Medical Aspects of Medical Aspects of Blast InjuriesBlast Injuries

Matthew D. Sztajnkrycer, MD, PhDMatthew D. Sztajnkrycer, MD, PhDAssistant Professor of Emergency Assistant Professor of Emergency

MedicineMedicineMayo ClinicMayo Clinic

sztajnkrycersztajnkrycer..matthewmatthew@@mayomayo..eduedu

Amado Alejandro Báez MD MscAmado Alejandro Báez MD Mscbaezbaez..amadoamado@@mayomayo..eduedu

Learning ObjectivesLearning Objectives

Discuss the epidemiology of Discuss the epidemiology of blast injuries.blast injuries.

Describe the physics of blast Describe the physics of blast injuries.injuries.

Describe special scenarios in Describe special scenarios in the management of blast the management of blast injuries.injuries.

Performance ObjectivesPerformance Objectives

At the end of the course At the end of the course the student should be the student should be able to:able to:

Discuss the prehospital Discuss the prehospital and hospital management and hospital management of blast injuries.of blast injuries.

Why Blast Injuries?Why Blast Injuries?

Deaths from terrorist acts:Deaths from terrorist acts:–Oklahoma CityOklahoma City 168 168–World Trade CenterWorld Trade Center 2,8012,801

–Madrid train bombingsMadrid train bombings 202 202–Tokyo sarin attackTokyo sarin attack 12 12–American AnthraxAmerican Anthrax 5 5

Physics of Blast InjuriesPhysics of Blast Injuries

Blast (shock) waveBlast (shock) wave–Pressure transmitted radially Pressure transmitted radially from source into surrounding from source into surrounding medium.medium.

–3 components:3 components:–Positive phasePositive phase–Negative phaseNegative phase–Mass movement of wind (blast Mass movement of wind (blast wind)wind)

Defining characteristic of Defining characteristic of conventional explosive is the conventional explosive is the variation in ambient pressure variation in ambient pressure over time.over time.

During the positive phase, wave During the positive phase, wave causes rapid increase in ambient causes rapid increase in ambient air pressure air pressure (blast overpressure). (blast overpressure).

Biological effects of a Biological effects of a conventional blast conventional blast depend primarily on:depend primarily on:–Peak overpressurePeak overpressure–Duration of positive Duration of positive phasephase

Blast InjuryBlast Injury

Blast waves cause injury because Blast waves cause injury because of rapid external loading on the of rapid external loading on the body and organs.body and organs.

May cause internal injury in air-May cause internal injury in air-containing organs without any containing organs without any external signs of trauma.external signs of trauma.

Middle earMiddle ear LungLung GI tractGI tract

Categories of Blast Categories of Blast InjuryInjury

PrimaryPrimary SecondarySecondary TertiaryTertiary CombinedCombined

Primary Blast InjuryPrimary Blast Injury

Direct concussive effect of the Direct concussive effect of the pressure wave on the victim.pressure wave on the victim.–Shear effects at the air-Shear effects at the air-tissue interface.tissue interface.

More likely to occur in after More likely to occur in after detonation in an enclosed detonation in an enclosed space.space.

Primary Blast InjuryPrimary Blast Injury

Organ most sensitive to the primary Organ most sensitive to the primary blast effect is the ear.blast effect is the ear.

Transient hearing loss generally Transient hearing loss generally resolves in first few hours after a resolves in first few hours after a blast.blast.

Up to 30% of victims may have Up to 30% of victims may have permanent hearing loss.permanent hearing loss.

Essentially all severely injured Essentially all severely injured patients have TM perforations.patients have TM perforations.

Primary Blast InjuryPrimary Blast Injury

No patient with isolated TM No patient with isolated TM perforation developed signs of perforation developed signs of pulmonary or GI blast injury.pulmonary or GI blast injury.

Eardrum Perforation in Explosion Survivors: Eardrum Perforation in Explosion Survivors: Is It a Marker of Pulmonary Blast Injury?Is It a Marker of Pulmonary Blast Injury?

Leibovici D, Gofrit ON, and Shapira SC.Leibovici D, Gofrit ON, and Shapira SC.

Ann Emerg Med 1999;34: 168 - 172.Ann Emerg Med 1999;34: 168 - 172.

Primary Blast InjuryPrimary Blast Injury

Injury to lung is cause of greatest Injury to lung is cause of greatest morbidity and mortality.morbidity and mortality.

Most obvious and consistent sign Most obvious and consistent sign of pulmonary blast injury is of pulmonary blast injury is hemorrhage.hemorrhage.

Classically, patients develop rapid Classically, patients develop rapid respiratory deterioration with respiratory deterioration with need for ventilatory support.need for ventilatory support.

Primary Blast InjuryPrimary Blast Injury

Other pulmonary injuries Other pulmonary injuries include:include:–PneumothoraxPneumothorax–HemothoraxHemothorax–PneumomediastinumPneumomediastinum–Subcutaneous emphysemaSubcutaneous emphysema–Air emboliAir emboli

Air EmboliAir Emboli

Result from traumatic alveolar-Result from traumatic alveolar-venous fistulae.venous fistulae.

Responsible for most of the early Responsible for most of the early mortality.mortality.

More severe the pulmonary More severe the pulmonary hemorrhage, the greater the hemorrhage, the greater the likelihood of significant embolism.likelihood of significant embolism.

Primary Blast InjuryPrimary Blast Injury Gastrointestinal blast injury most Gastrointestinal blast injury most

commonly results in tissue tearing commonly results in tissue tearing and hemorrhage.and hemorrhage.

GI blast injury more commonly occurs GI blast injury more commonly occurs after blast wave propagation in water.after blast wave propagation in water.

GI hemorrhage and perforation is GI hemorrhage and perforation is most common in the lower small intestine most common in the lower small intestine or cecum, where gas accumulates.or cecum, where gas accumulates.

Secondary blast injury: Secondary blast injury:

Results from propelled objects Results from propelled objects striking victim.striking victim.– May be penetrating or blunt.May be penetrating or blunt.

Tertiary blast injury: Results from Tertiary blast injury: Results from victim being propelled against victim being propelled against structure by the blast wave or blast structure by the blast wave or blast winds.winds.

Combined blast injury: Combined blast injury:

Occurs when primary blast Occurs when primary blast injury occurs in the setting of:injury occurs in the setting of:– Secondary or tertiary blast injurySecondary or tertiary blast injury– BurnsBurns– Inhalational or toxic exposureInhalational or toxic exposure– RadiationRadiation

Prehospital Prehospital ManagementManagement

Extrication and life support are the Extrication and life support are the primary management priorities.primary management priorities.

In circumstances of building collapse, In circumstances of building collapse, trend towards high mortality (90%).trend towards high mortality (90%).

Extent of blast injury cannot be Extent of blast injury cannot be reliably assessed by typical rapid reliably assessed by typical rapid triage examination.triage examination.

Dogma: As a result, high over-triage Dogma: As a result, high over-triage rates are “mandated”.rates are “mandated”.

HistoryHistory What type of explosive and how much?What type of explosive and how much? Where was victim located with respect Where was victim located with respect

to the blast?to the blast? What did the victim do after the blast?What did the victim do after the blast? Were fire/fumes present to cause Were fire/fumes present to cause

inhalational injury?inhalational injury? What was orientation of head and torso What was orientation of head and torso

to the blast?to the blast?

Hospital ManagementHospital Management

Airway and ventilation Airway and ventilation management.management.– Supplemental OxygenSupplemental Oxygen– PEEP/CPAP - watch for air emboli.PEEP/CPAP - watch for air emboli.– Positive pressure ventilation and Positive pressure ventilation and

general anesthesia has been reported general anesthesia has been reported to increase mortality in blast injury.to increase mortality in blast injury.

– Surgery should be postponed 24 - 48 Surgery should be postponed 24 - 48 hours whenever possible.hours whenever possible.

Consider abdominal films in all Consider abdominal films in all patients with significant blast patients with significant blast injury.injury.

CT Scan Abdomen/Pelvis for CT Scan Abdomen/Pelvis for patients with appropriate signs patients with appropriate signs and symptoms.and symptoms.

Hearing in both ears should be Hearing in both ears should be tested at bedside.tested at bedside.

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

Special Scenarios - Special Scenarios - Homicide Bombings Homicide Bombings

Referred to as the “walking Referred to as the “walking smart bomb.”smart bomb.”

Device typically consists of 10 -30 Device typically consists of 10 -30 lbs of explosive.lbs of explosive.

May also contain:May also contain:– Nails, bolts, ball bearings, or other Nails, bolts, ball bearings, or other

secondary blast elements.secondary blast elements.– Hazardous chemicals and pesticidesHazardous chemicals and pesticides..

Bombers may have HIV, HepB.Bombers may have HIV, HepB.

Recognition: Stay Recognition: Stay ALERTALERT AA:: Alone and nervousAlone and nervous LL:: Loose and/or bulky clothingLoose and/or bulky clothing EE:: Exposed wires (possibly Exposed wires (possibly through sleeve)through sleeve) RR: Rigid mid-section (explosive : Rigid mid-section (explosive device or other weapon)device or other weapon) TT:: Tightened hands (may hold Tightened hands (may hold detonation device)detonation device)

Radiation Dispersal Device Radiation Dispersal Device (RDD)(RDD)

Conventional explosive used to Conventional explosive used to disseminate radionuclide.disseminate radionuclide.–““Dirty bomb”Dirty bomb”–Nuclear explosion does not Nuclear explosion does not occur.occur.

–Greatest radiation threat from Greatest radiation threat from device occurs prior to explosion.device occurs prior to explosion.

Radiation ManagementRadiation Management

Radiation deaths are delayed.Radiation deaths are delayed. Management of conventional Management of conventional

injuries and acute life threats injuries and acute life threats takes precedence over takes precedence over radiation exposure. radiation exposure. –Treat injury first, then Treat injury first, then decontaminate.decontaminate.

Situational Awareness - Situational Awareness - Secondary Device Secondary Device

Emerging trend in terrorist bombings.Emerging trend in terrorist bombings. First described in Northern Ireland.First described in Northern Ireland. First used in the U.S. in 1997 in First used in the U.S. in 1997 in

Georgia at abortion clinic bombings.Georgia at abortion clinic bombings. A first device or dummy device lures A first device or dummy device lures

first responders to the scene, where a first responders to the scene, where a secondary device detonates at a time secondary device detonates at a time to maximize responder casualties.to maximize responder casualties.

SummarySummary

Blast injuries remain a Blast injuries remain a significant terrorist threat.significant terrorist threat.

Principal organs affected Principal organs affected are the ear, lung, and are the ear, lung, and intestine.intestine.

Stay ALERT to the threat of Stay ALERT to the threat of homicide bombers.homicide bombers.