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Medical Aspects of Blast Injuries: 

Medical Aspects of Blast Injuries Matthew D. Sztajnkrycer, MD, PhD Assistant Professor of Emergency Medicine Mayo Clinic sztajnkrycer.matthew@mayo.edu Amado Alejandro Báez MD Msc baez.amado@mayo.edu

Learning Objectives: 

Learning Objectives Discuss the epidemiology of blast injuries. Describe the physics of blast injuries. Describe special scenarios in the management of blast injuries.

Performance Objectives: 

Performance Objectives At the end of the course the student should be able to: Discuss the prehospital and hospital management of blast injuries.

Why Blast Injuries? : 

Why Blast Injuries? Deaths from terrorist acts: Oklahoma City 168 World Trade Center 2,801 Madrid train bombings 202 Tokyo sarin attack 12 American Anthrax 5

Physics of Blast Injuries: 

Physics of Blast Injuries Blast (shock) wave Pressure transmitted radially from source into surrounding medium. 3 components: Positive phase Negative phase Mass movement of wind (blast wind)

Slide6: 

Defining characteristic of conventional explosive is the variation in ambient pressure over time. During the positive phase, wave causes rapid increase in ambient air pressure (blast overpressure).

Slide7: 

Biological effects of a conventional blast depend primarily on: Peak overpressure Duration of positive phase

Blast Injury: 

Blast Injury Blast waves cause injury because of rapid external loading on the body and organs. May cause internal injury in air-containing organs without any external signs of trauma. Middle ear Lung GI tract

Categories of Blast Injury: 

Categories of Blast Injury Primary Secondary Tertiary Combined

Primary Blast Injury: 

Primary Blast Injury Direct concussive effect of the pressure wave on the victim. Shear effects at the air-tissue interface. More likely to occur in after detonation in an enclosed space.

Primary Blast Injury: 

Primary Blast Injury Organ most sensitive to the primary blast effect is the ear. Transient hearing loss generally resolves in first few hours after a blast. Up to 30% of victims may have permanent hearing loss. Essentially all severely injured patients have TM perforations.

Primary Blast Injury: 

Primary Blast Injury No patient with isolated TM perforation developed signs of pulmonary or GI blast injury. Eardrum Perforation in Explosion Survivors: Is It a Marker of Pulmonary Blast Injury? Leibovici D, Gofrit ON, and Shapira SC. Ann Emerg Med 1999;34: 168 - 172.

Primary Blast Injury: 

Primary Blast Injury Injury to lung is cause of greatest morbidity and mortality. Most obvious and consistent sign of pulmonary blast injury is hemorrhage. Classically, patients develop rapid respiratory deterioration with need for ventilatory support.

Primary Blast Injury: 

Primary Blast Injury Other pulmonary injuries include: Pneumothorax Hemothorax Pneumomediastinum Subcutaneous emphysema Air emboli

Air Emboli: 

Air Emboli Result from traumatic alveolar-venous fistulae. Responsible for most of the early mortality. More severe the pulmonary hemorrhage, the greater the likelihood of significant embolism.

Primary Blast Injury: 

Primary Blast Injury Gastrointestinal blast injury most commonly results in tissue tearing and hemorrhage. GI blast injury more commonly occurs after blast wave propagation in water. GI hemorrhage and perforation is most common in the lower small intestine or cecum, where gas accumulates.

Slide17: 

Secondary blast injury: Results from propelled objects striking victim. May be penetrating or blunt. Tertiary blast injury: Results from victim being propelled against structure by the blast wave or blast winds.

Slide18: 

Combined blast injury: Occurs when primary blast injury occurs in the setting of: Secondary or tertiary blast injury Burns Inhalational or toxic exposure Radiation

Prehospital Management: 

Prehospital Management Extrication and life support are the primary management priorities. In circumstances of building collapse, trend towards high mortality (90%). Extent of blast injury cannot be reliably assessed by typical rapid triage examination. Dogma: As a result, high over-triage rates are “mandated”.

History: 

History What type of explosive and how much? Where was victim located with respect to the blast? What did the victim do after the blast? Were fire/fumes present to cause inhalational injury? What was orientation of head and torso to the blast?

Hospital Management: 

Hospital Management Airway and ventilation management. Supplemental Oxygen PEEP/CPAP - watch for air emboli. Positive pressure ventilation and general anesthesia has been reported to increase mortality in blast injury. Surgery should be postponed 24 - 48 hours whenever possible.

Slide22: 

Consider abdominal films in all patients with significant blast injury. CT Scan Abdomen/Pelvis for patients with appropriate signs and symptoms. Hearing in both ears should be tested at bedside.

Slide23: 

Wound Management: Tetanus status. Local exploration. Delayed primary closure. IV followed by oral antibiotics for all but the most trivial wounds.

Special Scenarios - Homicide Bombings: 

Special Scenarios - Homicide Bombings Referred to as the “walking smart bomb.” Device typically consists of 10 -30 lbs of explosive. May also contain: Nails, bolts, ball bearings, or other secondary blast elements. Hazardous chemicals and pesticides. Bombers may have HIV, HepB.

Recognition: Stay ALERT: 

Recognition: Stay ALERT A: Alone and nervous L: Loose and/or bulky clothing E: Exposed wires (possibly through sleeve) R: Rigid mid-section (explosive device or other weapon) T: Tightened hands (may hold detonation device)

Radiation Dispersal Device (RDD): 

Radiation Dispersal Device (RDD) Conventional explosive used to disseminate radionuclide. “Dirty bomb” Nuclear explosion does not occur. Greatest radiation threat from device occurs prior to explosion.

Radiation Management: 

Radiation Management Radiation deaths are delayed. Management of conventional injuries and acute life threats takes precedence over radiation exposure. Treat injury first, then decontaminate.

Situational Awareness - Secondary Device: 

Situational Awareness - Secondary Device Emerging trend in terrorist bombings. First described in Northern Ireland. First used in the U.S. in 1997 in Georgia at abortion clinic bombings. A first device or dummy device lures first responders to the scene, where a secondary device detonates at a time to maximize responder casualties.

Summary: 

Summary Blast injuries remain a significant terrorist threat. Principal organs affected are the ear, lung, and intestine. Stay ALERT to the threat of homicide bombers.