Introduction

Events such as the Boston Marathon bombing and the Manchester attack are reminders that terrorist attacks are of great concern to the general public. The various types of weapons of mass destruction (WMDs) can be remembered by the acronym CBRNE, which stands for chemical, biological, radiological, nuclear, and explosive weapons. This topic focuses on improvised explosive devices (IEDs).[1][2][3]

The United States Department of Defense defines IEDs as "devices placed or fabricated in an improvised manner incorporating destructive, lethal, noxious, pyrotechnic or incendiary chemicals, designed to destroy, disfigure, distract or harass." Explosive-related injuries were once thought to be related solely to combat medicine. Although the IED is considered one of the greatest threats to troops operating in Afghanistan during the War on Terror, they are not exclusively confined to the battlefield as civilian-targeted terrorist attacks like those mentioned above are becoming more commonplace. Kluger states that "[b]ombing and explosions directed against innocent civilians have become the primary instrument of global terror." It is of great importance that medical personnel be aware of the threat of terrorist-related IED attacks so that the appropriate steps can be taken if such an event were to occur.

Issues of Concern

Physics

Blast injuries are the classification of injuries that explosives can sustain, and to fully comprehend these injuries, practitioners must first understand the physics behind an explosion. Explosions occur due to an exothermic reaction generated when chemical bonds are disrupted. This ultimately causes the solid or liquid explosive material to be converted to a gas, rapidly expanding and releasing much energy. The explosion created by an IED can be classified into high-energy, which creates a supersonic high-pressure blast wave, or low-energy explosion, which creates a subsonic explosion without a blast wave. Examples of high-energy explosives include TNT, C4, Semtex, nitroglycerin, dynamite, and ammonia nitrate fuel oil. In contrast, materials like gunpowder and petroleum are examples of substances that cause low-energy explosions. Upon contact with a target, a significant amount of kinetic energy is dispersed, leading to the injury patterns described below.[4][5][6]

Blast Injury Classification  

Primary

A primary blast injury is a type of barotrauma that results from the interaction of a blast wave with the body. Hollow viscous organs such as tympanic membranes, the lungs, and the gastrointestinal organs are at particular risk in this type of blast injury. Blast lung injury (BLI) will be discussed below.

Secondary

Secondary blast injury results in penetrating trauma by bomb fragments and other projectiles. Some IEDs can be specifically enhanced with objects such as nails, metal ball bearings, or screws with the specific goal to cause a secondary blast injury and inflict as much trauma as possible. Energy from the explosive wave is transferred into the objects that act as high-energy or low-energy missiles.

Tertiary

A tertiary blast injury occurs when the victim becomes displaced due to the pressure wave. The victim is ultimately propelled and encounters a stationary object, such as a wall, which leads to direct, blunt trauma. This can lead to injuries such as traumatic brain injury, closed skull fractures, limb amputations, and musculoskeletal injuries.

Quaternary

Quaternary blast injury is a broader term to describe all other explosion-related injuries, which may include burns of various degrees or other types of toxic exposure.

Clinical Significance

Approach to IED-related Injury

The practitioner's clinical approach to explosive-related injuries depends on the provider's experience. Tactical Combat Casualty Care (TCCC) is a protocol-based, prehospital trauma care guideline specific to the battlefield. However, considering most prehospital providers responding to IED detonation will not be familiar with TCCC, responders need to implement advanced trauma life support (ATLS). The primary survey in ATLS consists of the ABCs, Airway, Breathing, and Circulation. However, in the case of an explosive detonation, exsanguination secondary to hemorrhage is an important caveat the responder must consider. Therefore, medical personnel should implement CABC, Catastrophic Bleeding, Airway, Breathing, and Circulation instead of ABC. The "C," standing for "Catastrophic Bleeding," reminds medical personnel that hemorrhage control should take precedence over airway security as exsanguination is associated with most potentially survivable deaths on the battlefield and, therefore, can be thought to have more deleterious outcomes as compared to airway compromise in the victim of an explosion. Moreover, hemorrhage is the second leading cause of civilian-related trauma death, furthering the idea that the CABC model is of great importance.[7][8][9]

Hemorrhage Control

Upon arriving at the scene of an explosion, there are important steps that medical professionals should take to control hemorrhage, as exsanguination is of great concern in such a situation. Therefore, direct pressure with sterile packing and applying a tourniquet is the mainstay of treatment for active bleeding. There are some recommendations that first responders should apply bilateral tourniquets to a victim of an explosion, even if there is no active bleeding, as it is thought that bleeding will likely occur when resuscitation with intravenous fluid is initiated. One study found that the application of the Combat Application Tourniquet (C-A-T^®) was an effective tool during civilian trauma (including terrorist events) to control extremity hemorrhage while offering few complications. Although other tourniquets like the Combat Ready Clamp (CRoC^®) and the Junctional Emergency Treatment Tool (JETT) are the preferred tools by military medics, familiarity with them by noncombat medical providers could prove to be very useful, as both devices have proved to occlude arterial flow in less than 1 minute.

In addition to using the tourniquet, hemostatic agents are another means responders can attempt to manage bleeding. The 2 products discussed below are part of the recommendations and guidelines of the Tactical Combat Casualty Care (TCCC). Although TCCC protocol is less likely to be known to civilian physicians and medical personnel, noncombat out-of-hospital providers should still be aware of the applicability of these products. One animal study compared the commonly used QuickClot Combat Gauze to the Food and Drug Administration (FDA)-approved XStat^® product and found that XSTAT subjects achieved hemostasis in less time, maintained hemostasis longer, and lost less blood than the QuickClot group. Additionally, tactical field care tranexamic acid (TXA), a recommended guideline by the TCCC, was found to reduce overall mortality related to hemorrhage.

Special Considerations: BLI

One special consideration of which providers treating victims of explosions should be aware is BLI. BLI results from barotrauma secondary to an explosive wave traveling through the air and is, therefore, an example of primary blast injury. BLI is secondary to pressure differentials generated upon tissues of different densities, ultimately leading to pulmonary hemorrhage, contusion, or edema. BLI is a clinical diagnosis based on respiratory difficulty and hypoxia in the appropriate setting, and patients with blast lung may present with dyspnea, cough, or chest pain. Complications of BLI secondary to an explosion include pneumothorax, hemothorax, fat embolism, and air emboli, which can enter the central nervous, ocular, or coronary arterial systems. As described above, the initial prehospital approach should focus on CABC. After the catastrophic bleeding has been addressed with direct pressure and tourniquet placement, the focus should be moved to the airway. Patients with suspected or confirmed BLI should have high-flow supplemental oxygen to prevent hypoxemia and receive endotracheal intubation for respiratory compromise. However, providers must be aware of mechanical ventilation and the risk of precipitating or worsening conditions like alveolar rupture, pneumothorax, or air embolism. Additionally, victims of explosions with suspected blast lung should be given fluids judiciously as overaggressive intravenous (IV) hydration can create volume overload and precipitate possible flash pulmonary edema.