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