Medical Aspects of Blast Injuries

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Medical Aspects of Blast Injuries

• Matthew D. Sztajnkrycer, MD, PhD
• Assistant Professor of Emergency Medicine
• Mayo Clinic
• sztajnkrycer.matthew_at_mayo.edu
• Amado Alejandro Báez MD Msc
• baez.amado_at_mayo.edu

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Learning Objectives

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

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Performance Objectives

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

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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

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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)

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• 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).

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

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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

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Categories of Blast Injury

• Primary
• Secondary
• Tertiary
• Combined

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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.

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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.

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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 199934 168 - 172.

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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.

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Primary Blast Injury

• Other pulmonary injuries include
• Pneumothorax
• Hemothorax
• Pneumomediastinum
• Subcutaneous emphysema
• Air emboli

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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.

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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.

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• 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.

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

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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.

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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?

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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.

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• 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.

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

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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.

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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)

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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.

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Radiation Management

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

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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.

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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.