Blast Injuries

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Author: Gregory Jasani, PGY-2

University of Maryland School of Medicine Department of Emergency Medicine

INTRODUCTION
Whether through an accident or intentional act, explosions have the potential to cause injuries to many people at the same time, resulting in significant morbidity and mortality and potentially overwhelming local healthcare resources. The resulting blast injuries are something that all emergency medicine providers need to be able to promptly recognize and treat.

Blast injuries are unfortunately not uncommon. In 2014, there were over 10,000 blast injuries in the United States due to fireworks. According to the Federal Bureau of Investigation, detonation of bombs or incendiary devices caused over 4,000 injuries and 448 deaths in the United States between 1987 and 1997.



Explosives are classified as either high-order or low-order. High-order explosives create a supersonic pressure wave known as the blast wave or shock wave. Examples of high-order explosives include trinitrotoluene (TNT), C-4, and dynamite. Low-order explosives by contrast create only subsonic pressure waves. Examples of low-order explosives include pipe bombs, gunpowder, and most petroleum-based explosives.

There are four mechanisms of injury in an explosion that providers need to be aware of: primary, secondary, tertiary, and quaternary.

PRIMARY
Primary blast injuries occur as blast waves move through the body, causing barotrauma. As only high-order explosives cause blast waves, primary blast injuries are unique to detonation of such explosives. Barotrauma affects air-filled organs more so than solid organs, commonly injuring organs such as the ears, eyes, brain, lungs, and gastrointestinal tract. Examples of blast-related barotrauma include the following:

• Blast ear: tympanic membrane rupture and middle ear damage
• Blast eye: globe rupture
• Blast lung: pulmonary contusion, pneumothorax, air embolism, and/or parenchymal damage
• Blast brain: injury to brain parenchyma
• Blast belly: abdominal hemorrhage and/or perforation

Blast injuries can be subtle and overlooked on initial evaluation. Of note, blast belly and blast lung may not initially be obvious on exam; patients can experience delayed presentations of up to 48 hours with either injury. Blast lung is the most common lethal injury among patients surviving the initial period post exposure.

SECONDARY
Secondary blast injuries occur when debris propelled by explosive forces comes into contact with a victim. Such debris can be part of the surrounding environment or may be a part of the explosive device itself. Bombmakers detonating explosives to cause harm to other humans may pack devices with objects such as nails or screws with the intent to injury as many people as possible.

Secondary injuries are the most common type of blast injury and can include fractures, amputations, dislocations, lacerations, or any type of soft tissue injury. Any part of the body can be subject to a secondary injury, though the head, neck, and extremities are the most common sites of injury. Explosive debris can travel faster than a bullet. Seemingly small entrance wounds may hide devastating internal injuries. Secondary injuries are the most common cause of mortality in patients exposed to blast injury.

TERTIARY
Tertiary injuries occur when the victim is propelled through the air by the blast wind and strikes another object, and/or when a structure collapses as the result of the explosion. Victims may experience blunt or penetrating trauma depending on what object is struck. The strength of the explosion typically determines the severity of the tertiary injuries sustained. Structural collapse can cause crush injuries and compartment syndrome. Providers should be aware that these patients are at high risk for hyperkalemia and should check an electrocardiogram (EKG) in these patients and avoid the depolarizing paralytic succinylcholine. Mortality increases the longer that victims remained trapped.

QUATERNARY
Quaternary injuries are injuries sustained as a result of an explosion that are not covered by primary, secondary, or tertiary categories. Accordingly, any injury that resulted from a fire secondary to the explosion would be classified as a quaternary injury. Quaternary injuries include those occurring from any exposure to biologic, chemical, or nuclear material. Quaternary injuries also include exacerbations of a victim’s underlying medical disease (i.e. chronic obstructive pulmonary disease exacerbation as a result of smoke inhalation) and/or any resultant psychiatric distress.

OTHER CONSIDERATIONS
Be sure to review your hospital’s disaster and/or mass casualty protocols. Remember that victims of an explosion will typically present in the reverse order of severity, with the least critically injured arriving for treatment first followed by more unstable patients. Keeping resources in reserve even as the first victims arrive is important to ensuring that these sicker patients will get prompt, potentially life-saving treatment as quickly as possible. Finally, be wary of the fact that these victims may have been exposed to biologic, chemical, or nuclear material.Take appropriate preventative and decontamination measures to keep yourself safe.

CONCLUSION
Unfortunately, blast injuries are not limited to battlefields. Regardless of the intent behind an explosion, we will see blast victims in our emergency departments. As emergency medicine providers, we need to have a thorough understanding of all forms of blast injuries so that when we see these patients we are able to provide the life-saving care that these victims need.

References:

1. Explosions and Blast Injuries A Primer for Clinicians. CDC. Available from: https://www.cdc.gov/masstrauma/preparedness/primer.pdf
2. Jorolemon MR, Krywko DM. Blast Injuries. [Updated 2019 Jun 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430914/