BLAST INJURIES:

the Anesthesia Provider’s

Perspective

Linda E. Pelinka, MD, PhDMedical University of Viennaand Ludwig Boltzmann Institute

for Experimental & Clinical TraumatologyVienna, Austria, European Union

TRAUMATRAUMA

Blast Injuries in the USTexas 1947: Ammonium nitrate explosion

in a ship carrying cargo of hemp, 500 killed

Texas1989: Petroleum plant 23 killed,

130 injured (mainly males aged 25-44)

secondary injuries 2 miles

away

NYC 1993: WTC terrorist bomb 6 killed, 1042

injured

Oklahoma 1995: AP Murrah building

truck bomb, 167 killed (19 children)

„The explosion of a terrorist bomb in the garage of the World Trade Center resulted in 6 deaths...

Wightman JM and Gladish SL: Explosions and Blast Injuries. Ann Emerg Med, June 2001

...but thousands could have been killed, had one tower been toppled into the other as alledgedly intended.“

BASICS what, why and how

CATEGORIES Primary, secondary, tertiary and quarternary injuries, diagnosis and therapy

SPECIFIC ORGAN INJURIES Lung, gut, ear, brain, extremities diagnosis and therapy

BASICS

what, why and how

What is a blast?

Release of energy

Chemical conversion

of liquid or solid

to gas

What causes a blast?PROPELLANTS: slower energy release

DEFLAGRATION (chemical

burning) Gunpowder

*Psi pounds per square inch

EXPLOSIVES: instant energy release

DETONATION (causes high pressure of

about 4 million psi*)

High energy blast wave

= shock wave

TNT Trinitrotoluene

Composition C4 Cyclo-

trimethylene-trinitramine

What is a blast wave ?SHOCK WAVE

Sudden OVERPRESSURE of medium where blast takes place

injury from sudden overpressure and thermal energy, related to magnitude and duration of blastLong duration blast wave: nuclear detonation

Phases of a Blast

1. Very short phase: increasing pressure

2. Longer phase: decreasing-negative pressure

3. Short phase of slightly positive pressure

Massive movement of air: BLAST WIND

BLAST WIND

Strong enough to destroy buildings

145 – 800 mph

Pressure differential 5-15 psi (pounds/sq. inch)

Magnified 2-20 fold by corridors, alleys,

confined spaces (corners!)

Leading edge: blast front (highly pressurized,

superheated molecules, supersonic speed 15000 ft/sec)

Mechanisms of primary blast injury

SPALLATION at liquid-gas interfaces (bowel injuries)

IMPLOSION / RE-EXPANSION hollow

structures („crushed egg-shell fx“ of mid-face)

IRREVERSIBLE WORK by pressure differential

„Aluminum can concept“: Damage done when

stress = tensile strength of compressed tissue

ACCELERATION / DECELERATION

of organs relative to their fixation points

Less compression

and visible damage

to solid organs

with homogenous densities

(liver, spleen, tongue, eye)

CATEGORIES

Primary,

secondary, tertiary and

quarternary injuries, diagnosis and

therapy

QUATERNARY

BURNS (HOT GAS, SECONDARY FIRE)

INHALATION (DUST, SMOKE)

CRUSH (STRUCURES COLLAPSING)

Expected injury to unprotected victims, relative distance from a blast in open air

0

50

100

Closest Farthest

Total body disruption

Burns

Toxic inhalation

Traumatic amputation

PBI of lung and bowel

Tertiary blast injury

PBI of ear

Secondary blast injury0

50

100

Closest Farthest

Total body disruption

Burns

Toxic inhalation

Traumatic amputation

PBI of lung and bowel

Tertiary blast injury

PBI of ear

Secondary blast injury

PBI primary blast injury

Primary Blast Injury

Injury almost exclusively to

tissues of inhomogenous densities

(hollow, gas containing)

Cause: direct effect of blast wave on

victim (energy transfer)

Secondary Blast Injury

Cause: propelled debris which hits victim

Treat same as any

other blunt or penetrating injury

Beslan, Chechnia

September 3rd, 2004

Tertiary Blast Injury

Treatment same as for penetrating or

blunt trauma (fx, crush injuries,

amputations)

Cause: Victim impaled or

propelled against hard surface

Flash burns

superficial skin burns by heat of explosion

Methemoglobinemia

poisoning by potassium perchlorate (ammo)

Acute septicemic meloidosis

inhalation of contaminated soil

Psychological sequelae

Quaternary Blast Injuries

Miscellaneous collection of other mechanisms

Explosive munitions account for over 50%

of all wounds sustained in military combat.

The proportion of civilian casualties due to

explosives is increasing as well.

Mortality associated with use of weapons in armed conflicts, wartime atrocities, and civilian mass shootings

Coupland, RM and Meddings, DR: BMJ 319, 407–410; 1999.

Explosive Devices

CONVENTIONAL WEAPONS(Grenades, bombs, rockets)Multiple fragmentsSec. blast injuryPenetrating injury

ANTIPERSONNEL MINES(developing countries)Traumatic amputationDetonated by only 10 lbs pressure2000 victims every month (children)

ENHANCED-BLAST MUNITIONS(fuel-air explosives)Designed to kill by primary blast

TERRORIST DEVICES(few to hundreds of pounds of explosives)Secondary and Tertiary blast injury

Terrorist Devices

TRUCK BOMBS > 80 lbsDetonation creates secondary missiles from body of truckPenetrating injury, gross disruption

Designed toDisrupt passing vehiclesDisplace vehiclesEject victimsCause gross disruption

BARE CHARGES > 20 lbsRemote detonation (radio, wire)Primary blast injurySecondary fragments of metal and debris

CAR BOMBS2-6 lbs of commercial explosiveUnder car beneath driver´s seatTraumatic lower limb amputationSecondary fragments of metal

Velocity of Explosives

Initial velocity 1800m/sec

Rapid deceleration due to aerodynamic drag

(irregular projectile shape, no streamlining

like bullet through rifle barrel)

Survivors struck at velocity < 600m/sec

Shimmy effect: tumbling within tissue

Additional damage by environmental debris

Tolerance to Blast Wave in Air

standing worse than prone enclosed space worse than open

(multiple reflections)

radius of effect < radius of projectiles

more damage if blast wave reflected

by surfaces

Tolerance to Blast Wave in Water

tension wave (cut-off wave) reflected by surface

attenuates water blast wave closer to the surface

augments water blast wave in greater depth

more damage to deeper body regionsSafer floating than treading water

radius of effect > radius of projectileswater inhibits movement of projectiles

Tolerance to Blast Wave

Repeated blastsEffects cumulative (particularly airway: loss

of cilia, epithelial flattening, stripping, bleeding) sub-threshold blasts can result in injury if following close to previous blast

Effect decreases with distanceBlast wave travels further and

Lethal radius is 3x greater in water (vs air)

Shear wave

Stress w

ave

Longitudinal (like sound wave)Short durationHigh velocity (175 mph)Microvascular injuriesAlso affects hollow structuresMay cause limb avulsions

TransverseLong durationLow velocity (50 mph)

Deformation of body wallAsynchronous movementTearing from attachments

Multiple sequential posttraumatic aneurysms following high-energy

injuries

• 15 year-old boy

• Land mine in Lebanon

• Multiple long bone fx (external fixation)

• Lacerated right ant. tibial artery (grafted)

• 20 days later: pseudoaneurysm ulnar artery

• 34 days later: pseudoaneurysm peroneal artery with

a-v fistula (fluoroscopically controlled embolization and placement of stents)

Freiman S et al, J Orthop Trauma 2002

Primary Blast InjuryHas a patient been injured by a blast?

When to suspect:

Type of explosion

Medium of blast (air/water)

Number of blasts and time between

blasts

Victim’s location & position to blast

Enclosed area or barrier (reflected wave)

Activity after blast (risk of air embolism)

Ruptured tympanic membrane

Primary Blast Injury

Lung: most common cause of

early morbidity and mortality

Ear: most sensitive part of body

Bowel: most common cause of

delayed morbidity and mortality

SPECIFIC ORGAN INJURIES

Lung,

gut, ear, brain, extremities

diagnosis and therapy

Blast Lung

Pathophysiology

Ventilation – perfusion mismatch

Increased shunt

Decreased compliance

Increased work of breathing

Blast Lung

Signs

Tachypnoea

Cyanosis

Reduced breath sounds

Dull percussion sounds

Coarse crepitations

Subcutaeous emphysema

Retrosernal crunch (pneumo mediastinum)

Symptoms

Dyspnoa

(“can you count to 10 in a single breath?”)

Cough (dry-frothy)

Hemoptysis

Retrosternal pain

Caused by blast wave against chest wall – not through oropharynx and trachea

Blast Lung

Pathology and FindingsAlveolar septa torn

Hemorrhage

Laceration

Predeliction for

• Mediastinum

• Costo-phrenic angles

“Rib markings”

Pneumothorax

Pneumomediastinum

Subpleural cysts

Interstitial emphysema

Subcut. emphysema

Alveolo-venous fistulae

Air embolism

Pulmonary edema

Pulmonary contusions

Blast Lung

acute cardiovascular reflex triad

transmitted by the vagal nerve APNOEA

BRADYCARDIA

HYPOTENSIONRJ Guy, J Trauma 1998

Open-air blast in Beirut

0.6% of initial survivors had blast lung.

Confined-space blast in Jerusalem

35% of initial survivors had blast lung.

Blast Lung

Frykberg ER et al: The 1983 Beirut Airport terrorist bombing. Ann Surg 1989

Airway maintanance, C-spine control

Decompression of pneumothorax

Prophylactic chest drains

Breathing spontaneous if possible

High flow oxygen (15 L/min)

Blast Lung Management 1similar to that of lung contusion

If intubation is unavoidable

Unilateral lung ventilation, high

frequency ventilation, Extra-Corporeal

Membrane Oxygenation (ECMO)

Low tidal volume (peak pressure <30)

Reversion to spont. breathing ASAP

Beware of AAE (anesthesia, aircraft)

Blast Lung Management 2similar to that of lung contusion

AAC acute air embolism

Localization of massive hemoptysis

left lung right lung

Bleeding from

90° counter-clockwisewithout head rotationfor left lung

Alternatives:Univent tubeDouble lumen tube

Blast Injury to the Ear Symptoms

Hearing loss, high-pitched tinnitus

common initially, usually improves

Pain temporary, may last for weeks

Dizziness rare,

usually post-concussive

Bleeding

Blast Injury to the Ear Findings

Outside-in tympanic membrane rupture

in 70% of patients

Foreign material in ear

Cholesteatoma by implanted

keratinizing squamous cells

Ossicular injury

dislocation, fracture,

avascular necrosis

12 patients required treatment for ear

injuries3 of these patients had perforated ear

drums with persistent loss of hearing9 patients had short term loss of hearing

and tinnitus (4 hrs - 4 wks)None had balance problems

Blast Injury to the Ear: The London Bridge Incident

Walsh RM et al, J Accident & Emergency Med 1995

Treatment of Blast Injury to the Ear

85% of peforations heal spontaneously

Surgery (grafting) for large perforations

(>80% of surface area)

No need for immediate surgery (<1yr)

No need for prophylactic antibiotics

Long term review for cholesteatoma

Blast Injury to the Bowel

Combined intra-abdominal stress

and shear waves:Hematoma & tear of the mesentery & bowel Immediate rupture of the bowelStretching, ischemia, transmural weakening Late transmural necrosis – late rupture – septic MOFDetection may be difficult (silent for days, delayed rupture)

Blast Injury to the Bowel

Examination

Delayed diagnostic peritoneal lavage

probably most sensitive

CT and ultrasound unreliableTreatment

Abdominal exploration and repairBeware of risk of air embolism in

patient under general anesthesia

Blast Injury to the Bowel

Signs and symptomsNausea and vomitingHematemesis (rare)Rectal painTesticular painAbdominal tenderness, guardingAbsent bowel soundsHypovolemia

Blast Injury to the Bowel

Signs and symptomsNausea and vomitingHematemesis (rare)Rectal painTesticular painAbdominal tenderness, guardingAbsent bowel soundsHypovolemia

Blast–induced neurotrauma: A myth becomes reality.

In the past, research has focused on blast

injuries to gas-containing organs (lung, ear,

gastrointestinal tract), perhaps because the

brain was believed to be protected by the skull.

Cernak I, Presented at the 7th International Neurotrauma Symposium.

Medimond International Proceedings, Bologna, Italy, 2004.

Traumatic brain injury in the war zone.

More recent research indicates that TBI is a

common consequence of blast injury. TBI

accounts for a larger proportion of casualties

among soldiers surviving wounds sustained

in combat in Iraq and Afghanistan than in

previous conflicts.

Okie, S. N. Engl. J. Med. 352, 2043–2047; 2005.

Ultrastructural and functional characteristics of blast injury-

induced neurotrauma.

Reactive gliosis and neuronal swelling and

cytoplasmic vacuolation were observed in the

hippocampus of rats subjected to thoracic blast

injury even if the head was protected.

Cernak I et al. J Trauma 50, 695–706; 2001.

Cognitive deficits following blast

injury-induced neurotrauma:

possible involvement of nitric oxide.

Cognitive impairment and oxidative

stress also were observed after blast

injury in rats.

Cernak I et al. Brain Inj. 15, 593–612; 2001.

Blast-Induced Brain Injury and Posttraumatic Hypotension and

Hypoxemia

Hemorrhage accounted for approximately 50% of

combat deaths, and the lungs are one of the primary

organs damaged by blast overpressure. Thus, it is

likely that blast-induced lung injury and/or

hemorrhage leads to hypotensive and hypoxemic

secondary brain injury in a significant number of

combatants exposed to blast overpressure injury.

Dewitt DS and Prough DS. J Neurotrauma 2008

Blast-Induced Brain Injury and Posttraumatic Hypotension and

Hypoxemia

Unfortunately, the paucity of reproducible animal

models of blast injury has limited research on the

pathophysiology of blast injury and many important

features have not been investigated: Cerebral blood

flow, cerebral vascular reactivity to blast-induced

brain injury, effects of hemorrhagic or hypoxemic

posttraumatic insults on the blast-injured CNS.

Dewitt DS and Prough DS. J Neurotrauma 2008

Blast-Induced Brain Injury and Posttraumatic Hypotension and

Hypoxemia

Reactive oxygen species (ROS) are

produced by TBI. Superoxide radicals

combine with nitric oxide, another ROS

produced by blast injury, to form peroxy-

nitrite, a powerful oxidant that impairs

cerebral vascular responses.

Dewitt DS and Prough DS. J Neurotrauma 2008

ICP

CBV CPP

CBF

SECONDARY BRAIN DAMAGEVICIOUS CYCLE

AUTOREGULATION

Functional ImpairmentsPseudoanurysmsIntracerebral hemorrhage & vasospasmIncreased BBB permeability

edemaDiffuse axonal damage

impaired information processingRegional malperfusion

motor/sensory malfunctionCognitive deficits

retro/anterograde amnesia, confusion, indecisiveness Ropper A. N Engl J Med 2011; 364/22:2156-57.

Surgical Team’s experience in

Operation Iraqi Freedom.

Improvements in body armor, transport

and battlefield surgical care have all

contributed to increased survival.

Patel TH et al.J Trauma 57, 201–207; 2004.

Musculoskeletal Blast Injury

Surgical debridement

Excision of non-viable tissue

Drainage

Delayed closure

Most common injury in modern warfare

Secondary injury (debris projectiles)

Chitosan-based hemostatic dressing: experience in current combat.

Hemostatic dressings, bandages or pads filledwith substances that promote clotting, havebeen very effective in reducing hemorrhage.bandages containing chitosan, a carbohydrateDerived from chitin, were 100% successful instopping or reducing hemorrhage from externalwounds in Operation Iraqi Freedom.

Wedmore I, Holcomb JB et al. J Trauma 60, 655–658; 2006.

Debris propelled upward along

tissue planes

Compartment

injury

Contamination

Sepsis

Potentially Fatal Traumatic Amputation

Blast Wave-induced Fracture

Contaminated with bacteria

High risk of infection

Tetanus prophylaxis ASAP

Antibiotic prophylaxis ASAP

Major threats: Gas gangrene, Pseudomonas

Blast Injury and Air Embolism Main cause of immediate and early death

Signs and symptoms depend on vascular bed affected

Signs and symptoms• EKG: Arrhythmia, ischemia• Somnolence, headache, • Motor and/or sensory loss• Vertigo, ataxia• Seizures• Facial or tongue blanching• Transient blindness

Treatment of Air EmbolismAvoid/treat low vascular pressure

Avoid high airway pressure

Avoid head-down position

Administer oxygen

Hyperbaric oxygen therapy ASAP

e.g. after hemorrhage

e.g. resuscitation with PPV

increases intra-cranial pressurepromotes embolism to coronary vessels

reduces volume of bubblesimproves blood flow to tissues

Problems following Blast Injury

Combination: primary, secondary,

tertiary, quaternary

Combination of chemical and biological

injury

Toxic gas inhalation

TAKE HOME

MESSAGES

AIRWAYMentally altered

Intubation to safeguard airway

Sponteneous breathing if possible

Hemoptysis

Unilateral ventilation of less injured lung

BREATHINGLung contusion

100% oxygen, PEEP+PPV if necessary

Unilateral ventilation of better lung avoids

barotrauma in compliance mismatch

Pneumothorax

Additional chest drains

Hypovolemic shock Normalize pre-load to avoid AAE

As much fluid as necessary

As little fluid as possible

Cardiogenic shock

Coronary AAE semi/left-lateral decubitus position

hyperbaric oxygen

CIRCULATION

CONSIDER PRIMARY INJURY IN ALL BLAST

VICTIMSLUNG INJURY presents early

Exclude before general anesthesia

and air transportABDOMINAL INJURY presents late

May be silent until sepsis is advancedEAR INJURY is easily overlooked

Source of significant morbidity

and litigation

Blast - induced Air Embolism

main cause of early death