34 Con f_l ict surgery

BLAST INJURIES
BLAST
Ballistic injuries
CONSIDERATIONS
Complex dismounted blast injury
DAMAGE CONTROL SURGERY
DECISION MAKING WITHIN THE DEPLOYED ENVIRONMENT
ETHICAL AND LEGAL
Environmental effects
HOW IS WAR SURGERY DIFFERENT
INFECTION
Improvised explosive devices
Introduction
Learning objectives
MANAGEMENT OF GUNSHOT WOUNDS
MASSIVE TRANSFUSION
MEDICAL EVACUATION
MEDICAL SUPPORT ROLES
PRINCIPLES OF WAR SURGERY
Primary blast injury
Quaternary and quinary injury
REFERENCES
SURGERY
Secondary blast injury
Tertiary blast injury
WEAPON EFFECTS Ballistics

BLAST INJURIES

Blast injuries are classiﬁed by the blast mechanism ( Table 34.3 BLAST INJURIES

Blast injuries are classiﬁed by the blast mechanism ( Table 34.3

BLAST

As already discussed, blast has become the predominant mechanism of injury in recent conﬂicts. Unfortunately , terror ist attacks within urban centres mean that these injuries are increasingly encountered within civilian practice. While explosives come in many forms and their e ﬀ ects vary as a result, fundamental principles underlie all blast events. An explosiv e may be deﬁned as ‘a substance that can made to undergo a rapid chemical reaction that will transform a liquid or solid into gas, liberating a large amount of ener The explosive properties of such a material are determined Frederick Gerard Friedlander , 1917–2001, Austrian mathematician, lived and worked in the UK from 1934. at which energy is expelled. Low explosives react by a pro - y the reaction is propagated by cess called deﬂagration, wher eb ﬂame passing through the material at a rate signiﬁcantly slower than the speed of sound. They are made up of a combusti - ble material and an accompanying oxidant. Low explosives include gunpowder, gasoline and pyrotechnics such as ﬁre - works and ﬂares. Low explosives more commonly cause bur ns than typical blast injuries and will not be discussed further. In contrast, high explosives degrade via detonation. Shock - waves are passed through the material at supersonic speeds and the resultant energy is expelled a t very high rates. High explosives include plastic e xplosive and trinitrotoluene (TNT). The input of a relatively small amount of energy results in the production of a very large volume of gas, at high speed and pressure. The outward expansion causes a wave of compressed air that moves away from the point of detonation at supersonic speeds and in a uniform sphere (within a free ﬁeld). The change in surrounding pressure is described as the blast overpressure. Following detonation within a free ﬁeld, there is a near instantaneous pressure rise, which falls expo - nentially . This is classically described by the Friedlander curve ( Figure 34.4 ). This characteristic pressure peak is only seen during a truly free (almost theoretical) scenario. Enclosure of the blast or reﬂection of blast waves b y people, vehicles or buildings is likely to change the overpressure proﬁle such that high pressures may be sustained for longer periods and have a greater propensity to cause injury . For this reason, blasts within enclosed spaces are notable for causing a greater range and severity of injury . In addition to expanding gases, detonation of explosives may result in the expulsion of fragments. These fragments may be part of a device casing, separate material deliberately added with the intention of fragmentation or environmental material ﬂung by the blast. Blast winds are generated by the displacement of surround - ing air. The direction of these winds may change as the blast - - be 21 gy’.

Blast overpressure Quasi-instantaneous pressure rise Pressure Positive pressure phase Negative pressure phase Atmospheric pressure Time Figure 34.4 Theoretical blast overpressure changes within a free /f_i eld.

creates a partial vacuum. BLAST

creates a partial vacuum.

Ballistic injuries

Terminal ballistics (or wound ballistics) describes the interac tion between projectiles and target tissue. This interaction and subsequent transfer of energy cause injury . The kinetic energy of the bullet is related to the mass and velocity of the impacting projectile. Both the mass and velocity of military ﬁrearms may be considerably greater than those commonly seen in civilian trauma, leading to higher energies and more severe wounds. While the weapon and ammunition type may be a determinant in the potential injury caused, many other factors, including range, angle, clothing, armour and anatomical variation, will determine the actual wound pattern. Although an understand ing of ballistic science may allow a surgeon to anticipate possible injuries, each should be evaluated and managed individually . In consideration of the damage done, tissue may be described by the areas of disruption caused by the projectile and the permanent and temporary w ound cavity , which are illustrated in Figure 34.2 . T he permanent cavity is the localised area of deﬁnitive tissue injury caused by contact with the projectile. This area of cell necrosis is the result of direct contact, crushing and laceration of tissues in the path of the projectile. T he size and - trajectory of the projectile determines the cavity size. This type of cavity is the predominant wound e ﬀ ect of pistol bullets, - which have relatively low energy . Higher energy projectiles, including military riﬂe and machine gun bullets, may be subject to greater degrees of deformation and tumbling as they travel through tissue. This increases the e ﬀ ective cross- sectional area of the projectile and may lead to a larger and - less regular permanent wound cavity . In contrast, the temporary wound cavity is created by lat - eral displacement of tissue that has not been in direct contact with the bullet. The degree of damage in this area is depen - dent on the amount of energy transferred by the bullet and the material properties of the tissue itself. Individual tissues have - an elastic strength that resists the stretching caused by a pro - - jectile. As the energy incr eases, the tissue is no longer able to rebound and, above certain thresholds, contusion, laceration and permanent damage may occur. Skin, muscle, lung and bowel wall tissues have good elastic strength and may r ebound well following stretch, with minimal damage within the tem - - porary wound cavity . In contrast, liver, brain and spleen have poor elasticity and are more likely to shatter when stretched. The incompressibility of ﬂuids within hollow organs (bowel and bladder) means that they ar e vulnerable to stretch despite favourable properties of the tissue wall itself. - Summary box 34.2 Ballistics /uni25CF - /uni25CF /uni25CF

A B Figure 34.2 Diagram showing the permanent wound cavity (A) and the temporary wound cavity (B). This relatively large temporary cavity is more typical of a higher energy weapon. Internal ballistics – characterise the projectile within the weapon during /f_i ring External ballistics – characterise the projectile in free /f_l ight Terminal ballistics – characterise the projectile/tissue interaction

Ballistic injuries

CONSIDERATIONS

International Humanitarian Law (IHL) regulates humanitar - ian issues during armed conﬂict. Modern IHL is derived from a variety of sources, notably the Geneva Conventions and their additional protocols, along with further speciﬁc regulations from the United Nations and The Hague Conv entions. IHL provides medical personnel with rights in times of armed war, but also assigns duties to them surrounding the rights of protected personnel under their care. Importantly , medical personnel are bound by medical eth - - ics and IHL to treat patients solely based on need and without regard for their nationality , race and class or their religious or political beliefs. Along with providing medical support to deployed forces, trea tment is o ﬀ ered to both home nation and enemy combat - ants. The treatment of such patients may require a c hange in the approach to their deﬁnitive care. Evacuation of these Medical support roles ) may not be possible and the staged approach to care may need modiﬁcation. Transfer to host nation medical facilities may be possible but dependent on local capability . This scenario may require an adaptation to clinical thinking. As an example, consider the ethical and logistical dilemma in performing revascularisation and orthoplastic procedures for a local patient in a countr y without rehabilita tion facilities. Medical personnel and facilities are protected under IHL and should not be attacked. However, the nature of modern conﬂict is unconventional; guerrilla warfare and the inability of deploy ed forces to deﬁne the enemy combatant requires the security of facilities and personnel to be of the highest priority . CONSIDERATIONS

Complex dismounted blast injury

In contrast, the dismounted IED casualty may sustain a char acteristic pattern of injuries, including lower limb amputation, pelvic fracture and genital, perineal and rectal injuries. The most common cause of death in such casualties is from 26 haemorrhage. Initial management is therefore focused upon control of bleeding with tourniquets and swift proximal vascular control. This group may in the future beneﬁt from the judicious use of resuscitative endovascular balloon occlusion 14,32 of the aorta (REBOA) as a bridge to deﬁnitive control. role of REBOA in civilian trauma remains greatly contested and its use in military and austere settings may be complicated by long timelines entailing a prohibitively high burden of ischaemic injury . Following control of bleeding and DCR, management principles for complex dismounted blast injury include debridement and delayed reconstruction of soft tissues. Orthopaedic considerations include external ﬁxation of pelvic injuries and the r etention of maximal limb length for rehabilitation. High rates of rectal injuries requir e careful rec - tal examination with proctoscopy and early considera tion of faecal diversion. Genitourinary injuries should be managed with careful catheterisation if possible (and consideration of 33 suprapubic catheters) with exploration of scrotal wounds. - Complex dismounted blast injury

DAMAGE CONTROL SURGERY

15 DCS was ﬁrst described by Rotondo et al ., although the idea of an abbreviated laparotomy for the unwell patient was not totally novel. The concepts of DCS were initially applied to complex trauma patients with combined vascular and visceral - injuries. Improved outcomes were seen following DCS princi - ples compared with conventional deﬁnitive surgery . The DCS approach is to restore physiology over anatomy and is typically divided into several phases: /uni25CF Phase 1 . Recognition of injury severity and the need for - damage control principles, both surgical and resuscitative. Features of phase 1 include rapid-sequence induction of anaesthesia and intubation, early rewarming and prompt movement to the operating theatre. /uni25CF Phase 2 . Immediate laparotomy with rapid control of bleeding and contamination, abdominal packing and tem - porary wound closure. /uni25CF Phase 3 . Movement to the intensive care unit (ICU) for ongoing resuscitation with normalisation of biochemical and physiological parameters. /uni25CF Phase 4 . Re-exploration in the operating theatre to per - form deﬁnitive repair of all injuries. Multiple procedures on multiple occasions may be required. Even at this stage, non-essential procedures may be truncated or delay ed if physiology deteriorates. may not be straightforward. While various physiological and biochemical markers of injury have been suggested, there is no validated threshold. Hypothermia, coagulopathy , acidosis, blood loss and anticipated operative time should all be consid ered (see Chapters 26 and 27 ). The beneﬁts of a DCS approach to those patients who need it has been repeatedly shown, but liberal, and perhaps overzealous, use of DCS is unlikely to be beneﬁcial to those who would tolerate deﬁnitive repair. DCS puts a heavy toll on thea tre and ICU resources. In addition, multiple trips to theatre may increase the likelihood of morbidity , including abdominal wall hernias, ﬁstulae and infection. Damage control resuscitation (DCR) should be concur rent with DCS. The principles of DCR include permissive hypotension, the avoidance of crystalloid with haemostatic resuscitation and the recognition and management of acute traumatic coagulopathy (ATC). The applica tion of these prin ciples to military patients is uncertain because of longer time lines. Prolonged periods of permissive hypotension are likely 16 to be harmful, whereas haemostatic resuscitation and man agement of ATC is ine ﬀ ectual in the absence of haemorrhage 17 control. DAMAGE CONTROL SURGERY
15 DCS was ﬁrst described by Rotondo et al ., although the idea of an abbreviated laparotomy for the unwell patient was not totally novel. The concepts of DCS were initially applied to complex trauma patients with combined vascular and visceral - injuries. Improved outcomes were seen following DCS princi - ples compared with conventional deﬁnitive surgery . The DCS approach is to restore physiology over anatomy and is typically divided into several phases: /uni25CF Phase 1 . Recognition of injury severity and the need for - damage control principles, both surgical and resuscitative. Features of phase 1 include rapid-sequence induction of anaesthesia and intubation, early rewarming and prompt movement to the operating theatre. /uni25CF Phase 2 . Immediate laparotomy with rapid control of bleeding and contamination, abdominal packing and tem - porary wound closure. /uni25CF Phase 3 . Movement to the intensive care unit (ICU) for ongoing resuscitation with normalisation of biochemical and physiological parameters. /uni25CF Phase 4 . Re-exploration in the operating theatre to per - form deﬁnitive repair of all injuries. Multiple procedures on multiple occasions may be required. Even at this stage, non-essential procedures may be truncated or delay ed if physiology deteriorates. may not be straightforward. While various physiological and biochemical markers of injury have been suggested, there is no validated threshold. Hypothermia, coagulopathy , acidosis, blood loss and anticipated operative time should all be consid ered (see Chapters 26 and 27 ). The beneﬁts of a DCS approach to those patients who need it has been repeatedly shown, but liberal, and perhaps overzealous, use of DCS is unlikely to be beneﬁcial to those who would tolerate deﬁnitive repair. DCS puts a heavy toll on thea tre and ICU resources. In addition, multiple trips to theatre may increase the likelihood of morbidity , including abdominal wall hernias, ﬁstulae and infection. Damage control resuscitation (DCR) should be concur rent with DCS. The principles of DCR include permissive hypotension, the avoidance of crystalloid with haemostatic resuscitation and the recognition and management of acute traumatic coagulopathy (ATC). The applica tion of these prin ciples to military patients is uncertain because of longer time lines. Prolonged periods of permissive hypotension are likely 16 to be harmful, whereas haemostatic resuscitation and man agement of ATC is ine ﬀ ectual in the absence of haemorrhage 17 control. DAMAGE CONTROL SURGERY
15 DCS was ﬁrst described by Rotondo et al ., although the idea of an abbreviated laparotomy for the unwell patient was not totally novel. The concepts of DCS were initially applied to complex trauma patients with combined vascular and visceral - injuries. Improved outcomes were seen following DCS princi - ples compared with conventional deﬁnitive surgery . The DCS approach is to restore physiology over anatomy and is typically divided into several phases: /uni25CF Phase 1 . Recognition of injury severity and the need for - damage control principles, both surgical and resuscitative. Features of phase 1 include rapid-sequence induction of anaesthesia and intubation, early rewarming and prompt movement to the operating theatre. /uni25CF Phase 2 . Immediate laparotomy with rapid control of bleeding and contamination, abdominal packing and tem - porary wound closure. /uni25CF Phase 3 . Movement to the intensive care unit (ICU) for ongoing resuscitation with normalisation of biochemical and physiological parameters. /uni25CF Phase 4 . Re-exploration in the operating theatre to per - form deﬁnitive repair of all injuries. Multiple procedures on multiple occasions may be required. Even at this stage, non-essential procedures may be truncated or delay ed if physiology deteriorates. may not be straightforward. While various physiological and biochemical markers of injury have been suggested, there is no validated threshold. Hypothermia, coagulopathy , acidosis, blood loss and anticipated operative time should all be consid ered (see Chapters 26 and 27 ). The beneﬁts of a DCS approach to those patients who need it has been repeatedly shown, but liberal, and perhaps overzealous, use of DCS is unlikely to be beneﬁcial to those who would tolerate deﬁnitive repair. DCS puts a heavy toll on thea tre and ICU resources. In addition, multiple trips to theatre may increase the likelihood of morbidity , including abdominal wall hernias, ﬁstulae and infection. Damage control resuscitation (DCR) should be concur rent with DCS. The principles of DCR include permissive hypotension, the avoidance of crystalloid with haemostatic resuscitation and the recognition and management of acute traumatic coagulopathy (ATC). The applica tion of these prin ciples to military patients is uncertain because of longer time lines. Prolonged periods of permissive hypotension are likely 16 to be harmful, whereas haemostatic resuscitation and man agement of ATC is ine ﬀ ectual in the absence of haemorrhage 17 control.

DECISION MAKING WITHIN THE DEPLOYED ENVIRONMENT

The damage control approach is vital in a proportion of war injuries, but thought must be given to available resources. Within a well-established role 3 unit, both DCS and deﬁnitive procedures are likely to be possible. Blood and blood products are also likely to be available and restocked regularly . In this mode of care. In contrast, decision making becomes more crucial within the austere environment. Theatre space, intensive care beds, - equipment and blood products may be limited. Long e vacua - tion times may contraindicate per missive hypotension. Limited resources, such as blood, may need to be divided among casualties. Within a role 1 or role 2 facility , immediate evacuation may be undertaken in preference to more thorough stabilisation. Decision making of this na ture is complex and di ﬃ cult and requires practice in the context of simulation, exercises and courses. - DECISION MAKING WITHIN THE DEPLOYED ENVIRONMENT

ETHICAL AND LEGAL

ETHICAL AND LEGAL
ETHICAL AND LEGAL

Environmental effects

As already alluded to, the shockwave of blast overpressure is modiﬁed by an enclosed or partially enclosed space. Envi ronmental variations may make marked di ﬀ erences to injury rates and clinical presentations following blast. Higher rates of blast lung and TM rupture are seen following enclosed blast (in which both the casualty and b last are enclosed). In contrast, secondary blast injuries may be lower in number as more people are protected from energised fragments. Tertiary injury is di ﬃ cult to predict based on blast characteristics but a higher proportion of blunt injuries have been seen following enclosed blast. A distinct pattern of injury has been described following underbody blast against military vehicles. Underbody blast casualties have a greater range of injuries and are overall more 26 se verely injured. In addition to blunt injury sustained from displacement within the vehicle, the e ﬀ ect of blast is mani fested by propagation of the shockwave through a solid, with both upwards deformation of the ﬂoor and a rapid upwards acceleration of the whole vehicle and subsequent decelera tion following impact with the ground. The solid b last injury 27 burden includes severe foot and ankle and pelvic injuries. Mortality from underbody blast is most commonly caused by head injury and non-compressible torso haemorrhage, includ 29 ing aortic disruption and liver laceration. Environmental effects

HOW IS WAR SURGERY DIFFERENT

HOW IS WAR SURGERY DIFFERENT?

While civilian trauma surgery bears some of the hallmarks of the battleﬁeld, there are fundamental contrasts in environment and injury pattern that must be appreciated: /uni25CF The environment of war is likely to be austere. While recent long-term deployment has led to the establishment of some well-equipped ﬁeld hospitals, logistical and per sonnel restrictions mean that sophisticated diagnostic and therapeutic techniques may not be available. /uni25CF War is hostile and potentially dangerous. Necessary workforce protection must be considered to ensure the safety of medical personnel and patients alike. Modern ﬁghting forces employ physician-led resuscitation, along The papyrus is named after Edwin Smith, the Egyptologist who discovered it in 1866; it is held at the New Y ork Academy of Medicine, NY , USA. Dominique Jean Larrey , 1766–1842, French surgeon in Napoleon’s Grand Armée. with forward surgical teams. Moving medical personnel closer to the ﬁghting may increase their personal risk. /uni25CF War injuries are di ﬀ erent from civilian trauma. Modern weapons may deliver such amounts of energy that the tis - sue destruction and patterns of injury seen are unlike all but the most extreme of civilian trauma. and /uni25CF War is a mass casualty situation. Although casualty num - 1 bers vary between treatment facilities, triage is an import - ant aspect of military surgery . The dictum ‘do the best for the most, not everything for everyone’ is important and may require a change in thinking for many used to civilian practice. - /uni25CF War surgery is usually delivered in stages. The principles of damage control are often applied to allow transfer of patients between echelons of care. Careful planning, coor - dination and communication are essential. -

Principles of war surgical management • Blast and ballistic injury • BCE )

HOW IS WAR SURGERY DIFFERENT?

Principles of war surgical management • Blast and ballistic injury • BCE )

HOW IS WAR SURGERY DIFFERENT?

Principles of war surgical management • Blast and ballistic injury • BCE )

INFECTION

Battleﬁeld wounds are by their very nature grossly contami - nated and the treatment and prevention of infection is one of the basic functions of war surgery . Wounds sustained during warfare are high-energy wounds with large areas of devitalised tissue. This is particularly the case for dismounted b last injuries - where there is massive disruption of tissue planes with soil and debris forced into the zones of injury ( Figure 34.6 ). Wounding agents are all non-sterile and highly likely to be contaminated by bacteria. Both large-calibre ballistic wounds and blast wounds may contain dirty clothing or contaminated fragments. Multiple steps in casualty ev acuation and substan - tial delays before treatment may allow progression of contam - ination to clinically signiﬁcant infection. Speciﬁc organism patterns will depend on endemic ﬂora, but commonly seen bacteria include: /uni25CF Gram-positive cocci, including staphylococci, streptococci and enterococci; /uni25CF Gram-negative rods, including Escherichia coli , Proteus and Klebsiella ; - /uni25CF Pseudomonas , Enterobacter , Acinetobacter and Serratia are common nosocomial pathogens that are usually expected among casualties following long periods of hospitalisation; - /uni25CF Salmonella , Shigella and Vibrio should be suspected in cases of bacterial dysentery . 28 Fungal infection, including Candida , should be considered - in casualties hospitalised for prolonged periods, those who are malnourished or immunosuppressed or those who have received broad-spectrum antibiotics, adrenocortical steroids or parenteral nutrition. Techniques to reduce the infectious burden are part of - every aspect of war surgery . At the point of wounding, sterile dressings should be applied. Antibiotics, if available, should be 30,31 administered if evacuation and further treatment are likely to be delayed. Empirical antibiotic therapy should be commenced or con - tinued following movement to a medical facility . The mainstay of treatment is prompt surgical control of the infectious cause with adequate debridement of non-viable tissue and drainage The of infective material. Extensive irrigation should be employ ed to remove dead tissue and foreign bodies. High-pressure wound lavage has been shown to increase bacterial propagation into soft tissue and is not indicated. With few exceptions (such as facial wounds), closure of con - taminated war wounds should not be performed at the time of ﬁrst operation. The open wound should be left with clean, moist dressings. Negative pressure wound therapy should be considered for larger wounds. Antibiotic therapy should be tailored to speciﬁc wounds with the empirical antibiotic choice dependent on the injured body region or cavity . Microbial culture will aid the guidance wounds should be considered tetanus prone and appropriate tetanus prophylaxis administered. Clinical experience and judgement are essential in the assessment of war wounds. Adequate exposure, often with extension of the wound, is mandated to ensure debridement of all devitalised tissue. Serial operations may be r equired. Early consideration should be given to soft-tissue coverage. The skin is often remarkably resilient to injury and conservative debride - ment of it may facilitate more successful reconstruction.

(b) (c) Figure 34.6 Blast injuries including bilateral lower limb amputation (a) , buttock and thigh soft tissue injury (b) and complex hind foot injury (c) . The need for extensive debridement is evident from the level of wound contamination and non-viable tissue.

INFECTION

Improvised explosive devices

The characteristic weapon of modern warfare has been the IED, which was the leading cause of death among coalition 22 troops during conﬂicts in Iraq and Afghanistan. devices may range from rudimentary homemade explosives to sophisticated devices containing high explosives. Within this broad range of devices are further categories including road side explosives and blast mines, suicide bombers and explosive formed projectiles (EFPs). EFPs are a particular form of device with a deformable plate on the uppermost surface. The deto nation of the de vice and expansion of the explosive products deforms this plate into a missile shape, while simultaneously accelerating it upwards to very high velocities. Alternatively , copper plates ma y melt to create a high-speed molten jet (a shaped charge). Upon contact with a target (typically a vehi cle), the missile impacts the hull of the vehicle with a degree of penetration dependent on the device and vehicle armour. Huge amounts of kinetic energy are dispersed through the vehicle and occupants. Injuries may be caused by both direct impact of the deforming hull and gross upwards acceleration followed by downwards deceleration of the whole vehicle. Improvised explosive devices

Introduction

INTRODUCTION

The treatment of war wounds is as ancient as warfare itself. The Edwin Smith papyrus has been dated to 1600 /uni00A0 /b.sc/c.sc/e.sc is the oldest known treatise on trauma surgery and anatomy . The history of battleﬁeld surgery is the history of surgical advancement and the importance of the medical lessons learned from war have long been recognised. While almost every conﬂict has served to increase our knowledge of the treatment of war injuries, and many indi viduals have played signiﬁcant parts in the development of war surgery , Dominque Jean Larrey is considered by many to be the ﬁrst modern military surgeon. Larrey , a French battleﬁeld surgeon and favourite of Napoleon, devised some of the ﬁrst systems of triage and casualty care that still form the funda mentals of modern military medicine. These systems must be in place in order to overcome the di ﬃ culties and logistical chal lenges of providing medical care to a battleﬁeld.

He who wishes to be a surgeon must /f_i rst go to war. Hippocrates ( c .460–377 /uni00A0

Learning objectives

To understand and appreciate: Fundamental differences of war surgery • Injury patterns of modern warfare • Learning objectives

To understand and appreciate: Fundamental differences of war surgery • Injury patterns of modern warfare •

MANAGEMENT OF GUNSHOT WOUNDS

The management of gunshot wounds in a conﬂict setting may - di ﬀ er from that in civilian practice. The typical low-energy wounds caused by pistols are sometimes managed conserva - tively in civilian trauma centres with adequate wound care, cleaning and antibiotics. Military wounds are associated with higher energies, higher rates of infection and more sev ere injury . The extent of these injuries, including the size of the wound cavities, may not be adequately assessed without thorough surgical examination ( Figure 34.3 ). As such, most penetrating wounds in the military setting are explored under anaesthetic. The extent and capacity for recovery of the temporary wound cavity may not be appreciated at the time of the ﬁrst oper ation. A damage control approach should be adopted if the physiology of the patient dictates it. An interval period may also allow for adequate appreciation of the permanent wound cavity , along with the r esponse of the surrounding structures and demarcation of non-viable tissue.

(b) Figure 34.3 Entry wound to the right shoulder (a) with the wound extended in order to assess it adequately (b) .

MANAGEMENT OF GUNSHOT WOUNDS

(b) Figure 34.3 Entry wound to the right shoulder (a) with the wound extended in order to assess it adequately (b) .

MANAGEMENT OF GUNSHOT WOUNDS

(b) Figure 34.3 Entry wound to the right shoulder (a) with the wound extended in order to assess it adequately (b) .

MASSIVE TRANSFUSION

While haemorrhage control prior to the need for massive transfusion is ideal, this is often not the case. The degree of injury and associated massive blood loss associated with war injuries may necessitate large-volume transfusion. The use of crystalloids to resuscitate exsanguinating patients is strongly discouraged, but the optimal ratio of blood products has not yet been ascertained. Massive transfusion protocols exist within most deployed units. The use of such a protocol in a UK role 3 facility , along with aggressive resuscitation and use of blood products, has been associated with improved trauma 18 outcomes. The success of such a protocol is highly dependent on a steady stream of blood products and reﬂects the sophis ticated transfusion infrastructure that should be woven into a deployed capability . Blood transfusion is increasingly administered in a more forward location (within both role 1 and role 2 environments) with limited volumes of blood transported to the point of w ounding by aeromedical response teams. Future resuscitativ strategies are under much scrutiny . The use of whole blood (and the possibility of ‘walking blood banks’) may be combined with alternatives to conventional blood components, which can join adequate oxygen carriage with positive or neutral e ﬀ ects 19 on patient coagulation. MASSIVE TRANSFUSION

MEDICAL EVACUATION

Medical evacuation refers to the movement and en route care of casualties within a conﬂict zone. The evacuation may be the initial movement from a battleﬁeld or between other more sophisticated echelons of care, up to and including repatriation to a home nation. Aeromedical evacuation using either ﬁxed or rotary wing - aircraft has had a major impact on evacuation timelines. Certain considerations must be made prior to and during aeromedical evacuation: /uni25CF the patient should be su ﬃ ciently stabilised for the antici - pated mode and duration of travel; /uni25CF the patient’s airway and breathing are adequate for move - ment; /uni25CF intravenous access, surgical drains, urinary catheters and any other tubes should be ﬁrmly secured; - /uni25CF patients at high risk for thoracic barotrauma should be considered for prophylactic chest tube placement before prolonged aeromedical evacuation; - /uni25CF blankets and/or warmers should cover the patient securely to mitigate against hypothermia. The capability of di ﬀ erent evacuation platforms may vary ac - from highly sophisticated mobile critical care units to the simple transportation of casualties by non-medical personnel. These capabilities, along with the timelines and distances involved in casualty movement, should be major considerations for the planning of medical support operations. The ‘golden hour’ is an oft-quoted principle in trauma medicine and refers to the initial time period following injury during which a life is most likely lost or saved. Although the ori - 3 gins and applicability of the term are disputed, the principle is ubiquitously understood. Within the military setting, death is certainly seen to occur most commonly within the prehospital environment and within a short period after injury , with better 4 outcomes seen after rapid transport to surgical care. Improvement in outcomes from severe deployed trauma may rely upon either the shortening of time to damage con - trol care or lengthening of the ‘golden hour’. Shortening of timelines may be achieved with change in transport systems or deployment of surgical teams further ‘forward’, or even the use of telemedical technology to utilise remote expertise. Length - ening of the golden hour may perhaps be achieved by the use of novel prehospital haemorrhage control techniques or an 5–8 increase in the availability of pr ehospital blood products. MEDICAL EVACUATION

MEDICAL SUPPORT ROLES

The term ‘role’ is used to designate the tiers of medical support 2 that integrate into a modern military operation. An apprecia tion of the capabilities and limitations of these roles is essential to improving the care of casualties at each stage. Di ﬀ erent nations and forces will have medical support conﬁgured with some variability but, ov erall, systems are similar in order to ensure that the basic treatment, supply and evacuation needs that are essential for a military operation are available. /uni25CF Role 1 medical support provides for routine primary health care, specialised ﬁrst aid, triage, resuscitation and stabilisation. It is integrated within a small unit. The capa bilities of role 1 care will depend greatly on the size of the unit and the training of the personnel within it. /uni25CF Role 2 provides an intermediate capability for the re ception and triage of casualties, as well as being able to perform resuscitation and treatment of shock to a higher technical level than role 1. It is prepared to provide ev uation from role 1 facilities. It has capability for damage control surgery (DCS) and may include a limited holding facility for the short-term holding of casualties until they can return to duty or be evacuated. /uni25CF Role 3 medical support is deployed hospital care and the elements required to support it. This includes a mission- tailored variety of clinical specialties, including primary surgery and diagnostic support. In recent conﬂicts role 3 facilities grew and evolved into sophisticated hard-built hospitals. Summary box 34.1 Medical support roles /uni25CF /uni25CF /uni25CF /uni25CF care that cannot be deployed to the area of operations or is too time-consuming to be conducted there. It is normally provided in the country of origin or an allied nation de - pending on the location of deployment and time-lines of transfer. It is important to appreciate that these roles are highly vari - able both within and between di ﬀ erent nations. The size and - scale of the operations as a w hole, along with predictions of both civilian and military medical requirements, will dictate the structure of the medical support.

R1– unit-level medical care including /f_i rst aid and primary health care R2 – intermediate unit for resuscitation, damage control and stabilisation R3 – deployed hospital care with multispecialty capability R4 – de /f_i nitive hospital care within the home or allied nation

MEDICAL SUPPORT ROLES

PRINCIPLES OF WAR SURGERY

Battleﬁeld death occurs early (or immediately) because of devastating central nervous system injury and haemorrhage, or - - - late because of infection. Some of the injuries causing imme - diate death (including brain, heart and great vessel injury) are 11 non-survivable and may only be managed with prevention. Treatment of haemorrhage is therefore the mainstay of military trauma medicine. Bleeding should be recognised 12 and managed from the point of wounding. Tourniquets are indicated for the control of catastrophic extremity bleeding. Non-compressible torso haemorrhage carries a poor progno - 13 sis, although it may be amenable to methods of endovascular 14 control not yet commonly used. A damage control approach to surgery must be employed to stop bleeding, to remove necrotic tissue and foreign material and to reduce contamination. In addition to life-saving sur - gery , procedures to salvage limbs, including revascularisation 10 (or temporary shunting) and fasciotomy , should be considered early , when physiology allows.

gunshot wounds and explosions among US personnel. Gunshot (% of total Explosion (% of injuries) total injuries) US Civil War 91 9 First World War 65 35 Second World War 27 73 Korean War 31 69 Vietnamese War 35 65 Iraq/Afghanistan War 19 81 10 Adapted from Owens et al .

PRINCIPLES OF WAR SURGERY

Primary blast injury

Primary blast injuries result from the overpressure and are, as such, unique to blast. The e ﬀ ect of blast overpressure is most marked at the interface between air and tissue or liquid. Tympanic membrane (TM) rupture is the most common primary blast injury . Patients may be asymptomatic or have a degree of transient hearing loss and otorrhoea. Previously , the presence of TM rupture was used as a marker for other occult blast injuries. This has been challenged recently by ﬁndings that show TM injury is not ubiquitous in the presence of more severe primary blast injury . The blast environment and orien tation of the ear canal to the shockwave are likely to determine the chance of injury . researched blast phenomenon. The exact mechanism of blast lung remains contested but it depends on the propagation of energy from the shockwave into the lung tissue, where it causes disruption. Proposed mechanisms of injury include spalling (disruption of tissues at air–liquid interfaces), implosion (com - pression and re-expansion of air-ﬁlled structures) and rapid These acceleration of tissues of di ﬀ erent densities. Large animal models have demonstrated that the level of injury is related to the rate of c hest wall displacement, rather than the maximal 23 - depth of deﬂection. The severity of injury is dependent on the strength of the blast, the range from detonation and the surrounding environment. - Those working closely with explosives may wear personal armour that assists in decoupling the e ﬀ ect of the primary blast. Current examples of such armour tend to be cumber - some. More common varieties of torso body armour pr ovide protection against penetrating injury but probably do little to - mitigate the e ﬀ ects of primary blast. The pathophysiolog y of blast lung includes both immedi - ate and delayed responses. There is an immediate bradycardia and apnoea of variable length, which is likely to be a vagally 24 mediated reﬂex. The lung injury itself is typiﬁed by alveo - lar capillary rupture with subsequent intrapulmonary bleed - ing and oedema. The extent of this injury is proportional to the blast exposure and may range from microscopic petechial injury to areas of frank haemor rhage. While rarely seen in isolation, primary blast may leave lit - ). tle external evidence of injury since the skin itself is rarely a ﬀ ected. Clinical features of blast lung include progressive hypoxia, which may not be apparent at the time of injury and is rela ted to the inﬂammatory response to intrapulmonary hae - morrhage and worsening oedema. Other structural lung injuries are associated with primary blast, although the prediction of these injuries by blast conditions is not consistent and is likely to be complicated by tertiary impact. Pneumothoraces may occur as a result of pleural rupture in the absence of penetrating injury . Injury to the larger vessels ma y lead to haemothoraces and the formation of alveolar–venous or bronchovenous ﬁstulae. Air embolism due to such ﬁstulae may cause acute hypoxia with - cardiovascular collapse and is a leading cause of death in those who do not survive until treatment. The diagnosis of blast lung is clinical with ﬁndings of hypoxia following blast exposure. Typical ‘bat-wing’ pulmo - nary inﬁltra tes are seen on the chest radiograph and computed tomography may discriminate these injuries from the more peripheral contusions seen in blunt trauma. Imaging may be useful in detecting associated structural lung injuries. T reatment of blast lung is largely supportive. Mechani - cal ventilation may be required but consideration should be given to the possibility of air embolism and pneumothorax that may be exacerbated. Some centres advocate the use of prophylactic bilateral pleural decompression, although ther e is little evidence to suggest an e ﬀ ect on outcomes. Patients with signiﬁcant blast lung injury are highly likely to have sustained other blast-related injuries and any management plan should consider their overall condition.

TABLE 34.3 Classi /f_i cation of blast injuries. Classi /f_i cation Injury type Examples Primary blast Overpressure Tympanic membrane injury, blast lung, intestinal blast injury Secondary blast Penetrating/ All penetrating injuries fragmentation Tertiary blast Blunt Blunt and crush injuries, traumatic amputation Quaternary blast Miscellaneous Burns, inhalation injury Quinary blast Effect of device Radiation sickness, additions infection

incidence of abdominal injury due to air blast has not been extensively examined, although a recent review of multiple incidents, including a variety of blast conditions, showed that abdominal injury is not common – seen in around 3% of inci 25 dents. Damage is dependent on coupling of the blast overpressure and the shockwave to a stress wave that travels through the abdomen. The e ﬀ ect of shockwave dispersal is most marked at tissue–air interfaces. As such, the hollow organs are those most commonly injured. The caecum is probably most sensi tive to intestinal blast injury . Conversely , the small bowel and its extensive mesentery may be more susceptible to large shear waves causing mesenteric tearing. The presentation of primary blast injury to the bow el may be delayed relative to the acute onset of blast lung. Abdomi nal symptoms may be absent initially with progression to pain and frank peritonitis, should perforation and contamination occur. Given the lack of external injury , indications for opera tive intervention are largely clinical, as with conventional blunt abdominal trauma. The patient should be assessed anaesthet ically with particular consideration to the e ﬀ ect of anaesthesia and ventilation on any concomitant blast lung injury . The most common operative ﬁnding of intestinal blast 25 is subserosal haemorrhage. Tearing of the mucosal surface with bleeding into the lumen of the tract may occur following repeated exposure to relatively lower blast overpressures. As in blunt injury , there is a propensity for mural haematomas to progress to perforation as a result of tissue necrosis. Full- thickness injuries to the bowel with immediate perforation can occur with a greater exposure to blast overpressure. The surgical management of blast bowel injury is that of any penetrating and blunt trauma, with primary repair or resection as indicated. Surgical judgement is essential regarding the ﬁnd ings of non-perforated but contused bowel. A damage control approach to such injuries may allow for repeat assessment later, but in a physiologically well patient, in whom a relook would not be justiﬁed, the surgeon must decide to resect a segment or risk future progression of these lesions to perforation. The solid organs are more resistant to primary blast. Paren chymal disruption due to the shockwave has been described at very high levels of overpressure, although the experimental data for these injuries are sparse. Injury , with subsequent bleed ing, may result from rapid distractions of organ attachments and mesenteries. These blast conditions are more likely to be encountered in enclosed conditions and di ﬀ erentiation of pri mary from tertiary injuries is di ﬃ cult. Primary blast injury

Quaternary and quinary injury

Quaternary blast injury refers to a miscellaneous group of injuries that do not fall within other categories. These include burns, inhalational injuries and late-onset respiratory prob lems. Quinary injury refers to injury caused by the intentional addition of either biologically or radioactively active material to an explosive device. Quaternary and quinary injury

REFERENCES

1 Atta HM. Edwin Smith Surgical Papyrus: the oldest known surgi - cal treatise. Am Surg 1999; 65 (12): 1190–2. 2 North Atlantic Treaty Organization. NATO logistics handbook . Brus - sels: NATO Headquarters, 2012. Available from https://www .nato. int/docu/logi-en/logistics_hndbk_2012-en.pdf. 3 Lerner EB, Moscati RM. The golden hour: scientiﬁc fact or medi - cal ‘urban legend’? Acad Emerg Med 2001; 8 (7): 758–60. 4 Howard JT , Kotwal RS, Santos-Lazada AR et al . Reexamination of a battleﬁeld trauma golden hour policy . J Trauma Acute Care Surg 2018; 84 (1): 11–18. 5 Fisher AD, Teeter WA, Cordova CB et al . The role I resuscitation team and resuscitative endovascular balloon occlusion of the aorta. J Spec Oper Med 2017; 17 (2): 65–73. 6 Russo RM, Williams TK, Grayson JK et al . Extending the gold - en hour: partial resuscitative endovascular balloon occlusion of the aorta in a highly lethal swine liver injury model. J Trauma Acute Care Surg 2016; 80 (3): 372–80. 7 Benavides LC, Smith IM, Benavides JM et al . Deployed skills train - ing for whole blood collection by a special operations expedition - ary surgical team. J Trauma Acute Care Surg 2017; 82 (6S Suppl 1): S96–102. 8 Nettesheim N, Powell D, Vasios W et al . Telemedical support for military medicine. Mil Med 2018; 183 (11–12): e462–70. 9 Champion HR, Bellamy RF , Roberts CP , Leppaniemi A. A proﬁle of combat injury . J Trauma 2003; 54 (5 Suppl): S13–19. 10 Owens BD, Kragh JF , Wenke JC et al . Combat wounds in opera - tion Iraqi Freedom and Operation Enduring Freedom. J Trauma 2008; 64 (2): 295–9. 11 Eastridge BJ, Hardin M, Cantrell J et al . Died of wounds on the battleﬁeld: causation and implications for improving combat casu - alty care. J Trauma 2011; 71 : S4–8. 12 Hodgetts TJ. ABC to <C>ABC: redeﬁning the military trauma paradigm. Emerg Med J 2006; 23 (10): 745–6. 13 Morrison JJ, Stannard A, Rasmussen TE et al . Injury pattern and mortality of noncompressible torso hemorrhage in UK combat ca - sualties. J Trauma Acute Care Surg 2013; 75 (2 Suppl 2): S263–8. 14 Morrison JJ, Ross JD, Rasmussen TE et al . Resuscitative endovas - cular balloon occlusion of the aorta: a gap analysis of severely in - jured UK combat casualties. Shock 2014; 41 (5): 388–93. 15 Rotondo M, Schwab C. ‘Damage control’: an approach for im - proved survival in exsanguinating penetrating abdominal injury . J Trauma 1993; 35 (3): 375–82. 16 Garner J, Watts S, Parry C et al . Prolonged permissive hypotensive resuscitation is associated with poor outcome in primary blast inju - ry with controlled hemorrhage. Ann Surg 2010; 251 (6): 1131–9. 17 Khan S, Brohi K, Chana M et al . Hemostatic resuscitation is nei - ther hemostatic nor resuscitative in trauma hemorrhage. J Trauma Acute Care Surg 2014; 76 (3): 561–7; discussion 567–8. 18 Jansen JO, Morrison JJ, Midwinter MJ, Doughty H. Changes in blood transfusion practices in the UK role 3 medical treatment fa - cility in Afghanistan, 2008-2011. Transfus Med 2014; 24 (3): 154– 61. 19 Naumann DN, Khan MA, Smith JE et al . Future strategies for J /uni00A0 Trauma Acute Care Surg 2019; 86 : 163–6. 20 Breeze J, Penn-Barwell J, Keene D et al (eds). Ballistic trauma: a practical guide , 4th edn. Cham, Switzerland: Springer, 2017. 21 Stuhmiller J, Phillips Y , Richmond DR. The physics and mecha nisms of primary blast injury . In: Bellamy RF , Zajtchuk R (eds). Conventional warfare: ballistic, blast and burn injuries . Washington, DC: Department of the Army , O ﬃ ce of the Surgeon General, 1991: 241–70. 22 Ramasamy A, Hill AM, Clasper JC. Improvised explosive devices: pathophysiology , injury proﬁles and current medical management. J R Army Med Corps 2009; 155 (4): 265–72. 23 Cooper GJ, Taylor DE. Biophysics of impact injury to the chest and abdomen. J R Army Med Corps 1989; 135 (2): 58–67. 24 Guy RJ, Kirkman E, Watkins PE, Cooper GJ. Physiologic respons es to primary blast. J Trauma 1998; 45 (6): 983–7. 25 Owers C, Morgan JL, Garner JP . Abdominal trauma in primary blast injury . Br J Surg 2011; 98 (2): 168–79. 26 Singleton JA, Gibb IE, Hunt NC et al . Identifying future ‘unex pected’ survivors: a retrospective cohort study of fatal injury pat terns in victims of improvised explosive devices. BMJ Open 3 (8): e003130. patterns: a forensic biomechanical approach. J R Soc Interface 2011; 8 (58): 689–98. 28 Webster C, Masouros S, Gibb I, Clasper JC. Fracture patterns in pelvic blast injury: a retrospective analysis and implications for fu - - ture preventative strategies. Bone Joint J 2015; 97-B (Suppl 8): 14. 29 Pearce AP , Bull AMJ, Clasper JC. Mediastinal injury is the stron - gest predictor of mortality in mounted blast amongst UK deployed forces. Injury 2017; 48 (9): 1900–5. 30 Cannon JW , Hofmann LJ, Glasgow SC et al . Dismounted complex blast injuries: a comprehensive review of the modern combat ex - perience. J Am Coll Surg 2016; 223 (4): 652–64. 31 Smith S, Devine M, Taddeo J, McAlister VC. Injury proﬁle suf - fered by targets of antipersonnel improvised explosive devices: pro - spective cohort study . - BMJ Open 2017; 7 (7): e014697. 32 Rees P , Waller B, Buckley AM et al . REBOA at Role 2 Aﬂoat: re - suscitative endovascular balloon occlusion of the aorta as a bridge to damage control surgery in the military maritime setting. J R Army Med Corps - 2018; 164 (2): 72–6. - 33 Sharma DM, Webster CE, Kirkman-Brown J et al . Blast injury to the perineum. 2013; BMJ Mil Health 2013; 159 : i1-i3. REFERENCES

SURGERY

Modern warfare has changed over recent decades. The causes of injury are particular to the individual conﬂict, nation and 9 armed service. Historically , penetrating trauma was predom inantly sustained by combat infantry , whereas naval and air personnel sustained more blunt injuries ( Table 34.1 ). Improvements in trauma scoring systems and the develop ment of a concise system for the recording of injuries and casu alty car e have increased the ability of modern armed services to analyse the injury patterns of their deployed personnel. A cohort analysis of combat injuries incurred by US forces showed signiﬁcant di ﬀ erences in injury patterns sustained in the most recent Afghanistan and Iraq conﬂicts compared with those sustained in the Second World War and the Korean and Vietnamese Wars. Head and neck injuries were far more com mon in recent conﬂict whereas thoracic and extremity injuries were less so. This is probably because of the increased use of body armour and similar personnel protective equipment in more recent conﬂicts. The mechanism of injury has also changed. Although bal listic injuries remain an important contributor to battleﬁeld trauma, injuries due to explosions (which include improvised explosive devices [IEDs], landmines, mortars, grenades and rockets) have become incr easingly common and are now the predominant mode of wounding and fatality . The relative pro portions of injuries caused by explosive and ballistic weapons are shown in Table 34.2 . The emergence of explosive patterns of injury is due to the increasing use of IEDs within conﬂicts. IEDs have been the signature weapon within operations in Afghanistan and Iraq; however, their use has not been limited to these regions. The rela tive low cost, ease of production and widespread expertise means that IEDs are likely to play signiﬁcant roles in most contemporary and future conﬂicts.

TABLE 34.1 Historical causes of injury among US service personnel. Service Mechanism Infantry Armoured Sea (%) Air (%) (%) (%) Ballistic 90 50 25 5 Blunt 2–3 5 10 50 Blast 2–3 5 10 <10 Thermal 2–3 25 30 25 Combined <5 15 25 10 9 Adapted from Champion et al .

SURGERY

Secondary blast injury

Secondary blast injury refers to the e ﬀ ect of fragments that are accelerated away from the device following detonation. Sources of fragments include: /uni25CF the casing of the device; /uni25CF purposefully placed fragments within the device; these may include nails, bolts or ball bearings and are embedded within the device or adherent to the exterior; /uni25CF nearby objects including glass and stones; - - - - - /uni25CF biological material including bone may be expelled, par - ticularly following a suicide bomb or antipersonnel mine attack. Shrapnel is often used to describe explosive fragments, although the term is more strictly applied to a speciﬁc form of artillery shell. The energ y of a primary blast wave disperses quickly in proportion to the distance from the blast; it is subject to the inverse cube law . As such, only those within a reasonably small radius of the blast are a ﬀ ected. Conversely , the velocity and w ounding potential of an energised fragment are subject to the inverse square law . Secondary blast injuries may occur at long range from the detonation. Fragments may be accelerated up - to very high velocities. As with ballistics, injuries are dependent on the range and energy of the fragment. In contrast to bullet wounds, the variability of fragments produces a wide range of wounds and no two wounds will be the same ( Figure 34.5 ). The irregular surfaces of fragments cause complex patterns of yaw and tumb le. Both permanent - and temporary wound cavities may be unpredictable and irregular. The management of fragment wounds is similar to ballis - - tic and conventional penetrating trauma. Wounds should be adequately debrided. Fragment wounds should be considered dirty and principles of septic surgery applied. Where possi - - ble, serial debridement and delayed primary closure should be attempted. The fragments should be remo ved at the time of surgery if easily accessible. Other indications for early remov al include fragments within joint spaces or adjacent to structures with danger of erosion and further injuries. Late indications for fragment remo val include ongoing sepsis, pain or lack of func - tion.

Large anterior fragmentation injury. Figure 34.5

Secondary blast injury

Large anterior fragmentation injury. Figure 34.5

Secondary blast injury

Large anterior fragmentation injury. Figure 34.5

Tertiary blast injury

Tertiary blast injury is the result of gross movement of person - nel, objects or infrastructure by blast wind. Tertiary injury is variety of injuries to all organ systems. Traumatic amputation is typically included within this category , although primary blast and the shattering or ‘brisance’ e ﬀ ect on bone may play a part. Tertiary blast injury

WEAPON EFFECTS Ballistics

- The ability to manage conﬂict injuries relies on an under - standing of the underlying mechanism of wounding, which - is likely to be di ﬀ erent from that in civilian trauma. As stated, while ballistic injuries are no longer the most common cause of battleﬁeld injur y , ﬁrearms remain a common element in all conﬂict. Civilian trauma practice, depending on local ﬁrearm laws, may well encompass a signiﬁcant volume of gunshot wounds, although patterns of injury with war wounds may well di ﬀ er as a result of the weapons used. An understanding of the mechanism of ballistic wounding is required to treat these wounds e ﬀ ectively . The earliest recorded depiction of a ﬁrearm is from 1326, but ﬁrearms became ubiquitous on the battleﬁeld during the 20 seventeenth century . Ballistic weapons all work with the same principles – an explosion is used to propel a projectile along and out of a straight tube – but have evolved considerably from rudimentary cannons to sophisticated modern-day ﬁrearms. The explosive force within a modern ﬁrearm comes from pro - pellant encased within a cartridge. The basic design of a car - tridge is shown in Figure 34.1 . - Internal ballistics describes the characteristics of a projec - tile while inside the weapon. The hammer mechanism strikes a primer at the base of the cartridge, which ignites the propel - lant. Hot gas produced by the explosion expands and forces the bullet away from the cartridge and along the bar rel. Spiral grooves, or riﬂing, impart spin on the bullet, which aids accu - e racy and stabilisation.

Bullet Propellant Casing Primer Figure 34.1 Diagram of basic cartridge structure.

advances in ﬁrearm design have served predominantly to improve accuracy , reliability and rate of ﬁre. Ammunition is normally held within a magazine or belt that loads directly into the chamber of the weapon. The loading mechanism determines the rate of ﬁre. In a semiautomatic or fully auto matic system, the recoil forces of the spent cartridge eject the cartridge while resetting the chamber and accepting a new cartridge from the magazine, such that the process may be repeated rapidly . Shotguns utilise a similar mec hanism except that a collec tion of smaller projectiles – ‘shot’ – are expelled rather than a single bullet. These smaller projectiles disperse away from one another after leaving the barrel. T he degree of dispersal is dependent on the relative length of the barrel. External ballistics describe the characteristics of a projec tile in free ﬂight. It may be inﬂuenced by ammunition type and ambient conditions. Ammunition di ﬀ ers widely with the most pronounced di ﬀ erence between pistol and riﬂe ammunition. Riﬂes are expected to be accurate at ranges up to and beyond 1000 metres, while pistols are intended f or far shorter ranges. Riﬂe cartridges are longer and typically have a greater propor tion of propellant to projectile. The characteristics of ammuni tion that determine wound e ﬀ ects are the size or calibre (which describes the internal diameter of the weapon barrel) and the material components of the bullet: /uni25CF Full metal jacket ammunition has an outer coating of harder metal around a softer core. This reduces break down of the bullet along the barrel and improves accuracy , reliability and target penetration. /uni25CF Soft tip and hollow point ammunition have a degree of exposed lead that ﬂattens and deforms on impact. These bullets have less penetrating ability but rapidly transfer en ergy to the impacted tissue and cause large wounds. WEAPON EFFECTS Ballistics

- The ability to manage conﬂict injuries relies on an under - standing of the underlying mechanism of wounding, which - is likely to be di ﬀ erent from that in civilian trauma. As stated, while ballistic injuries are no longer the most common cause of battleﬁeld injur y , ﬁrearms remain a common element in all conﬂict. Civilian trauma practice, depending on local ﬁrearm laws, may well encompass a signiﬁcant volume of gunshot wounds, although patterns of injury with war wounds may well di ﬀ er as a result of the weapons used. An understanding of the mechanism of ballistic wounding is required to treat these wounds e ﬀ ectively . The earliest recorded depiction of a ﬁrearm is from 1326, but ﬁrearms became ubiquitous on the battleﬁeld during the 20 seventeenth century . Ballistic weapons all work with the same principles – an explosion is used to propel a projectile along and out of a straight tube – but have evolved considerably from rudimentary cannons to sophisticated modern-day ﬁrearms. The explosive force within a modern ﬁrearm comes from pro - pellant encased within a cartridge. The basic design of a car - tridge is shown in Figure 34.1 . - Internal ballistics describes the characteristics of a projec - tile while inside the weapon. The hammer mechanism strikes a primer at the base of the cartridge, which ignites the propel - lant. Hot gas produced by the explosion expands and forces the bullet away from the cartridge and along the bar rel. Spiral grooves, or riﬂing, impart spin on the bullet, which aids accu - e racy and stabilisation.

Bullet Propellant Casing Primer Figure 34.1 Diagram of basic cartridge structure.

- The ability to manage conﬂict injuries relies on an under - standing of the underlying mechanism of wounding, which - is likely to be di ﬀ erent from that in civilian trauma. As stated, while ballistic injuries are no longer the most common cause of battleﬁeld injur y , ﬁrearms remain a common element in all conﬂict. Civilian trauma practice, depending on local ﬁrearm laws, may well encompass a signiﬁcant volume of gunshot wounds, although patterns of injury with war wounds may well di ﬀ er as a result of the weapons used. An understanding of the mechanism of ballistic wounding is required to treat these wounds e ﬀ ectively . The earliest recorded depiction of a ﬁrearm is from 1326, but ﬁrearms became ubiquitous on the battleﬁeld during the 20 seventeenth century . Ballistic weapons all work with the same principles – an explosion is used to propel a projectile along and out of a straight tube – but have evolved considerably from rudimentary cannons to sophisticated modern-day ﬁrearms. The explosive force within a modern ﬁrearm comes from pro - pellant encased within a cartridge. The basic design of a car - tridge is shown in Figure 34.1 . - Internal ballistics describes the characteristics of a projec - tile while inside the weapon. The hammer mechanism strikes a primer at the base of the cartridge, which ignites the propel - lant. Hot gas produced by the explosion expands and forces the bullet away from the cartridge and along the bar rel. Spiral grooves, or riﬂing, impart spin on the bullet, which aids accu - e racy and stabilisation.

Bullet Propellant Casing Primer Figure 34.1 Diagram of basic cartridge structure.