Blast Injuries 

1. Physics of Explosion – Why Blast Injury is Unique

An explosion generates:

  1. Shock wave (overpressure wave)
  2. Blast wind
  3. Fragmentation
  4. Thermal energy
  5. Toxic gases


High-Order vs Low-Order Explosives

Feature

High-Order (e.g., TNT, RDX)

Low-Order (e.g., gunpowder)

Detonation velocity

Supersonic

Subsonic

Produces shock wave

Yes

No true shock wave

Causes primary blast injury

Yes

Rare

Causes fragmentation

Yes

Yes


2. Classification of Blast Injuries 

 Classification of Blast Injuries 

Type of Blast Injury

Mechanism

1️⃣ Primary Blast Injury (PBI)

Caused by overpressure shock wave from high-order explosive

2️⃣ Secondary Blast Injury

Caused by flying debris / shrapnel / fragments

3️⃣ Tertiary Blast Injury

Body is thrown against solid objectdue to blast wind

4️⃣ Quaternary Blast Injury

Other explosion-related effects (thermal & environmental)

5️⃣ Quinary Blast Injury

Hyperinflammatory response due to toxic additives (chemical/radiologic)



3. Primary Blast Injury 

 Blast Lung (Most Important for CCM)

Pathophysiology

  • Overpressure wave → alveolar rupture
  • Capillary disruption
  • Hemorrhage
  • Edema
  • Pneumothorax
  • Air embolism

It behaves like severe pulmonary contusion + ARDS


Clinical Features

  • Dyspnea
  • Hemoptysis
  • Hypoxia
  • Cyanosis
  • Subcutaneous emphysema
  • Tension pneumothorax

Symptoms may be delayed 6–48 hrs.


Imaging

CXR:

  • Bilateral patchy infiltrates
  • Butterfly pattern

CT:

  • Ground-glass opacities
  • Pneumatoceles
  • Air embolism


ICU Management 

Management similar to ARDS but with caveats.

Airway

  • Early intubation if hypoxic
  • Avoid excessive bagging (risk of air embolism)


Ventilation Strategy

  • Low tidal volume (6 ml/kg IBW)
  • Plateau pressure <30 cm H2O
  • Moderate PEEP
  • Avoid aggressive recruitment maneuvers

Why?
High airway pressure → worsens air leak


Pneumothorax Rule 

Insert chest tube BEFORE positive pressure ventilation if suspected pneumothorax.


Permissive Hypercapnia

Allowed unless:

  • TBI present
  • Severe acidosis


Prone Positioning

If severe ARDS (PaO2/FiO2 <150)


ECMO

Consider in refractory hypoxemia


 Air Embolism – Unique to Blast

Alveolar rupture → air enters pulmonary veins → cerebral or coronary embolism.

Clues:

  • Sudden neuro deficit
  • Cardiovascular collapse

Management:

  • 100% O2
  • Left lateral decubitus
  • Hyperbaric oxygen (if available)


4. Blast Tympanic Membrane Rupture

Most sensitive marker of primary blast exposure.

But: Absence does NOT rule out blast lung.

Symptoms:

  • Hearing loss
  • Tinnitus
  • Vertigo

Management:

  • Usually conservative
  • ENT referral


5. GI Blast Injury

Occurs due to pressure wave.

Common sites:

  • Ileum
  • Colon

May present late (24–72 hrs).

Features:

  • Abdominal pain
  • Peritonitis
  • Free air

High suspicion required.


6. Secondary Blast Injury

Penetrating trauma from:

  • Glass
  • Metal fragments
  • Bone fragments

Management:

  • ATLS protocol
  • Damage control surgery
  • Broad-spectrum antibiotics
  • Tetanus prophylaxis


7. Tertiary Blast Injury

Patient thrown → blunt trauma.

Common:

  • TBI
  • Long bone fractures
  • Spinal injuries

Always:
Assume cervical spine injury.


8. Quaternary Injury

Includes:

  • Burns
  • Inhalation injury
  • Crush injury
  • Compartment syndrome
  • Rhabdomyolysis


 Inhalation Injury

Suspect if:

  • Soot in airway
  • Singed hair
  • Hoarseness
  • Closed-space explosion

Treat:

  • Early intubation
  • Bronchoscopy
  • 100% O2
  • Consider CO poisoning


9. Hemodynamic Considerations

Blast victims may have:

  • Hypovolemia (hemorrhage)
  • Myocardial contusion
  • Neurogenic shock
  • Air embolism

Resuscitation:

  • Damage control resuscitation
  • Balanced transfusion (1:1:1)
  • Permissive hypotension (if no TBI)


10. Special Consideration: TBI + Blast Lung

Conflict:

TBI

Blast Lung

Avoid hypercapnia

Permissive hypercapnia

Avoid hypoxia

ARDS present

Maintain CPP

Low PEEP

Management becomes complex:

  • Tight PaCO2 control (35–40)
  • Careful PEEP titration
  • Multidisciplinary approach


11. Mass Casualty & Triage

In blast events:

Use:

  • START triage
  • Damage control strategy
  • Early transfer to trauma center

Immediate category:

  • Airway compromise
  • Tension pneumothorax
  • Massive hemorrhage