Blast Injuries Blast Lung Injury
Blast lung injury • Blast lung injury (BLI) presents unique triage, diagnostic, and management challenges and is a direct effect of the blast wave from high explosive energy upon the body with a major cause of morbidity and mortality for the victims and among initial survivors. • The explosive impact upon the lung is tearing, hemorrhagic, contusive and edematous in nature resultanting in ventilation-perfusion mismatch. • BLI is a clinical diagnosis characterized by respiratory difficulty and hypoxia, which may occur without obvious external injury,eg. chest.
Diagnostic Evaluation • Chest radiography is necessary for anyone who is exposed to a blast with a characteristic “butterfly” pattern. • Arterial blood gases, computerized tomography, and doppler technology. • Most laboratory and diagnostic testing can be conducted per resuscitation protocols and further directed based upon the nature of the explosion (e.g. confined space, fire, prolonged entrapment or extrication, suspected chemical or biologic event.
Clinical Presentation • Symptoms : dyspnea, hemoptysis, cough, and chest pain. • Signs: tachypnea, hypoxia, cyanosis, apnea, wheezing, decreased breath sounds, and hemodynamic instability. • Associated pathology: bronchopleural fistula, air emboli, and hemothoraces or pneumothoraces. • Other injuries may be present.
Management • Initial triage, trauma resuscitation, treatment, and transfer should follow standard protocols; however some diagnostic or therapeutic options may be limited in a disaster or mass casualty situation. • In general, managing BLI is similar to caring for pulmonary contusion, which requires judicious fluid use and administration ensuring tissue perfusion without volume overload. • Clinical interventions • All patients with suspected or confirmed BLI should receive supplemental high flow oxygen sufficient to prevent hypoxemia (delivery may include non-rebreather masks, continuous positive airway pressure, or endotracheal intubation).
Blast Injuries: Essential Facts • Key Concepts • Bombs and explosions can cause unique patterns of injury seldom seen outside combat • Expect half of all initial casualties to seek medical care over a one-hour period • Most severely injured arrive after the less injured, who bypass EMS triage and go directly to the closest hospitals • Predominant injuries involve multiple penetrating injuries and blunt trauma • Explosions in confined spaces (buildings, large vehicles, mines) and/or structural collapse are associated with greater morbidity and mortality • Primary blast injuries in survivors are predominantly seen in confined space explosions • Repeatedly examine and assess patients exposed to a blast • All bomb events have the potential for chemical and/or radiological contamination • Triage and life saving procedures should never be delayed because of the possibility of radioactive contamination of the victim; the risk of exposure to caregivers is small • Universal precautions effectively protect against radiological secondary contamination of first responders and first receivers • For those with injuries resulting in nonintact skin or mucous membrane exposure, hepatitis B immunization (within 7 days) and age-appropriate tetanus toxoid vaccine (if not current)
Blast Injuries • Primary: Injury from over-pressurization force (blast wave) impacting the body surface • TM rupture, pulmonary damage and air embolization, hollow viscus injury • Secondary: Injury from projectiles (bomb fragments, flying debris) • Penetrating trauma, fragmentation injuries, blunt trauma • Tertiary: Injuries from displacement of victim by the blast wind • Blunt/penetrating trauma, fractures and traumatic amputations • Quaternary: All other injuries from the blast • Crush injuries, burns, asphyxia, toxic exposures, exacerbations of chronic illness • Primary Blast Injury
Lung Injury • Signs usually present at time of initial evaluation, but may be delayed up to 48 hrs • Reported to be more common in patients with skull fractures, >10% BSA burns, and penetrating injury to the head or torso • Varies from scattered petechiae to confluent hemorrhages • Suspect in anyone with dyspnea, cough, hemoptysis, or chest pain following blast • CXR: “butterfly” pattern
High flow O2 sufficient to prevent hypoxemia via NRB mask, CPAP, or ET tube • Fluid management similar to pulmonary contusion; ensure tissue perfusion but avoid volume overload • Endotracheal intubation for massive hemoptysis, impending airway compromise or respiratory failure • Consider selective bronchial intubation for significant air leaks or massive hemoptysis • Positive pressure may risk alveolar rupture or air embolism • Prompt decompression for clinical evidence of pneumothorax or hemothorax • Consider prophylactic chest tube before general anesthesia or air transport • Air embolism can present as stroke, MI, acute abdomen, blindness, deafness, spinal cord injury, claudication • High flow O2; prone, semi-left lateral, or left lateral position • Consider transfer for hyperbaric O2 therapy
Abdominal Injury • Gas-filled structures most vulnerable (esp. colon) • Bowel perforation, hemorrhage (small petechiae to large hematomas), mesenteric shear injuries, solid organ lacerations, and testicular rupture • Suspect in anyone with abdominal pain, nausea, vomiting, hematemesis, rectal pain, tenesmus, testicular pain, unexplained hypovolemia • Clinical signs can be initially subtle until acute abdomen or sepsis is advanced
Ear Injury • Tympanic membrane most common primary blast injury • Signs of ear injury usually evident on presentation (hearing loss, tinnitus, otalgia, vertigo, bleeding from external canal, otorrhea)
Other Injury • Traumatic amputation of any limb is a marker for multi-system injuries • Concussions are common and easily overlooked • Consider delayed primary closure for grossly contaminated wounds, and assess tetanus immunization status • Compartment syndrome, rhabdomyolysis, and acute renal failure are associated with structural collapse, prolonged extrication, severe burns, and some poisonings • Consider possibility of exposure to inhaled toxins (CO, CN, MetHgb) in both industrial and terrorist explosions • Significant percentage of survivors will have serious eye injuries
Disposition • No definitive guidelines for observation, admission, or discharge • Discharge decisions will also depend upon associated injuries • Admit 2nd and 3rd trimester pregnancies for monitoring • Close follow-up of wounds, head injury, eye, ear, and stress-related complaints • Patients with ear injury may have tinnitus or deafness; communications and instructions may need to be written
Impending airway compromise, secondary edema, injury, or massive hemoptysis requires immediate intervention to secure the airway. Patients with massive hemoptysis or significant air leaks may benefit from selective bronchus intubation. • Clinical evidence of or suspicion for a hemothorax or pneumothorax warrants prompt decompression. • If ventilatory failure is imminent or occurs, patients should be intubated; however, caution should be used in the decision to intubate patients, as mechanical ventilation and positive end pressure may increase the risk of alveolar rupture and air embolism. • High flow oxygen should be administered if air embolism is suspected, and the patient should be placed in prone, semi-left lateral, or left lateral positions. Patients treated for air emboli should be transferred to a hyperbaric chamber.
Disposition and Outcome • There are no definitive guidelines for observation, admission, or discharge following emergency department evaluation for patients with possible BLI following an explosion. • Patients diagnosed with BLI may require complex management and should be admitted to an intensive care unit. Patients with any complaints or findings suspicious for BLI should be observed in the hospital.
Discharge decisions will also depend upon associated injuries, and other issues related to the event, including the patient’s current social situation. • In general, patients with normal chest radiographs and ABGs, who have no complaints that would suggest BLI, can be considered for discharge after 4-6 hours of observation. • Data on the short and long-term outcomes of patients with BLI is currently limited. However, in one study conducted on survivors one year post injury, no patients had pulmonary complaints, all had normal physical examinations and chest radiographs, and most had normal lung function tests.