances of the lung revealed alveolar over distension, rupture and intra-alveolar hemorrhage. Primary blast lung injury is considered the reserve of high-order explosives; however, this case reveals similar injuries from a shotgun (low-order explosive), which has not been reported before to the best of our knowledge.

A minimally invasive technique for the detection and analysis of pulmonary fat embolism: a feasibility study

We investigated the feasibility of postmortem percutaneous needle biopsy (PNB) for obtaining pulmonary samples adequate for the study of pulmonary fat embolism (PFE). Samples of both lungs were obtained from 26 cadavers via two different methods: (i) PNB and (ii) the double-edged knife technique, the gold standard at our institute. After water storage and Sudan III staining, six forensic pathologists independently examined all samples for the presence and severity of PFE. The results were compared and analyzed in each case regarding the vitality of the PFE and its relationship to the cause of death. The results showed that PFE was almost identically diagnosed and graded on the samples obtained via both methods. The discrepancies between the two techniques did not affect the diagnoses of vitality or cause of death related to PFE. This study demonstrates the feasibility of the PNB sampling method for the diagnosis and interpretation of PFE in the postmortem setting.

Injury pattern of suicide bomb attacks in Pakistan

PURPOSE

The aim of our study was to analyze the pattern of injuries, hospital care, and outcome of the victims of suicide bomb attacks in Pakistan.

METHODS

This prospective, cohort study was conducted at the Combined Military Hospital Rawalpindi during the last 3 years. Seriously injured patients in the "immediate category" were resuscitated in the emergency operation theater adjacent to the emergency room and, after resuscitation, the patients were transferred to the main operation theaters, where consultant surgeons were available.

RESULTS

During the study period, 1,296 terrorist victims presented to the emergency department and (86.9%) were admitted, with a mean hospital stay of 8.2 ± 2.1 days. The majority of patients arrived by ambulance (91%) and only 38 (3%) were evacuated by air. Penetrating splinter injuries were the most prevalent (87%), and 29% patients also had associated injuries. Open bone fractures were found in 48% and 42% had injured hollow and solid viscous. Overall, 33% of patients had thoracic injuries and neuro-trauma was observed in 16% of the study population. Deafness was a feature in 33% patients, 121 had to undergo limb amputations, and mortality remained in 7% of patients.

CONCLUSION

Most of the problems encountered were logistic in nature. Early evacuation of the victims remains pivotal in saving lives. The major causes of death in peripheral patients was hypovolemic shock, sepsis, and hypothermia. Mortality and morbidity can be enhanced by ample fluid resuscitation, tetanus prophylaxis, and proficient first aid at the site of injury.

[Blast lung injuries]

In armed conflicts and during terrorist attacks, explosive devices are a major cause of mortality. The lung is one of the organs most sensitive to blasts. Thus, today it is important that every GP at least knows the basics and practices regarding treatment of blast victims. We suggest, following a review of the explosions and an assessment of the current threats, detailing the lung injuries brought about by the explosions and the main treatments currently recommended.

Drosophila melanogaster larvae as a model for blast lung injury

BACKGROUND

Primary blast injuries, specifically lung injuries, resulting from blast overpressure exposures are a major source of mortality for victims of blast events. However, existing pulmonary injury criteria are inappropriate for common exposure environments. This study uses Drosophila melanogaster larvae to develop a simple phenomenological model for human pulmonary injury from primary blast exposure.

METHODS

Drosophila larvae were exposed to blast overpressures generated by a 5.1-cm internal diameter shock tube and their mortality was observed after the exposure. To establish mortality thresholds, a survival analysis was conducted using survival data and peak incident pressures. In addition, a histologic analysis was performed on the larvae to establish the mechanisms of blast injury.

RESULTS

The results of the survival analysis suggest that blast overpressure for 50% Drosophila survival is greater than human threshold lung injury and is similar to human 50% survival levels, in the range of overpressure durations tested (1-5 ms). A "parallel" analysis of the Bass et al. 50% human survival curves indicates that 50% Drosophila survival is equivalent to a human injury resulting in a 69% chance of survival. Histologic analysis of the blast-exposed larvae failed to demonstrate damage to the dorsal trunk of the tracheal system; however, the presence of flocculent material in the larvae body cavities and tracheas suggests tissue damage.

CONCLUSIONS

This study shows that D. melanogaster survival can be correlated with large animal injury models to approximate a human blast lung injury tolerance. Within the range of durations tested, Drosophila larvae may be used as a simple model for blast injury.

Morphological changes of the neural cells after blast injury of spinal cord and neuroprotective effects of sodium beta-aescinate in rabbits

OBJECTIVE

Explosive blast neurotrauma is becoming more and more common not only in the military population but also in civilian life due to the ever-present threat of terrorism and accidents. However, little attention has been offered to the studies associated with blast wave-induced spinal cord injury in the literatures. The purpose of this study is to report a rabbit model of explosive blast injury to the spinal cord, to investigate the histological changes, focusing especially on apoptosis, and to reveal whether beta-aescinate (SA) has the neuroprotective effects against the blast injury.

METHODS

Adult male New Zealand white rabbits were randomly divided into sham group, experimental group and SA group. All rabbits except the sham group were exposed to the detonation, produced by the blast tube containing 0.7 g cyclotrimethylene trinitramine, with the mean peak overpressure of 50.4 MP focused on the dorsal surface of T9-T10 level. After evaluation of the neurologic function, spinal cord of the rabbits was removed at 8 h, 1, 3, 7, 14 or 30 days and the H&E staining, EM examination, DNA gel electrophoresis and TUNEL were progressively performed.

RESULTS

The study demonstrated the occurrence of both necrosis and apoptosis at the lesion site. Moreover, the SA therapy could not only improve the neurologic outcomes (P<0.05) but also reduce the loss of motoneuron and TUNEL-positive rate (P<0.05).

CONCLUSIONS

In the rabbit model of explosive blast injury to the spinal cord, the coexistent apoptotic and necrotic changes in cells was confirmed and the SA had neuroprotective effects to the blast injury of the spinal cord in rabbits. This is the first report in which the histological characteristics and drug treatment of the blast injury to the spinal cord is demonstrated.