Background

Blast injuries stem from the instantaneous transformation of a substance from solid or liquid to gas, releasing energy in the form of heat, light, pressure, and sound. While rare, blast injuries carry a high rate of morbidity and mortality.

  • Blast injuries commonly have a mixed presentation of blunt and penetrating trauma. Burns, crush injuries, and resource limitations may complicate their treatment.
  • Repeat surveys for injury are necessary, as specific injuries can be missed or evolve following the initial exam. 

Epidemiology: 

  • The global prevalence of blast injuries has tripled in the last decade, many due to improvised explosive devices or suicide attacks in warfare.
  • While the majority of casualties from blast injuries are in war zones, there has also been a recent increase in attacks involving civilians.

Objective:

  • Based on current evidence, this review article aims to guide the Emergency Department (ED) in providing care for patients with blast injuries.

 

Types of Injury:

  • Primary: Injury caused by the blast wave. It most commonly affects gas-containing organs.
    • Organs: tympanic membrane, lungs, and bowel
    • Injuries: tympanic membrane perforation, hemothorax, pneumothorax, arterial gas embolism, intestinal perforation, and globe rupture.
    • Most common cause of death:
      • Blast lung: Alveolar capillary rupture resulting in hemorrhage, pulmonary edema, reduced gas exchange, hypoxia, and hypercarbia
  • Secondary: Injury caused by direct impact of debris such as shrapnel or environmental fragments due to the blast wind.
    • Injuries: Soft tissue wounds and globe penetration
  • Tertiary: Injury caused by transposition of the body from the blast wind or a structural collapse.
    • Injuries: Traumatic amputations, bony fractures, and brain injuries
  • Quaternary: Injury caused by the environment
    • Injuries: Burns, inhalational injury, radiation, crush injuries, psychological effects, bacterial contamination
  • Quinary: Injury caused by a delayed hyper-inflammatory response due to chemicals associated with the blast and may last from hours to days.
    • Injuries: Hyperpyrexia, diaphoresis, low central venous pressure, positive fluid balance

Organ Systems:

  • Auditory:
    • Affected by the primary blast wave causing a tympanic membrane rupture.
    • Signs and symptoms may include dizziness, hearing loss, otalgia, tinnitus, and hemotympanum.
    • All patients must undergo an otoscope examination and be questioned about hearing loss and tinnitus due to the high prevalence of tympanic membrane perforation.
    • Management of blast tympanic membrane perforations differs from typical ruptures:
      • Patients may benefit from urgent otolaryngology evaluation due to the high rate of large perforation, reduced spontaneous healing, and need for operative intervention.
    • If the ear is contaminated with debris or shows signs of secondary infection, consider treatment with fluoroquinolone and a steroid-containing topical antibiotic.
  • Neurologic:
    • Affected by the primary blast wave causing a traumatic brain injury.
      • TBI may also be caused by secondary and tertiary injury from blunt trauma.
    • Immediate Injuries: gas emboli leading to infarction, cerebral contusion, cerebral edema, diffuse axonal injury, and extra-axial hematoma.
    • Delayed Injuries: Inflammatory response, vasospasm, secondary ischemia, post-traumatic stress disorder, depression, anxiety, insomnia, lethargy, fatigue, poor concentration, and post-concussive syndrome.
    • Treat by avoiding hypoxia, hypercarbia, hypotension, hypothermia, and hypoglycemia.
    • Traumatic brain injury is the leading cause of mortality in blast victims.
  • Pulmonary:
    • Affected by the primary blast wave causing pulmonary blast injury.
    • Signs and symptoms: Dyspnea, hypoxia, cough, hemoptysis, decreased breath sounds, rhonchi, and tachycardia.
    • Immediate Injuries: Rupture of alveolar capillaries, intrapulmonary hemorrhage, pulmonary contusion, pneumothorax, hemothorax, respiratory distress, hypoxia, and air embolism leading to cardiogenic shock or cardiac arrest.
    • Delayed Injuries: Leukocyte accumulation causes cell damage, leading to acute respiratory distress syndrome, which peaks at 48 hours.
    • Chest radiography has poor sensitivity in diagnosing blast lungs. Computed tomography (CT) may better demonstrate injuries. 
    • Treatment: Oxygen, avoid hyperoxia, chest thoracostomy as needed, and invasive/non-invasive ventilation while avoiding PEEP, using low tidal volumes and high respiratory rates when possible. 
  • Cardiovascular:
    • Injury: cardiac contusion, wall rupture, tamponade, papillary muscle rupture, valve injury, aortic arch injury, and coronary artery dissection.
      • Thoracic compartment syndrome may occur due to mediastinal hematoma and/or edema during positive pressure ventilation.
    • A unique form of cardiogenic shock can occur involving myocardial depression without peripheral vasoconstriction due to the vagal reflex, resulting in relative bradycardia despite hemorrhage.
    • Obtain an EKG on all patients with blast exposure who present with chest pain, dyspnea, or hemodynamic instability. Obtain a troponin and echocardiogram if a cardiac injury is suspected, a new arrhythmia is present, or the patient is hemodynamically unstable.  
    • When cardiac dysfunction secondary to blast exposure is suspected, reduce positive pressure ventilation and inotropic support due to likely associated lung injury. 
  • Abdomen:
    • Injuries: bowel rupture, infarction, ischemia, hemorrhage.
    • CT with oral contrast has a poor sensitivity for abdominal injury. Thus, repeat evaluation and monitoring of symptoms are critical.
    • Symptom onset may be delayed up to 14 days after blast exposure.
  • Ophthalmologic:
    • Affected by both primary and secondary blast waves.
    • Consider shrapnel and pressure-based injuries such as corneal abrasion, foreign body, and globe rupture. 
  • Musculoskeletal:
    • Fractures and amputations are some of the more frequent injuries seen after blast exposure.
  • Dermatologic:
    • Soft tissue injury is the most common injury in blast victims. 
    • Due to contamination, wounds require extensive irrigation, broad-spectrum antibiotics, and tetanus prophylaxis. 
      • In less complex wounds, delayed primary closure should be considered.
      • Wounds are most commonly infected with Acinetobacter species.
      • Wounds are also at high risk for invasive fungal infections.
    • Patients exposed to blast injury often concomitantly have burn injuries depending on the type of explosive and setting of explosion. 
    • Treatment emphasis centers on fluid resuscitation; however, consider transfer to a hospital with burn and trauma specialists.
      • It is crucial to weigh the benefits of fluid resuscitation against the possible complication of the patient developing blast lung injury, which can be increasingly severe in settings of fluid overload.
    • Patients with burn injuries should be assessed for inhalation burns and carbon monoxide poisoning.
  • Crush Injuries: 
    • A crush injury occurs when a body part is compressed, causing muscle edema and neurovascular compromise. This leads to metabolic changes and third spacing in the affected body part.
      • Swelling may also lead to compartment syndrome, which requires compartment pressure measurement and fasciotomy.
    • Reperfusion of a crush injury can lead to the release of toxic cell breakdown metabolites throughout the body, which can lead to metabolic derangements, hypotension, and cardiac arrhythmias. 
    • Early mortality in crush syndrome occurs due to hyperkalemia and hypovolemia, which highlight the importance of close cardiac monitoring and hydration.

Mass Casualty Incident Considerations:

  • Due to the nature of blast exposures, physicians will often have to treat these injuries in the setting of a mass casualty incident. 
  • An upside-down triage model can be expected, where the most severely injured patients arrive after the less injured patients bypass the emergency medical services system and arrive via private means. 
  • The first wave of casualties may be estimated by doubling the first hour’s casualties. 
  • Consider plain films and ultrasound imaging before CT due to speed and decreased demand on the system.
    • Ultrasonography: Can evaluate for free fluid in the abdomen, fluid or inappropriate air in the chest cavity, and cardiac tamponade.
    • Plain radiographs: Can evaluate for fractures and dislocations, fluid or inappropriate air in the chest cavity, characteristics of blunt lung injury, foreign bodies, and abdominal perforation.
  • If a patient is critically ill and will obtain CT, avoid CT imaging of individual body parts and proceed with a full-body CT due to limited resources and time. 
    • CT has poor sensitivity for detecting mesenteric and bowel injuries without oral contrast and blunt cardiac injury.

Scene Characteristics:

  • Scene Safety: 
    • When performing on-scene recovery, consider damage from the explosion, such as unstable structures, secondary explosive devices, shrapnel, fuel exposure, smoke exposure, fire exposure, and inhalation of damaging substances.
    • Enclosed spaces enhance the effect of the primary blast wave, resulting in more significant injury due to rebound and reflection.
    • To combat these dangers, emergency responders should wear personal protective equipment such as eye protection, breathing masks specialized for fumes, hard hats, and heavy gloves. 
    • A staging and triage area is recommended as a lack of effective staging and triage can lead to the spread of biological/chemical contamination from an explosive device or poor patient distribution among available hospitals. 

Commonly Missed Injuries:

  • As the primary blast wave can cause significant internal injury without evidence of external damage and multiple blast-related injuries may develop over the hours and days following exposure, delayed and missed diagnoses are more common, thus requiring excellent patient education and return precautions.
  • Most commonly overlooked injuries include concussion, soft tissue damage, PTSD, nerve damage, hearing loss, and chronic infection.

Author's Conclusions

  • Due to the potential for multi-organ system impact, blast injuries must be evaluated systematically, highlighting investigation for blast-specific injuries.
  • Understanding blast-injury patterns is crucial to avoid misdiagnosis of patients with polytrauma.

Our Conclusions

  • This comprehensive review article adeptly outlines the diverse spectrum of injuries that patients can experience from blast-related exposures, shedding light on an uncommon but high mortality and morbidity segment of emergency medical care. This article may apply to a broader audience of clinicians by including data from military and civilian blast incidents. While this article primarily focuses on injuries that would occur in the immediate setting, clinicians can better customize patient discharge education and return precautions by elucidating injuries that may develop over time.

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Citation: Bukowski J., Nowadly C.D., Schauer S.G., et al. High Risk and Low Prevalence Disease: Blast Injuries. American Journal of Emergency Medicine. 2023;70:46-56.