Wound Ballistic Bomb & Blast Injury - · PDF fileOverpressure reflection At a surface, sound...
Transcript of Wound Ballistic Bomb & Blast Injury - · PDF fileOverpressure reflection At a surface, sound...
Wound Ballistic
Bomb & Blast Injury
Biophysics & Pathophysiology
Jim Ryan
WOUND BALLISTICS
The study of wounds caused by
penetrating missiles
Epidemiology - Civil
Incidence of GSW low in Europe
Pistols & shotguns
Increase in weapon range
Incidence of fragment wounds
Related to terrorism
Part of combined injury
GSW Right Shoulder
Typical Terrorist Wound Profile
Epidemiology - Military
Full range of weapons & systems
Fragment wounds predominate
Multiple wounds
Multiple systems
Part of combined injury
Multiple casualties
Military Assault Rifle Wound
Pre-formed Fragment Wounds
Basic Ballistics
Bullets
Low-energy Transfer (LeT)
High-energy Transfer (HeT)
Military
Jacketed
Civilian
Police
Hunting
The myth of Velocity
Kinetic energy = ½ mv²
Where m is mass
and v is velocity
Terrorist Fragments
High-energy Transfer (HeT)
High velocity bullets with retardation
High energy fragments
Shot gun
Solid slug
Close range
Wound Classification
Low-energy Transfer (HeT)
Low velocity (caveat)
Many hand guns
Perforating rifle bullets - <retardation
Stab wounds
Wound Classification
Mechanisms of Injury
Direct laceration & crushing
Cavitation (HeT)
Missile fragmentation / deformation
Contamination
Shock wave ??
Temporary Cavitation
1.Cadaver muscle
2.Indirect fractures
3.Opening of fascial
planes
4.Contamination
5.Fragmentation of the
missile
High-energy Transfer - Head
Hand Gun
High-energy Transfer - Abdomen
High-energy Transfer - Leg
Missile & bone fragmentation
Low-energy Transfer – Chest Assault Rifle
High-energy Transfer - Liver
Velocity – Energy irrelevant!
Multiple Fragments
Multiple hits
Multiple cavities
Clustering
Occult injury
Management
Management principles remain the
same
Do not Panic!
Summary
Treat the patient and wound,
not the weapon
Keep an open mind
Take a Short Break
An explosion is the phenomenon that
results from a sudden release in energy
Sources
1.Gunpowder or TNT
2.Chemical explosion
3.Pressurised steam in a boiler
4.Uncontrolled nuclear transformation
Explosions result in the sudden
release of energy. They form blast
waves (shock wave +blast wind)
and other physical phenomena
which may result in clinically
significant consequences
Significant Phenomena
1. Shock wave - overpressure
2. Blast wind – dynamic pressure
3. Disruption of the environment with generation of projectiles
4. Collapse of buildings – entrapment & crush
5. Thermal injury – flash & ignition
6. Inhalation of toxic fumes & smoke
Most damage caused by energised fragments
Simple physics of an explosion
Blast (wave) 2 elements:
– Shock wave
– Travels at >330m/s
– High overpressures
– Short duration
– Dynamic overpressure –
aka blast wind
– Moves things!
Heat from explosive
products
Shock wave
Edge of explosive products (Dynamic overpressure)
Bombs and explosions cause unique patterns of
injury seldom seen outside war and terrorism
The predominant post explosion injuries among
survivors involve standard penetrating and blunt
trauma
Blast Injuries: Variation in clinical consequences
Medium (air vs water)
Environment (open vs closed spaces)
297 Open space bombings v 93 bus bombings1
1 Leibovici J Trauma 1996
P<0.0001 4 18 Median ISS
P=0.00003 34.2% 77.5% Primary blast
injury
P<0.00001 7.8% 49% Mortality
SIGNIFICANCE OF
DIFFERENCE
OPEN AIR BOMB BUS BOMB
Overpressure reflection
At a surface, sound
pressure is doubled
For shock waves:
– overpressure at
surface may be up to 8
times incident
Reflection and
enhancement will lead to
very complex loading
Time, milliseconds
Ove
rpre
ssure
, kP
a
Atmospheric pressure
Initial shock wave
Shock reflections
Bomb blast injury
Consequences
Multisystem injury
Combined injury
Multiple casualties
Not for the novice
Blast Injuries: Types
Primary (caused by the blast shock wave)
Secondary (fragment acceleration – ballistic injury)
Tertiary (victim is thrown – disruption,disintegration)
Quaternary
– burns, smoke, chemicals
– toxins
– infection
– crush (collapsed buildings)
Primary Blast Injury:
Often absence of external injuries
Extensive parenchymal damage
– some immediate
– some delayed
Therefore, frequent underestimation and delayed
management of injuries
Primary effects – Clinical consequences
1.Blast lung - Acute lung injury (ARDS)
2.Pneumothorax, contusion
3.Bowel contusion/perforation
4.Ear injury
5.Other
Cardiac
CNS
Blast lung -
1.Rare in survivors
2.High index of
suspicion
3.Serial blood gases
4.Pulse oximetry
5.Ventilation - ITU
6.? steroids
Blast injury to bowel
Contusions to large and small
bowel
– occasional acute perforation Usually associated with primary lung
injury
Difficult to diagnose without
laporotomy
Risk of delayed perforation
Caused by shock wave (small)
and shear (large)
Bowel perforation
1.Rare in air blast
2.Common in water blast (water hammer)
3.High index of suspicion
4.Serial exams – CT, FAST, DPL
5.Contusion probably under-reported
Ear injury
1.Common
2.Under-reported
3.Deafness
4.Audiometry
5.Follow up
Other primary sequelae
1.Coronary artery air
embolism
2.Under-reported cause
of death
3.Also CNS air
embolism - stroke
Secondary effects – clinical consequences
1.Generation of fragments
- Primary
- Secondary
2.Penetrating ballistic injury
3.Multiple injuries & multi-system
4.Variable depth of penetration
5.Heavily contaminated
6.Commonest clinical problem
Fragment Injury
Tertiary effects – Clinical consequences
Blast wind
Displacement
- Environment
- The individual
Disruption
- Environment
- The individual
Other – Clinical Consequences
Crush Injury
Thermal
–Flash
– Ignition
– Inhalation
Psychological
–PTS Syndromes
–PTS Disorder
Management
1.ATLS Protocols
2.Penetrating injury predominates
3.Multiple systems
4.Need to prioritise-which injury first?
5.Need to understand underlying biophysics &
pathophysiology
Major Trauma
Multiple injuries
Multiple systems
Multiple victims
Lack of experience
Multi-Disciplinary
Multiple Injuries
Critical decision making
Priorities
Communication
‘Between two stools’
Ownership
Environment
Preparation
Pre-hospital
Transfer guidelines
Communication &
direction
Closest, appropriate
hospital
Preparation
In Hospital
Major incident plan
activated
Control room open
Triage team in place
Resus rooms manned
appropriately
Mobilisation of
resources & assets
Bombs & blast – common wound profiles
Interaction of blast waves with the body
Dynamic overpressure (gas flow)
– Flow shears tissue e.g. gross soft tissue injury
– Loads the body and body wall - displacement
– Avulse fractured limbs
– Burns from products
Primary Blast Injury:
Prediction of Severity?
Eardrum perforation as a marker of Pulmonary
Blast Injury? Israel 1999
Lab markers of severity of injury from blasts:
– IL-1
– TNF
– IL-6
– TxA2 Leukotriene
Bomb blast victim
What is this pathology ?
Summary
Treat the patient and wound,
not the weapon system
Keep an open mind & use
usual ATLS principles
Classification of blast injuries (1)
Primary - principally air containing organs
– Primary blast lung – 70psi
– Bowel injury
– Auditory – 2psi
– Some solid viscera
Secondary - wounds from fragments
– Penetrating - superficial to perforating
– Visceral injury from blunt impacts
Classification of blast injuries (2)
Tertiary
– Traumatic amputation of limbs
– Displacement of the body
– Tissue stripping by gas flow
Quaternary
– Crush injuries
– Burns
– Psychological
Quinternary
– Neurological – repeated TBI
– (Immuno-compromise)
DCR achieved by:
Aggressive approach to
– Hypovolaemia
– Hypotension
– Coagulopathy
– Hypothermia
– Acidosis
Near-patient diagnostics
Focussed abbreviated
surgery
Intensive/Critical Care
Dynamic overpressure (“Blast Wind”) Motion of explosive products
Associated with the shock wave at time of
detonation
– shock wave accelerates ahead very
quickly
Moves things due to gas flow
Gas flow (products)
Shock front (wave)
“War does not
determine who is right,
– Merely who is left”
Probability of Injury
Probability and type of trauma is related
to the casualty’s distance from the
epicenter of the detonation