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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