Blast Injury

Blast injuries are categorized as primary to quaternary, and sometimes quinary [1]. High-order explosives (HE) such as trinitrotoluene (TNT) engender high-pressure shock waves, which are the source of primary blast injuries (PBIs). HEs can cause the full spectrum of injuries, while low-order (LE) explosives such as petrol bombs, do not cause primary blast injuries (PBIs).

PBIs are mainly found in air-filled cavities in the body, the most frequently affected organs being the ears, lungs, and intestines. Ear damage is often presented as perforation of the tympanic membrane, middle ear damage, hearing loss, tinnitus, ear pain, and otorrhea [2]. Blast injury to the lung is a potentially fatal injury. It typically manifests as apnea, bradycardia, and hypotension, and other symptoms and signs include chest pain, tachypnea, dyspnea, cough, and hemoptysis. These signs arise from the lung injury itself, in addition to a cardiovascular response to the injury, manifesting as decreased cardiac output and a fall in blood pressure. Further consequences of blast lung injury are air embolism, lung contusion, acute respiratory distress syndrome (ARDS), and disseminated intravascular coagulation (DIC).

Abdominal PBIs, demonstrated by perforation of a hollow viscus, hemorrhage, and lacerations of solid organs, clinically emerge as oligemia, acute abdomen, vomiting with or without blood, and significant abdominal pain. Nevertheless, some display no outward signs initially [3]. PBIs may also cause brain injury by impairing blood flow and perfusion [4] [5]. Brain damage results from secondary and tertiary blast injuries as well.

Secondary blast injuries constitute the greater number of injuries and are the result of bomb fragmentation and airborne debris culminating in body penetration and blunt trauma [6] [7]. Tertiary blast injuries occur due to the impact against other objects when an individual is thrown by the force of the explosion. Those near the center of the blast and children are most vulnerable, so they frequently sustain fractures and may lose limbs. Quaternary blast injuries result from added effects of an explosion not mentioned above, namely burns, crush injuries, falls, subjection to radiation and toxic substances. Quinary injuries include the injurious action of post-explosion environmental contaminants, such as radiation or bacteria.

If possible, information should be gathered about the type and location of the explosion. A triage system is important and should be geared to rapidly identify PBIs and crush injury.

Chest radiographs are routinely obtained for all casualties exposed to overpressure, particularly in the presence of respiratory symptoms. A butterfly-shaped radiologic finding could be observed with blast injury to the lungs. Computerized tomography scans are also very useful. Both techniques may be used to investigate intraabdominal injury if suspected. The focused abdominal sonography for trauma (FAST) may be used to rapidly discern internal lesions that may not be immediately apparent and to determine the requirement for surgical intervention [8].

Laboratory tests include:

• Complete blood count, crossmatch and coagulation studies, as blood transfusion may be needed.
• Urinalysis is important as myoglobinuria indicates rhabdomyolysis. Also, it serves for the detection of renal injury.
• Acid-base parameters should be monitored, and carboxyhemoglobin measured; more so if the explosion happened within an enclosed space [9].
• Electrolytes levels, including calcium and phosphate, which may be deranged due to explosive chemicals.

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