Blast injury

Background

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

• Injuries to organs with air-fluid interfaces (spalling effect)
  • TMs
  • Alveoli
  • GI tract
• Military - young healthy soldiers with body armor reducing thoracic/abdominal injuries
• Civilian - children to elderly, higher rates of penetrating thoracic/abdominal injury
• 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

Clinical Features

• Penetrating and blunt injuries, burns, amputations
• Markers of severe blast injury
  • > 10% TBSA burn
  • Skull, facial fx
  • Penetrating injury to head or thorax
  • Traumatic amputations
• Primary blast injuries most likely to cause pulmonary, acoustic/head, thoracic trauma
  • Pulmonary is most common fatal PBI
    • Pulmonary contusion
    • Pneumomediastinum due to alveolar rupture - PTX, subQ emphysema, pneumopericardium, pneumoretroperitoneum, pneumoperitoneum, air embolus
    • Thrombosis, DIC, ARDS
  • Acoustic/head
    • 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 - immediate effects
    • CV collapse (within seconds)
    • Decreased BP due to impaired reflex that increases SVR
• Transmission of disease due to penetrating trauma is rare but possible with HIV, HCV, HBV

Workup

• 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

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.