Blast Injury

Blast injury is a complex pattern of trauma that results from exposure to an explosion. Blast injury can occur with detonations—supersonic exothermic fronts that propagate through shock waves—as well as deflagrations—subsonic combustions that propagate through heat transfer. Detonations occur when high-order explosives (such as TNT and dynamite) transform into high-pressure gases that rapidly expand. Deflagrations occur with low-order explosives (like fireworks) that release energy slowly. Although explosions produce classic injury patterns, each event is unique and based primarily on the amount and composition of the explosive, the victim’s distance from the blast, and the surrounding environment.

Blast injuries are classified into four categories:

Primary injuries are caused by blast overpressure, which is the pressure generated by a shock wave. Thus, they most typically occur when a person is close to an explosive, and they occur with high-order explosives rather than low-orders explosives. They often involve injury to internal organs without external signs of trauma. The most commonly injured organs are the ears, lungs, and hollow gastrointestinal viscera, as air is easily compressible (unlike liquids or solids). Specifically, pulmonary barotrauma leads to a pattern of injury referred to as blast lung, which encompasses pulmonary contusion, alveolar swelling, air embolism, and other injuries; it is the most common cause of death among those who initially survive an explosion.

Secondary injuries result from fragmentation—the shattering of the casing of an explosive—or the propulsion of other objects caused by the explosion, such as shattered glass from a blown-out window. These injuries lead to penetrating trauma to any part of the body. They account for most deaths related to blast injury.

Tertiary injuries are caused by the blast wind generated by the explosion’s displacement of air. The wind can throw victims against solid objects, leading to both blunt and penetrating traumatic injuries.

Quaternary injuries refer to all other injuries not encompassed by the first three categories, including but not limited to burns, crush injuries, toxin exposure, and psychiatric injury, which is the most common quaternary injury.

Treatment of blast injuries follows the algorithm for other traumatic injuries. The principles of the primary survey should be followed, with attention to airway, breathing, circulation, disability, and exposure. Obvious penetrating injuries, blunt traumas, and burns should be treated per routine. However, due to the unique nature of primary blast injuries, special attention should be paid to tympanic membranes, lungs, and abdomen; a suspicion of primary blast injuries needs to be present even in the patient with no external evidence of trauma. Furthermore, it is essential to keep in mind that primary injuries may have a delayed presentation: blast lung and intestinal perforation can manifest as late as 48 hours after exposure to the blast.

References

Centers for Disease Control and Prevention: Blast and Bombing Injuries. emergency.cdc.gov

Champion HR, Holcomb JB, Young LA. Injuries from explosions: physics, biophysics, pathology, and required research focus. J Trauma. May 2009;66(5):1468-77.

DaPalma RG, Burris DG, Champion HR, Holcomb JB. Blast injuries. N Engl J Med. Mar 31 2005;352(13):1335-42.

Pennardt A, Kulkarni R, et al. Blast injuries. emedicine.medscape.com

Ritenour AE, Baskin TW. Primary blast injury: update on diagnosis and treatment. Crit Care Med. July 2008;36(7)S311-7.

Wightman JM, Gladish SL. Explosions and blast injuries. Ann Emerg Med. Jun 2001;37(6):664-78.

Thanks to Dr. Andrew Arndt for this post.