Blast Injuries

Introduction

  • Occur more commonly than one might expect. A recent 20 year retrospective analysis of bombing events in the US identified 36,110 bombing incidents, 5,931 bomb-related injuries, and 699 bomb-related deaths between 1983 and 2002.1
  • Increasing frequency of both domestic and international terrorist bombing attacks has resulted in a large number of blast injuries previously seen only in military conflicts.2
  • Particularly because of the ever-present threat of terrorist acts, it is important for medical responders and emergency physicians to be well-versed in the spectrum of injuries that are associated with blasts.3

Recap Basics

Severity of blast injuries is affected by the location of the explosion, amount of explosives used, and the proximity and position of the victim in relation to the blast.3-5

Classification of blast injuries:

Primary
The direct effects of the blast wave passing through media of different density, such as air to tissue. Characteristically, this affects gas-containing organs such as the eardrums, lungs, and less commonly bowel. Blast lung is the most common cause of primary blast injury death.6,7
Secondary
Caused by the impact of airborne debris because of blast wind. Injuries may be caused by primary fragments (those that are integral to the bomb device) or by secondary fragments (those that come from the environment, such as wood or debris).5,6
Tertiary
Caused by displacement of the whole body. It can result from either structural collapse or displacement of the whole body by the blast wind and can typically manifest as blunt or crush injuries depending on the setting.5,8
Quaternary
Includes most other blast effects not categorized by primary to tertiary injury. These include burns, radiation exposure, inhalational injury, asphyxia, crush injuries, angina, hypertension, psychological consequences as well as others.5,6,8

What’s New

It was previously thought that since lower pressures are required to perforate the tympanic membrane (TM) than to damage other internal organs, that TM perforation could predict patients who potentially had more serious forms of primary blast injury (PBI).

  • What’s new: Multiple studies have shown that TM perforation is a poor predictor of blast injury. The absence of TM perforation does not appear to exclude other serious PBI, and in one study missed a range of up to 50% of those suffering a primary blast injury to the lung.10-14  Furthermore, several studies show that isolated eardrum perforation in survivors of explosions does not appear to be a marker of concealed pulmonary blast injury nor of a poor prognosis. Therefore, in a mass casualty event, persons with isolated TM rupture can be safely discharged from the ED after chest x-ray and a brief observation period.3
  • More accurate markers of severe blast injury include injuries to ≥4 body areas,  >10% total body surface area burns, skull and facial fractures, and penetrating injury to the head and torso. 15, 16

It was previously thought that blast victims may harbor serious injuries that will not be apparent during primary evaluation, such as blast lung.9

  • What’s new: Several studies show that this rarely happens.9, 17, 18 Most with pulmonary blast injuries have a fulminant clinical course evident soon after presentation.17

Previously, some advocated for the use of routine prophylactic bilateral chest tubes in those with blast lung injury.

  • What’s new: In the absence of pneumothorax, routine prophylactic bilateral chest tube placement is unnecessary and can be damaging to friable blast-injured lung. It may however, be considered prior to air transport and in those who respond inadequately to intubation and mechanical ventilation. 9,19

Management Pearls & Pitfalls

  • Pure blast injury can result in little evidence of external trauma.6
  • First treat any blast injury patient with ATLS algorithms. After stabilization, evaluation of those organ systems specifically affected by blast injury should be initiated.20
  • Blast lung injury can be diagnosed on repeat physical exam by looking for tachypnea, respiratory distress, hemoptysis, hypoxia, etc.9
  • Lung contusions are the hallmark of blast lung; they are often multiple, diffuse, and bilateral.9
  • Blast lung injury is radiographically identified by patchy or fluffy ill-defined infiltrates resembling a “butterfly” or “bat wing”. Occasional pneumothoraces may also be seen. These infiltrates are usually abrupt in onset and rapidly clear. If it does not clear it usually signifies a more significant underlying disease such as ARDS, PNA, or aspiration.19,20
  • Limit fluid administration for blast injury patients as they are at risk of pulmonary edema.6,11,19
  • Blast lung injury is arguably the most challenging blast injury to treat; the clinical picture is a mix of ARDS and air embolism.13 Mechanical ventilation with positive pressure ventilation can decrease the work of breathing and improve gas exchange, but it can increase the incidence and severity of both arterial air embolism and thoracic barotrauma.20,21 In the event of mechanical ventilation for primary blast lung injury, a lung protective strategy should be employed. Tidal volume, respiratory rate, inspiratory flow rate, and I:E ratio should be adjusted to minimize peak airway pressures. If necessary, permissive hypercapnea may be used.22
  • Although not extensively studied, advanced ventilator support technologies for blast lung injury include pressure control ventilation, jet ventilation, high frequency oscillatory ventilation (HFOV), use of nitric oxide and even the use of ECMO as a last resort.7
  • ER thoracotomy is discouraged in those with significant blast lung injury. The noncompliant contused lung coupled with hemothorax will not allow adequate exposure for safe placement of an aortic clamp.9

Further Reading

  1. Kapur GB, Hutson HR, Davis MA, Rice PL: The United States twenty-year experience with bombing incidents: Implications for terrorism preparedness and medical response. J Trauma 2005;59:1436-1444.
  2. Champion HR, Holcomb JB, Young LA: Injuries from explosions: physics, biophysics, pathology, and require research focus. J Trauma 2009;66:1468-1477.
  3. Goh SH: Bomb blast casualty incidents: initial triage and management of injuries. Singapore Med J 2009;50(1):101-106.
  4. Stein M: Urban bombing: a trauma surgeon’s perspective . Scandinavian Journal of Surgery 2005;94:286-292.
  5. Golan R et al: The ins and outs of terrorist bus explosions: Injury profiles of on-board explosions versus explosions occurring adjacent to a bus. Injury 2013.
  6. Housden S: Blast injury: A case study. International Emergency Nursing 2012:20:173-178.
  7. Stein M, Hirshberg A: Medical consequences of terrorism: The conventional weapon threat. Surgical Clinics of North America 1999;70:1537-52.
  8. Peters P: Primary blast injury: An intact tympanic membrane does not indicate the lack of a pulmonary injury. Mil Med 2011;176(1):110-4.
  9. Alfici R, Ashkenazi I, Kessel B: Management of victims in a mass casualty incident caused by a terrorist bombing: Treatment algorithms for stable, unstable, and in extremis victims. Mil Med 2006 Dec;171(12):1155-1162.
  10. Finlay et al: Explosions and human health: The long-term effects of blast injury. Prehospital and Disaster Medicine 2012 Aug;27(4)385-391.
  11. Wolf et al: Blast injuries. Lancet 2009;374:405-15.
  12. Horrocks CL: Blast injuries: Biophysics, pathophysiology and management principles. JR Army Med Corps 2001;147:28-40.
  13. Kluger et al: The special injury pattern in terrorist bombings. Journal of the American College of Surgeons 2004;199(6):875-879.
  14. Harrison et al: Tympanic membrane perforation after combat blast exposure in Iraq: A poor biomarker of primary blast injury. The Journal of Trauma 2009 Jul;67(1):210-211.
  15. Almogy et al: Suicide bombing attacks: Can external signs predict internal injuries? Annals of Surgery 2006;243(4):541-546.
  16. Almogy G, Luria T, Richter E et al: Can external signs of trauma guide management? : Lessons learned from suicide bombing attacks in Israel. Arch Surg 2005;140:390-393.
  17. Leibovici D, Gofrit ON, Shapira SC: Eardrum perforation in explosion survivors: Is it a marker of pulmonary blast injury? Ann Emerg Med 1999 Aug;34(2):168-72.
  18. Pizov et al: Blast lung injury from an explosion on a civilian bus. Chest 1999;115(1):165-172.
  19. Yeh DD, Schecter WP: Primary blast injuries—an updated concise review. World J Surg 2012 May;36(5):966-72.
  20. Guzzi LM and Argyros G: The management of blast injury. European Journal of Emergency Medicine 1996 Dec;3(4):252-5.
  21. Philips Y: Primary blast injuries. Annals of Emergency Medicine 1986;15(12):1446-1450.
  22. Sorkine P, Szold O, Kluger Y et al: Permissive hypercapnia ventilation in patients with severe pulmonary blast injury. J Trauma 1998;45:35-38.
Edited by Alex Koyfman, MD

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