Blast injury

Background

• Primary blast wave increased in closed space - detonation in corner has potential to increase blast yield to 8x
• Recent enhanced-blast weapons (EBW) disperses gas before explosion - larger blast wave with lower pressure amplitude that diffuses around corners

Spalling Effect

Due to blast pressure forces, Injuries are to organs with air-fluid interfaces (spalling effect)

• TMs
• Alveoli
• GI tract

Situational Examples

• Military - young healthy soldiers with body armor reducing thoracic/abdominal injuries but significant groin and lower extremity injuries
• Civilian - children to elderly, higher rates of penetrating thoracic/abdominal injury

Injury Classifications

Classification

Blast Type	Injury Cause	Injuries	Example
Primary	Direct effect from shockwave	Sheer and stress forces	TM rupture, Ocular Injury, concussion, blast lung
Secondary	Penetrating trauma, amps, lacs
Tertiary	Blast propels body or large object into body	Crush injury and blunt trauma	Similar to MVC: Fractures, Pneumothorax, Hemopneumothorax
Quaternary	Environmental	Burns, Toxins, Weather
Quinary	Bodily absorption of contaminates	Hypermetabolic state

Effects based on blast pressure

Potential Injury	Pressure (PSI)	Structural Effects
Loss of balance/temporary ear damage	0.5-3 psi	Glass shatters; facade fails
Slight chance of eardrum rupture	5-6 psi	Cinderblock shatters; steel structures fail; containers collapse; utility poles fail
50% chance of eardrum rupture	15 psi	Structural failure of typical construction
Lung collapse/damage	30 psi	Reinforced construction failure
Fatal injuries	100 + psi*	Structural failure

Clinical Features

Pulmonary

• Blast lung is the most common fatal primary blast injury (PBI)
• Pulmonary contusion
• Pneumomediastinum due to alveolar rupture - pneumothorax, subcutaneous emphysema, pneumopericardium, pneumoretroperitoneum, pneumoperitoneum, air embolus
• Thrombosis, DIC, ARDS

EENT

• TM rupture most common - not a marker of PBI severity or prognosis
• Hemotympanum
• Ossicle injury
• Direct ophthalmic injury, foreign bodies, or ophthalmic artery air embolus

Thoracic

• Cardiovascular collapse (within seconds)
• Hypotensiondue to impaired reflex that increases SVR

Infectious Disease

• Transmission of disease due to penetrating trauma is rare but possible with HIV, HCV, HBV

Musculoskeletal

• Amputations
• Burns

Markers of severe blast injury

• > 10% TBSA burn
• Skull, facial fracture
• Penetrating injury to head or thorax
• Traumatic amputations

Differential Diagnosis

Mass casualty incident

• Radiation exposure (disaster)
• Dirty bomb
• Bioterrorism
• Chemical weapons
• Natural Disaster (e.g. Hurricane, Earthquake, Tornado, Tsunami, etc)
• Unintentional large-scale incident (e.g. building collapse, train derailment, etc)
• Major pandemic
• Explosions

Evaluation

• CXR, CT chest
• FAST, comprehensive CT
• Repeat clinical abdominal exams looking for peritonitis - X-rays, US, CT insensitive except in perforation
• Initial CT head may not be enough - may require MRI for DAI
• Labs
  • Consider carboxyhemoglobin and electrolytes
  • Screening UA for significant explosions
  • Burn labs (rhabdomyolysis, compartment syndrome, severe burns)
  • DIC labs (PT, aPTT, CBC, D-dimer, thrombin time, fibrinogen)
  • White phosphorous labs (hypocalcemia, hyperphosphatemia, LFTs)

Management

• pRBCs and FFP in 1:1 ratio with platelets for hemodynamically unstable patients
• TM rupture - initial treatment supportive and enough for 75% with spontaneous healing; operative repair may be necessary for others
• Operative exploration for peritonitis
• Air embolus (rare) - isolate air in apex of LV by placing patient in left decubitus, head down, feet up position

Disposition

• Ambulatory patient with normal TM evaluation at low risk for occult blast injury - discharge with precautions
• All others require admission

See Also

• Explosions

Video

Authors

Ross Donaldson