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Blast injury

Dr Vincent Ioos

Medical ICU

PIMS

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Introduction

• Area affected: Irak, Israel, Pakistan, Madrid,

9/11, Beirut…

• Main publications: civilian (Israel), military

(Irak)

• Particularities of blast injury

• Management of mass casualty events

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Classification of explosives (1)

• Explosives are categorized as high-order

explosives (HE) or low-order explosives (LE).

• HE produce a defining supersonic over-

pressurization shock wave. Examples of HE: TNT, C-4,

Semtex, nitroglycerin, dynamite, and ammonium nitrate fuel oil

(ANFO).

• LE create a subsonic explosion and lack HE’s

over-pressurization wave. Examples of LE: pipe bombs,

gunpowder, and most pure petroleum-based bombs such as Molotov cocktails or aircraft improvised as guided missiles.

• HE and LE cause different injury patterns.

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Classification of explosives (2)

• “Manufactured” implies standard military-issued, mass produced, and quality-tested weapons.

• “Improvised” describes weapons produced in small quantities (IED), or use of a device outsideits intended purpose, such as converting a commercial aircraft into a guided missile.

• Manufactured (military) explosive weapons are exclusively HE-based.

• Terrorists will use whatever is available

• Manufactured and improvised bombs cause markedly different injuries.

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Particularities of suicide blast

• High-grade explosive material used by theattackers;

• Ability of the attackers to detonate the explosive device in proximity to the victims by concealingthe explosive device and mingling within a crowd;

• Ability of the attacker to precisely time theexplosion at his or her discretion;

• Large load of heavy shrapnel that accompanythe explosive material.

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Blast wave

• The HE “blast wave” (over-pressure

component) should be distinguished from

“blast wind” (forced super-heated air flow),

encountered with both HE and LE.

• Expansion of gas creating a shock wave:

supersonic speed 3000 to 8000m/s

• Blast wave rapidly looses pressure and

velocity with distance and time

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Blast wave (2)

• Brisance: shattering ability of the blast front

• If closed space: overpressure magnified by

reflection off solid structures

• Open space: little primary blast injury because

of rapid decay of the blast wave

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Enhanced blast weapons

• A primary blast from these devices disseminates the

explosive and then triggers it to cause a secondary

explosion

• Air delivery, guided missiles, handheld weaponry

• Designed to enhance blast wave + thermal effect

• Lower peak pressure but longer sustained time of

blast overpressure

• Greater damage to soft structures and personnel

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Action of blast wave on the body

• Stress waves:

– Longitudinal pressure forces, supersonic speed

– Spalling effect at air-tissue interfaces

– Severe microvascular damage and tissue disruption

• Shear waves:

– Transversal waves

– Asynchronous movement of tissue

– Possible disruption of attachments

� ear, lungs, colon, gas-filled organs affected with the damage

initiating at the tissue-gas interface

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Primary blast injury

• Body armor does not protect against the barotraumaof primary blast injury

• Pulmonary barotrauma is the most common critical injury to people close to a blast center, whether civilian or military

• Systemic acute gas embolism from pulmonary disruption is believed to occlude the blood vessels of the brain or spinal cord

• Primary blast injuries are notorious for their delayed onset

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Closed versus open space

(greater primary blast injury)

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Blast Injuries: Bus Versus Open-Air Bombings-

-A Comparative Study of Injuries in Survivors of

Open-Air Versus Confined-Space Explosions

J Trauma Volume 41(6), December 1996, pp 1030-1035

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Blast Injuries: Bus Versus Open-Air Bombings-

-A Comparative Study of Injuries in Survivors of

Open-Air Versus Confined-Space Explosions

• An overall increased mortality rate with explosions in confined spaces.

• Immediate survivors of explosions within confined spaces suffer more severe injuries and present to the ED in a less favorable physiologic condition.

• Confined spaces: higher incidence of primary blast injuries, with a predominance of the more severe pulmonary injuries rather than perforation of tympanic membranes.

• Burns sustained by victims of explosions in confined spaces affect a larger BSA.

• No difference in the incidence of significant penetrating trauma, burns, or traumatic amputations between the two settings.

J Trauma Volume 41(6), December 1996, pp 1030-1035

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Blast lung (1)

• Direct consequence of the HE over-pressurizationwave.

• Most common fatal primary blast injury among initial survivors.

• Signs of blast lung usually present at the time of initial evaluation, but reported as late as 48 hoursafter the explosion.

• Blast lung is characterized by the clinical triad of apnea, bradycardia, and hypotension.

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Blast lung (2)

• Pulmonary injuries vary from scattered petechae

to confluent hemorrhages

• Blast lung should be suspected for anyone with

dyspnea, cough, hemoptysis, or chest pain

following blast exposure.

• Characteristic “butterfly” pattern on chest X-ray.

A chest Xray is recommended for all exposed

persons

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Ear blast injury

• Significant morbidity, but are easily overlooked.

• Dependent on the orientation of the ear to theblast.

• TM perforation is the most common injury to themiddle ear.

• Signs of ear injury are usually present at time of initial evaluation: hearing loss, tinnitus, otalgia, vertigo, bleeding from the external canal, TM rupture, or mucopurulent otorhea.

• All patients exposed to blast should have an otologic assessment and audiometry.

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Blast abdominal injury

• Gas-containing sections of the GI tract mostvulnerable to primary blast effect.

• Bowel perforation, hemorrhage (ranging fromsmall petechiae to large hematomas), mesenteric shear injuries, solid organlacerations, and testicular rupture.

• abdominal pain, nausea, vomiting, hematemesis, rectal pain, tenesmus, testicularpain, unexplained hypovolemia, or anyfindings suggestive of an acute abdomen.

• Clinical findings may be absent until the onset of complications.

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Blast brain injury

• Primary blast waves can cause concussions or mild traumatic

brain injury (MTBI) without a direct blow to the head.

• Primary blast injury can also result in cranial fractures around

air-filled sinuses and focal neurologic deficits as a result of air

embolism

• Consider the proximity of the victim to the blast particularly

when given complaints of headache, fatigue, poor

concentration, lethargy, depression, anxiety, insomnia, or other

constitutional symptoms.

• the signs and symptoms of postconcussion syndrome overlap

with those of PTSD

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In the field (1)

• Scoop and run approach

• Needle thoracostomy or endotracheal

intubation, early use of tourniquet may be life

saving

• Victims with amputated body parts and no sign

of movement + those with no pulse and fixed

dilated pupils are considered dead: no further

effort

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In the field (2)

• Objects that are impaling a person should be

removed or manipulated only in an operating

room.

• To facilitate the transport of impaled patients,

the objects can be cut or shortened.

• Transporting patients with long-bone fractures

requires temporary splinting to manage pain

and also to avert further soft-tissue damage

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Injury Severity Score / AIS

• Abbreviated injury scale: categorize the injuries of victims of motor vehicle collisions.

• Severity from 1 (least severe) to 5 (survival uncertain) within six body regions: head/neck, face, chest, abdominal/pelvic contents, extremities, and skin/general. Nonsurvivable conditions are assigned an AIS of 6.

• The AIS does not accurately measure the effects of multiple injuries. It is used in coding injuries for other scoring systems or for outcome analysis systems

• Injury Severity Score — The ISS is calculated from the AIS for the three most severely injured regions :

ISS = (AIS1) squared + (AIS2) squared + (AIS3) squared

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ISS / other scoring system

• ISS limited by:

– its inability to adjust for the cumulative effect of coexisting injuries in one region (eg, subdural hematoma and intraparenchymal hemorrhage),

– the lack of a direct linear relationship between increasing score and severity,

– the lack of consideration of preexisting conditions that may affect trauma outcomes.

– ISS is a valid predictor of mortality, length of stay in the hospital or intensive care unit, and cost of trauma care.

• RTS (systolic BP, respiratory rate, GCS)

• TRISS (ISS +RTS)

• START: Simple Triage and Rapid Treatment

• …

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Damage control surgery

• Surgical concept: « the best operation for a patient is

one, definite procedure »

• Multiple trauma patients die from coagulopathy,

hypothermia, meabolic acidosis

• DCS: control of haemorrhage, prevention of

contamination and protection from further injury

• ICU: warming, correction of acidosis and

coagulopathy…

• Staged procedure (definitie surgical procedure)

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White phosphorus burns (1)

• Copious lavage of the area, removing identifiable particles (which should be placed in water to prevent further combustion), and covering the area with saline-soaked gauze to prevent further combustion.

• Use of a Wood lamp in a darkened resuscitation suite or operating room may help identify WP particles in the wound.

• Rinse the contaminated burn with copper sulfate solution 1%, remove WP particles, and then use copious saline lavage to rinse off the copper sulfate.

• Copper sulfate combines with phosphorous particles to create a blue-black cupric phosphide coating. This impedes further WP combustion and makes particles easier to find.

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White phosphorus burns (2)

• Never apply copper sulfate as a dressing. Excess copper sulfate absorption can cause intravascular hemolysis and renal failure.

• WP injury can lead to hypokalemia and hyperphosphatemiawith ECG changes, cardiac arrhythmias, and death. Place the patient on a cardiac monitor and closely track serum calcium levels. Intravenous (IV) calcium may be required.

• Moistened face masks and good ventilation help protect patients and medical personnel from the pulmonary effects of phosphorous pentoxide gas.

• Naturally, avoid the use of flammable anesthetic agents and excessive oxygen around WP

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Administration of multiple-casualty

event

• Analysis of blast incidents indicates that "upside-down" triage is common; less injured patients typically arrive at the hospital, via ambulance or private vehicle, before the most severely injured victims

• First, peri-incident intensive care management (‘forward deployment’) and

• second, maintaining a ‘chain of command’ with efficient triage

• Patient identification, tracking and documentation

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In the ER

• Senior most trauma surgeon take the lead and

should define prorities for access to OT

• Avoid heroic procedures compromising

delivery of efficient care to the salvageable

victims

• Risk of undertriage, so repeated assessment

should be performed

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Control and coordination:

Accordion approach

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Challenges

• Many hours and sometimes days are requiredfor the situation to stabilize and eventuallynormalize

• Treating teams are physically and emotionallyexhausted from the continuous workload, especially when repeat attacks occur withindays;

• Repeated reassessment by the treating teams and SIC to ascertain that all patients receiveoptimal care is fundamental.

• In these circumstances, a strong personalcommitment by the treating teams and SIC ispivotal to success.