Chapter 4: Military-Related Injuries

Conflicts in far-reaching and diverse areas of the world have resulted in a myriad of traumatic injuries which health care providers are tasked to treat. Some military injuries are comparable to civilian traumatic injuries, while others are unique to wartime/conflict operations. Unfortunately, with the current state of terrorism, the line between the two is becoming more blurred, making it all the more important for all providers to be aware of what classically have been thought of as “military-related injuries.” In addition to the severity and pattern of injuries, the conflict environment itself adds an additional complexity to providing medical care in these situations. This chapter will provide an overview of the injuries traditionally associated with military operations, as well as highlight operational considerations. “Lessons learned” from our military colleagues can be lifesaving when applied to disaster situations no matter the location or specific circumstance.

While many surgical advances have been, and are being made, because of the vast experiences of military wartime trauma, many civilian injuries are treated in a similar fashion as military their counterparts. The sheer number of seriously injured in recent conflicts has allowed the military to further evidence-based transfusion practices. For example, the numerous multiple-injured military personnel have allowed for improved mortality in massive transfusion with the creation of 1:1:1 ratio protocols¹ and the addition of tranexamic acid.² In the end, however, these strategies are not significantly different from the massive transfusion protocols in place in civilian institutions. Similarly, splenic lacerations, whether sustained from a car crash in Missouri or an improvised explosive device (IED) detonating under a tank in Afghanistan, are treated the same. Furthermore, while traumatic brain injury (TBI) may be seen in an increased frequency in current military conflicts, its management is also comparable to its stateside counterpart. The military may be more in tune to the effects of repeat concussions, but the underlying management is the same. This chapter will highlight instances where military trauma varies from civilian trauma.

Before specific injuries are addressed, it is important to understand the basics of how a military member goes from being injured on the battlefield to eventual admission to a hospital in the United States. There are five levels of care described in the military aeromedical evacuation system.³ Unlike the American College of Surgery levels of trauma care, an increase in the military level represents an increase in medical capability.

Level I care is provided by the injured member themselves, other members of their unit, or a medic. This “Self-Aid/Buddy Care” allows for quick control of hemorrhage via pressure dressings, tourniquets, and topical hemostatic agents to stave off early hemorrhagic death. At this level, medical care is frequently complicated by the combat environment. Moving the injured to safety prior to providing medical care can be lifesaving for both the injured as well as the provider.

Level II is the first time a military member will encounter an advanced health care provider. Each branch of service has a slightly different medical team at this level, but it typically either consists of an area support facility staffed with a nonsurgeon advanced health care provider, or a mobile surgical unit which has basic general and orthopedic surgical capabilities. Units at this level typically have a holding capacity of 24 to 72 hours with supplies to support up to 10 operations each day for those 1 to 3 days without being resupplied, with specifics being dependent on the branch of service. Most of these units are modular in nature and can be supplemented with additional personnel and equipment to further enhance the medical care provided in the tactical environment.

Level III, the theater hospital, is approximately equivalent to a stateside Level III trauma center. This facility is still within the combat zone but has an increased capability, both in terms of the medical/surgical care and holding capacity. For example, Craig Joint Theater Hospital (CJTH), one of the Level III hospitals in support of Operation Enduring Freedom in Afghanistan, has advanced radiology support with computed tomography (CT), magnetic resonance imaging (MRI), and interventional radiology, as well as numerous subspecialty surgical services and 5 to 6 operating room tables. Holding capacity is increased to 44 to 248 beds and to 30 days.

Level IV is a major medical facility, still within the theater of war but outside the combat zone. Level V is a major medical center in the United States. These upper echelons have capabilities and staffing similar to civilian hospitals.

Where a patient enters the aeromedical evacuation chain depends on multiple factors, primarily proximity to medical facilities and severity of injury. While most point-of-injury care is provided by Level II facilities, if a member is injured near a Level III facility, then that is where they will receive their initial evaluation. Keep in mind that prior to entering any facility, all patients must be cleared—inspected for unexploded ordinance, booby-traps, or bombs. Safety is paramount while still trying to quickly evacuate the wounded out of the combat zone. For the Afghanistan theater the g oal is for patients to reach Level II within 1 hour from time of injury and to be transported to Level III within 24 hours. Transport from the point of injury to Level II is typically by ground or by tactical rotor aircraft. Transport between Levels II and III is also usually via tactical rotor aircraft under the medical supervision of Critical Care Air Transport (CCAT) teams given the smaller and more temporary nature of where these units are located. Transport between Levels III, IV, and V facilities is via fixed-wing aircraft. The goal is to have patients evacuated out to a Level IV facility within 48 to 72 hours from the time of injury. In all cases, the philosophy is to “get the right patient to the right hospital in the right amount of time,” while preserving the safety and security of all involved.^3,4

Spectrum of Injuries

Military-related injuries are comprised of battle and nonbattle injuries, with all possible mechanisms of traumatic injury being represented. In the military setting, these mechanisms of injury are not usually mutually exclusive; one patient may have penetrating wounds, blunt injuries, and blast trauma as well as burns, all from a single incident. Penetrating injury can be from gunshot wounds of varying caliber, knives, or flying projectiles from a myriad of explosive ordinance. Blunt mechanisms include falls, motor vehicle crashes, as well as assaults and sports-related injuries. Burns can occur from accidental or intentional household exposures, fires, explosions, or nuclear/radiation or chemical sources. The most common injury in recent conflicts is a result of explosive trauma, namely IEDs.

Distribution of Injuries

Since the advent of modern warfare, patterns of injury have remained remarkably constant. From World War I to the present, the anatomic distribution of wounds has remained approximately 60% to 70% to the extremities, 15% to the head, and 10% to each the thorax and the abdomen.⁵ Body armor is improving, becoming lighter and more flexible than in previous conflicts. The enhanced capability of body armor likely has contributed to the improved casualty to mortality ratio of 16:1 in Iraq and Afghanistan compared to 2.6:1 in Vietnam.⁶ Furthermore, the most common mechanism of injury is explosive trauma, with IED blasts being more common than gunshot wounds.

Projectiles

Projectiles cause injury through the creation of a permanent cavity as well as a temporary cavity. The permanent cavity is a result of the physical crush injury created by the projectile moving through tissue. The temporary cavity is created by a stretch injury from energy imparted to the tissues as the projectile travels. The permanent cavity is readily apparent at the time of injury, while the temporary cavity may not be as obvious at the initial evaluation. This tissue may initially look viable, but will ultimately become necrotic over time.

The specific characteristics of each type of projectile contribute to the overall damage that is caused. The most important of these characteristics are mass, velocity, depth of tissue penetration, yaw within the tissue, deformation, and fragmentation. KE is directly proportional to the mass and the square of the velocity of the projectile: KE = ½ mass × velocity². Thus, for two projectiles with the same kinetic energy, a large slow projectile will directly crush more tissue resulting in a larger permanent cavity, whereas a small fast projectile will impart more of its energy to the surrounding tissues causing more stretch and a larger temporary cavity.⁷

Yaw is defined as the angle between the projectile's long axis and its line of flight. A bullet can yaw during flight prior to encountering a target, or within the target tissue itself. The amount of yaw during flight is relatively inconsequential to the degree of tissue damage, affecting mainly the angle of entry, while the amount of yaw within the tissue contributes significantly to the amount of destruction caused. For example, Figures 4–1, 4-2, 4–3 compare the 7.62-mm AK-47 round, 5.6-mm M-16A1 round, and 7.62-mm M-14 or M-60 round with respect to anticipated permanent and temporary cavities. The M-16A1 round is lighter and faster than the AK-47 or M-14 rounds, with a much higher percentage of fragmentation. It also begins to yaw within a shorter distance, 10 to 15 cm, compared with 15 to 20 cm for the M-14 bullet and 25 cm for the AK-47. The characteristics of the M-16A1 lend to a greater amount of injury compared to the AK-47 or M-14, despite its being a smaller projectile.⁵

Explosive Ordinance

Explosive trauma is currently the most common cause of military-related injury. Depending on proximity to the explosion's epicenter, three distinct types of injuries are encountered: thermal, blast, and ballistic (Figure 4–4).⁵ Those closest to the explosion can be affected by the heat and flames of the explosion resulting in thermal or chemical burns of varying severity. Blast injury can present in three different classes of injury. Primary blast injury is a result of overpressure from the blast wave itself. All air-containing body structures are at risk of rupture when a victim experiences this sonic shock wave. A ruptured tympanic membrane is the most common injury sustained in blast trauma, followed by pneumothorax and gastrointestinal (GI) perforation. GI perforation can take up to 48 hours to manifest clinical symptoms, so a high index of suspicions is necessary to limit morbidity and mortality from a delayed diagnosis. Ballistic trauma, also classified as secondary blast trauma, is due to flying fragments. These fragments cause injury in a similar manner as projectiles, with permanent and temporary cavities. However, they are typically smaller, less uniform in shape, and impart lower amounts of energy. Ballistic trauma is classified both as secondary blast injury, for projectiles in the environment being thrown by the blast wind, or ballistic injury from fragments of the explosive device itself—either pieces of the explosive's casing or other objects deliberately placed in the explosive with the intent of causing injury as projectiles. The subtle difference between intentional and unintentional flying pieces of debris allows for ballistic trauma to be classified both with the category of blast trauma and is mentioned separately. Tertiary blast trauma is a result of the explosive force propelling the casualty into surrounding objects. This blunt force trauma results in injuries comparable with other types of blunt trauma, such as motor vehicle crashes or falls. Thus, a patient involved in a significant explosion can sustain burns, overpressure perforations, penetrating trauma, and blunt trauma simultaneously. A detailed thorough systematic evaluation is required to properly identify and address all injuries.

Not only does the type of explosive ordinance influence the injuries sustained, but also where that explosion occurs is of great importance. If the explosion occurs with the patient in a vehicle, it is termed a “mounted” IED event. An explosion triggered by a person outside of an armored vehicle is termed a “dismounted” detonation. In a mounted IED event, an IED or landmine explodes under an armored vehicle (Figure 4–5).⁵ The three forms of blast trauma can still affect the occupants, even though they may still be protected from the outside environment.⁵ Primary blast trauma exists from the blast wave overpressure. Secondary blast trauma exists from objects inside the vehicle becoming projectiles. Tertiary blast trauma exists as occupants collide with other occupants or portions of the vehicle. Furthermore, toxic gases can be released from the explosive device or the vehicle itself.

In a “dismounted” detonation, the person experiences significant explosive force directly beneath them, with the pressure wave driving debris upwards along fascial planes (Figure 4–6).⁵ Tissue far remote from the most distal site of injury can be damaged from the explosive force, much in the same way as the temporary cavity of a projectile is remote from the permanent cavity.

Given their prevalence worldwide and potential to cause devastating injuries, landmines and other explosive ordnance deserve further consideration. Landmines can be either antipersonnel or antivehicle depending on the intended trigger. Antipersonnel mines can be static, bounding, or horizontal spray.⁵ Static mines explode where they lie once pressure is applied to them, that is, stepped upon. Bounding mines have a separate explosive charge which causes the mine to “pop up” approximately 1 to 2 m prior to exploding. Horizontal spray mines expel fragments in a specific direction. This type of mine can be triggered via tripwire or command detonation. The location of the injuries inflicted depends greatly on the type of antipersonnel mine that is encountered. Static mines cause mainly lower extremity injuries, while bounding and horizontal spray mines can also cause torso injuries.

Another category of explosive ordnance is termed “explosive remnants of war” (ERW). This category is comprised of “unexploded ordnance” (UXO) and “abandoned explosive ordnance” (AXO). Both are unexploded devices. UXOs were deployed as weapons but did not properly explode whereas AXOs were left in an area of conflict without being attempted to be used. While UXO and AXO differ as to why they exist as unattended explosive ordnance in an area of current or former conflict, both types result in similar explosive injuries if detonated. Landmines and ERW are indiscriminant weapons. Personnel or vehicle—man, woman, or child—military or civilian—during an ongoing war or long after the conflict has been resolved—these ordinances affect all the same with devastating results.

According to figures reported by the International Campaign to Ban Landmines, in 2012 there were 3628 casualties of landmines and ERWs.⁸ These casualties were located in 62 countries. Approximately 78% of victims were civilians, with 47% of the civilians being children. While the total number of victims is decreased from 4474 reported in 2011, it is likely that these figures are an underrepresentation of the true morbidity and mortality sustained by these explosive devices. The emotional, physical, and financial toll of these injuries cannot be overestimated.

As mentioned earlier, combat operations in Iraq and Afghanistan have provided copious amounts of data to help develop improved transfusion strategies. From the analysis of these two wars, as well as large amounts of civilian data, massive transfusion protocols have been developed which provide for earlier transfusion of fresh frozen plasma and platelets, with improved mortality.⁹ The military continues with its civilian colleagues to determine the optimum transfusion strategy. Is it ratio driven? Is it guided by viscoelastic testing—thromboelastography (TEG) or rotational thromboelastometry (ROTEM)—in which whole blood clotting is examined?¹⁰ Military and civilian doctors alike are trying to create rational transfusion strategies which maximally benefit our patients while limiting the inherent risk associated with blood transfusion.

One area where the military differs from its civilian counterparts is the potential use of fresh whole blood. The military often operates in austere environments in which fractional blood components are not readily available, where supply lines are long, and where the limited supply of blood products, if existent at all, may not be adequate to correct the hemorrhagic shock and associated coagulopathy in the casualties present. In these dire circumstances, fresh whole blood (FWB) is an option.¹¹

FWB provides red blood cells (RBCs), clotting factors, platelets, and fibrinogen—all the components which are required to reestablish hemostasis. The blood is warm, thus not contributing to hypothermia, and is more functional, as clotting is not hampered by the loss of factor or platelet activity through cold storage. Additionally, the RBCs in FWB do not have the lessened oxygen delivery capacity from acquired storage lesions.

However, FWB does have disadvantages. Even with rapid testing for malaria, HIV, hepatitis B, hepatitis C, and syphilis, bloodborne transmission is possible. There is a theoretical increased risk of bacterial contamination given the decreased sanitary conditions inherent to most field conditions. Furthermore, given the chaotic situation in which FWB would be required, the chance of clerical error is increased, compounded by the fact that FWB must be type specific. If more than one person requires FWB, this increased risk for clerical error and a transfusion of incompatible blood is increased even more. Another strictly military consideration is that the donor, also a military member, will have a decreased exercise tolerance for a period of time while the body adjusts to the acute, albeit voluntary, blood loss. It must be remembered that in all situations, the success of the fight trumps any individual. Weakening the remaining fighting force is not a decision to be made lightly.

Nuclear Warfare

Another facet of military-related injuries involves nonconventional weapons. Unfortunately, with the increased activity of terrorist organizations these attacks have been seen in the civilian sector as well. A strong suspicion and good working relationship with the public health sector can greatly assist in determining if a nonconventional attack has taken place and how best to treat those already affected and prevent others from becoming affected.

A nuclear explosion has all the same explosive causes of injury as a conventional explosive—thermal, blast, and ballistic—with the addition of radiation. Radiation exposure requires decontamination prior to being brought into the medical facility, in the same manner as the safety clearance is performed. Triage is first based on a patient's conventional injuries, and then modified based on radiation exposure.¹²

Radioactive particles are classified as alpha, beta, gamma, and neutron. Alpha particles can be shielded by a sheet of paper and are harmful if internalized. Beta particles require a thicker material for shielding such as a layer of clothing or a few millimeters of aluminum. These can cause skin burns and are also harmful if ingested. Gamma particles and neutrons destroy living cells and are only shielded by a few feet of concrete or inches of lead. Radiosenstivity is directly correlated with mitotic rate, as only replicating cells are vulnerable to radiation's effects. Less mitotically active cells are affected only when larger doses of radiation are absorbed. Thus, a patient's symptoms can be used to estimate the amount of exposure incurred. Furthermore, these symptoms and their time-to-onset can be used to predict mortality as the adverse effects of radiation following a fairly consistent pattern.

Radiation exposure is expressed in gray (Gy) or rad. One Gy is equivalent to 100 rad which is equal to 1 J of energy per kilogram.¹³ LD₅₀ is defined as the dose which results in death of half of the people exposed. Exposure of 0.35 Gy can cause transient nausea or headache but is not classified as acute radiation syndrome (ARS). At least 2 Gy are required for ARS to develop.

The hematologic system is affected first with a decline in all cell lines. Radiation exposure affecting only the patient's bone marrow could be latent for 2 to 6 weeks, with the main symptom being fatigue. If there aren't other injuries prompting a medical evaluation, it is possible that medical attention would not be sought, even though it is direly needed. The GI system is affected next. At doses of 6 to 10 Gy, within 2 hours of exposure the patient will have acute-onset cramping abdominal pain, nausea, vomiting, and diarrhea as cells of the GI tract slough. Paradoxically, at doses greater than 10 Gy, nausea is suppressed. Early-onset diarrhea, especially without nausea, is a particularly poor prognostic sign. Neurologic symptoms, mainly ataxia, seizures, dizziness, and disorientation, suggest an exposure of greater than 10 Gy. Cardiovascular collapse occurs with doses of greater than 35 Gy.¹³

Without supportive care, the LD₅₀ is only 3.5 Gy. Death typically occurs within 60 days as a result of the patient's impaired immunity.¹³ With supportive care, namely fluids, antimicrobials, cytokines, and transfusion, the LD₅₀ increases to approximately 6 Gy. However, these LD₅₀s are based on radiation injury alone. If a patient sustains additional trauma, the LD₅₀ will decrease in accordance with the morbidity and mortality of the other injuries. Furthermore, while some conventional wounds are allowed to heal by secondary intention after repeated debridement, it is important for wounds in irradiated tissue to be closed primarily within 36 to 48 hours. Wounds in irradiated tissue left open for longer than this time frame serve as a source of infection.¹²

Treatment of radiation injury is primarily decontamination to prevent continuing exposure and symptomatic relief. Intravenous fluids are provided for hypotension and increased fluid losses from damaged skin and gastrointestinal cells. Antiemetics provide relief from nausea and vomiting, limiting further fluid losses. Lymphocyte counts can be very useful in determining if a lethal dose of radiation was experienced as well as for directing cytokine therapy. If lymphocyte counts are greater than 1.7 × 10³/μL, a fatal dose is unlikely. Patients with lymphocyte counts less than 300 to 500/μL can be considered for cytokine supplementation to counteract the radiation's effect on bone marrow. Given these suppressive effects, surgical procedures need to be delayed for weeks if possible, or completed within the first 36 hours. Other supportive measures include potassium iodide to prevent thyroid uptake of radioactive isotopes, chelating agents to bind absorbed metals, and Prussian blue to prevent gastrointestinal absorption of radionuclides.¹²

The evaluation of patients exposed to radiation needs to involve an accurate assessment of those who have a potential for survival. As a general rule, in any military mass casualty situation, if a patient presents with GI symptoms after radiation exposure their chance of survival is low enough and the anticipated utilization of resources is high enough that they will be triaged to “expectant,” and provided with comfort care measures.

Biological Warfare

Biological warfare also requires close communication between the medical care providers and public health officials. An attack should be suspected in scenarios with an unusual number of illnesses, unusual presentations, or simultaneous outbreaks, especially of diseases not endemic to the area. Weaponized biological agents can be difficult to identify, treat and isolate if a high index of suspicion is not maintained.

Prevention, protection, decontamination, and infection control are key while treating those suspected to be involved in a biological attack. Primary protection through vaccination is one of the most effective ways of minimizing the impact of a biological agent. Vaccination is possible for anthrax, plague, and smallpox. Postexposure chemoprophylaxis is available for anthrax, plague, Q fever, and tularemia. Decontamination, either mechanical via physical removal of the agent or chemical via destruction of the agent, helps to limit spread of the agent from people or clothing. Dilute bleach solutions are also effective for decontamination—either a 0.5% solution for skin or a 5% solution for equipment. Furthermore, ultraviolet (UV) light or heat can be utilized to effectively kill biological agents on inanimate objects.

The type of infection control precautions that are utilized depend on how the biological agent is transmitted. Universal precautions, consisting of hand washing, gloves, gown, eye protection, and masks, are always recommended when it is likely that body fluids may be encountered. When there is concern about transmission via droplets the patient should also be wearing a mask to limit the transmission of these larger particles. Droplet precautions should be instituted for Bordetella pertussis, influenza virus, adenovirus, rhinovirus, Neisseria meningitidis, and group A Streptococcus. Airborne precautions for particles less than 5 μm in size require special surgical masks/respirators. Agents which require airborne precautions include measles, varicella zoster, Legionella, disseminated herpes zoster, and tuberculosis. When possible, patients should be kept in private rooms or cohorted with others experiencing similar symptoms.

Table 4–1 lists known potential biological agents, likely symptoms, and appropriate medical management.¹⁴

Chemical Warfare

Toxic chemicals can be used intentionally as weapons, or released unintentionally from industrial accidents. Personal protective gear is required when there is a known threat or attack. Preventing exposure is key. Safe decontamination is paramount when exposure has already occurred. Specific antidotes should be provided as quickly as possible to limit morbidity and mortality. Table 4–2 lists many of the known chemical agents, mechanisms of action, symptoms, and treatments.^15,16 Surgical procedures can be safely performed after decontamination, but precautions must still be maintained. Double gloves should be worn, instruments should be cleaned with 5% bleach, and removed objects or tissue should be placed in bleach for disposal. Debridement should be performed with a no-touch technique as much as possible.

In most scenarios in the US civilian sector, resources are unlimited, personnel are plentiful, and the facility cannot be easily overwhelmed. In the military, the opposite is frequently true. In a mass casualty situation, resource and personnel limitations can force a change in triage principles that can be difficult to enact. As health care providers, we are usually trained to treat patients in a vacuum. Each patient's viability is based solely on the extent of their injuries. The sickest patient is treated first, but heroic measures will be available to all.

On the battlefield, the goals change. The battle itself remains the overarching goal. “Return the greatest number of soldiers to the fight” is the mantra. The sickest are not always treated first. “Limited resources” literally means that what is used for one patient is not available for the next. “Saving the greatest number of lives” equates to a patient who is deemed expectant in one situation may have been treated further in a less dire situation. Resources may need to be withheld from one so that multiple others may live. Mass casualty situations test not only medical skill, but emotional fortitude and resiliency as well.

Triage systems exist to prioritize patients for treatment. One common system utilizes 4 categories: immediate, delayed, minimal, and expectant.¹⁷ The immediate group requires lifesaving surgery or other intervention provided without delay. The delayed group also is likely to require lifesaving surgery; however for this group, surgery can be delayed for a short time without adversely affecting mortality as long as temporizing measures are provided. The minimal group is comprised of minor injuries, the care of which can be provided by nonmedical personnel or be delayed hours to days without adverse effect. Expectant patients are those who have injuries so extensive that the time or resources required to treat them with the goal of survival exceed that which are available. Expectant patients are provided with necessary pain control and other reasonable comfort measures but lifesaving measures are not pursued.

Another system divides patients into only 3 categories: emergent, nonemergent, and expectant. The emergent group can be thought of as those requiring immediate (within minutes) and urgent (within hours) intervention. Nonemergent patients still require care but do not currently have a threat to life, limb, or eyesight. Expectant patients are again those who, given the circumstances, have nonsurvivable injuries. No matter which system is utilized, the goal remains the same—to quickly identify which patients need attention first. It is important to remember that triage needs to be repeated. A patient's condition over time can change, requiring either an elevation in priority if they become more critical or perhaps even a change to expectant if their condition severely deteriorates or the overall situation becomes more dire with an influx of additional casualties. A successful medical operation in a mass casualty situation requires swift, accurate, and repeated triage.

In many ways, military-related injuries are treated in very much the same way as their civilian counterparts. However, some differences do exist. The injuries themselves can differ as military-related trauma can be caused by ordinances not typically encountered in the civilian environment. The priorities of treatment may vary as the strength of the remaining fighting force must be maintained. Returning members to the fight is a real consideration. What isn't different is the goal of “getting the right patient to the right hospital in the right amount of time.”