17971 - Medical Aspects of Blast Injuries Assistant...

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Unformatted text preview: Medical Aspects of Blast Injuries Assistant Professor of Emergency Medicine Mayo Clinic [email protected] Matthew D. Sztajnkrycer, MD, PhD Amado Alejandro Bez MD Msc [email protected] Learning Objectives s Discuss the epidemiology of blast injuries. s Describe the physics of blast injuries. s Describe special scenarios in the management of blast injuries. Performance Objectives s At the end of the course the student should be able to: s Discuss the prehospital and hospital management of blast injuries. Why Blast Injuries? s Deaths from terrorist acts: Oklahoma City Oklahoma City World Trade Center World Trade Center Madrid train bombings Madrid train bombings Tokyo sarin attack Tokyo sarin attack American Anthrax American Anthrax 168 2,801 202 12 5 Physics of Blast Injuries s Blast (shock) wave Pressure transmitted radially Pressure transmitted radially from source into surrounding medium. 3 components: 3 components: Positive phase Positive phase Negative phase Negative phase Mass movement of wind (blast Mass movement of wind (blast wind) s Defining characteristic of conventional explosive is the variation in ambient pressure over time. s During the positive phase, wave causes rapid increase in ambient air pressure (blast overpressure). s Biological effects of a conventional blast depend primarily on: Peak overpressure Peak overpressure Duration of positive phase Duration of positive phase Blast Injury s Blast waves cause injury because of rapid external loading on the body and organs. s May cause internal injury in air containing organs without any external signs of trauma. Middle ear s Lung s GI tract s Categories of Blast Injury s Primary s Tertiary s Secondary s Combined Primary Blast Injury s Direct concussive effect of the pressure wave on the victim. Shear effects at the airtissue Shear effects at the airtissue interface. s More likely to occur in after detonation in an enclosed space. Primary Blast Injury s Organ most sensitive to the primary blast effect is the ear. s Transient hearing loss generally resolves in first few hours after a blast. s Up to 30% of victims may have permanent hearing loss. s Essentially all severely injured patients have TM perforations. 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 s Injury to lung is cause of greatest morbidity and mortality. s Most obvious and consistent sign of pulmonary blast injury is hemorrhage. s Classically, patients develop rapid respiratory deterioration with need for ventilatory support. Primary Blast Injury s Other pulmonary injuries include: Pneumothorax Pneumothorax Hemothorax Hemothorax Pneumomediastinum Pneumomediastinum Subcutaneous emphysema Subcutaneous emphysema Air emboli Air emboli Air Emboli s Result from traumatic alveolar venous fistulae. s Responsible for most of the early mortality. s More severe the pulmonary hemorrhage, the greater the likelihood of significant embolism. Primary Blast Injury s Gastrointestinal blast injury most commonly results in tissue tearing and hemorrhage. s GI blast injury more commonly occurs after blast wave propagation in water. s GI hemorrhage and perforation is most common in the lower small intestine or cecum, where gas accumulates. s Secondary blast injury: Results from propelled objects striking victim. s Tertiary blast injury: Results from May be penetrating or blunt. victim being propelled against structure by the blast wave or blast winds. s 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 s Extrication and life support are the primary management priorities. s In circumstances of building collapse, trend towards high mortality (90%). s Extent of blast injury cannot be reliably assessed by typical rapid triage examination. s Dogma: As a result, high overtriage rates are "mandated". History s What type of explosive and how much? s Where was victim located with respect to the blast? s What did the victim do after the blast? s Were fire/fumes present to cause inhalational injury? s What was orientation of head and torso to the blast? Hospital Management s 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. s Consider abdominal films in all patients with significant blast injury. s CT Scan Abdomen/Pelvis for patients with appropriate signs and symptoms. s Hearing in both ears should be tested at bedside. s 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 s Referred to as the "walking smart bomb." s Device typically consists of 10 30 lbs of explosive. s May also contain: Nails, bolts, ball bearings, or other secondary blast elements. Hazardous chemicals and pesticides. s Bombers may have HIV, HepB. Recognition: Stay ALERT s A: Alone and nervous s L: Loose and/or bulky clothing s E: Exposed wires (possibly through sleeve) s R: Rigid midsection (explosive device or other weapon) s T: Tightened hands (may hold detonation device) Radiation Dispersal Device (RDD) s Conventional explosive used to disseminate radionuclide. "Dirty bomb" Nuclear explosion does not occur. Greatest radiation threat from device occurs prior to explosion. Radiation Management s Radiation deaths are delayed. s Management of conventional injuries and acute life threats takes precedence over radiation exposure. Treat injury first, then Treat injury first, then decontaminate. s Emerging trend in terrorist bombings. s First described in Northern Ireland. s First used in the U.S. in 1997 in Situational Awareness Secondary Device Georgia at abortion clinic bombings. s 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 s Blast injuries remain a significant terrorist threat. s Principal organs affected are the ear, lung, and intestine. s Stay ALERT to the threat of homicide bombers. ...
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