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 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 PBI
• Pulmonary contusions
• Pneumomediastinum due to alveolar rupture - PTX, subQ emphysema, pneumopericardium, pneumoretroperitoneum, pneumoperitoneum, air embolus
• Thrombosis, DIC, ARDS

ENT

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

Thoracic

• CV collapse (within seconds)
• Decreased BP due 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 fx
• Penetrating injury to head or thorax
• Traumatic amputations

Differential Diagnosis

Mass casualty incident

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

Diagnosis

• 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 HbCO 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)

Treatment

• pRBCs and FFP in 1:1 ratio with platelets for hemodynamically unstable pts
• TM rupture - initial Tx 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 pt in left decubitus, head down, feet up position

See Also

• Explosions

References

1. Pennardt A, Lavonas EJ, Danzl D, Talavera F, Levy DB, Halamka JD. Blast Injuries. eMedicine Medscape Review. Last updated Apr 21, 2014. http://emedicine.medscape.com/article/822587-overview#showall
2. Yeh DD, Schecter WP. Primary blast injuries - An updated concise review. World J Surg (2012). 36:966-972.
3. Ritenour AE, Baskin TW. Primary blast injury: Update on diagnosis and treatment. Crit Care Med 2008; 36[Suppl.]:S311-S317.