Blast Injury

Blast injuries result from the complex pressure wave generated by an explosion. Air-filled organs (e.g. ear, lung, and gastrointestinal tract) and organs surrounded by fluid-filled cavities (e.g. brain and spinal cord) are particularly susceptible to primary blast injury. The pressure wave dissipates quickly, causing the greatest risk of injury to those closest to the explosion. Injuries can also occur by other mechanisms due to a blast, e.g. impact from blast debris, being physically thrown, burns and inhalation of gases.

Although terrorism is an ever increasing concern, most blast injuries are caused by accidents such as gas explosions. The management will often involve implementation of the local major incident plan. Blast injuries are divided into 4 categories:

• A primary blast injury is caused by the direct effect of blast overpressure on tissue. The injury almost always affects air-filled structures such as the lung, ear, and gastrointestinal tract.¹
• A secondary blast injury is caused by people being hit by flying objects.
• A tertiary blast injury is caused by high-energy explosions and occurs when people fly through the air and strike other objects.
• Miscellaneous blast-related injuries include all other injuries caused by explosions, e.g. due to fire or collapse of buildings.

Frequency depends on both the political stability of the region, e.g. terrorism, and local factors such as occupational health and safety priorities.

• Lungs may show evidence of pulmonary trauma and pneumothorax. Wheezing may be due to pulmonary contusion, inhalation of irritant gasses or dusts, pulmonary oedema or adult respiratory distress syndrome (ARDS).
• Rupture of tympanic membrane may but not always indicate additional more serious injury.²
• Abdominal injuries from explosions may not be immediately obvious and serial examinations are often required. Intestinal haematoma can take 12-36 hours to develop.

All investigations will be carried out by the within the emergency department but the following is a basic guide:

• Screening urinalysis to detect injury to the renal tract.
• If the explosion occurred in an enclosed space or was accompanied by fire, test carboxyhaemoglobin (carbon monoxide poisoning) and electrolytes to assess acid-base status.
• For major trauma, baseline haemoglobin, cross-match and screen for disseminated intravascular coagulation.
• If significant crush injury, compartment syndrome, or severe burns, rhabdomyolysis may cause hyperkalaemia and myoglobinuric renal failure.
• Burns from military white phosphorous munitions may cause hypocalcaemia and hyperphosphataemia. White phosphorus is a widely used component of military munitions, including hand grenades.
• Chest x-rays are required for all those who have been exposed to high-pressure injury.
• If significant abdominal pain, abdominal x-ray (erect and supine) or abdominal CT to detect pneumoperitoneum from bowel rupture.

See also Trauma Assessment and Resuscitation.

• If there is any question of radiation or chemical contamination, decontamination of patients and equipment will be required.
• There will inevitably be huge emotional as well as physical stress. Psychological help will be required from the outset and a calm, organised, supportive and caring approach to management of people involved in the accident is essential.

Drugs

• Life support, including intravenous fluids and blood transfusions may well be required at the site of the accident.
• Specific treatments may also need to be considered.
• Cyanide poisoning:
  • Consider cyanide poisoning in patients exposed to combustion in an enclosed space.
  • Cyanide is produced by incomplete combustion of plastics.
  • Treatment for cyanide poisoning should be started for significantly ill patients while awaiting confirmatory test results.
  • Sodium thiosulfate and hydroxocobalamin are safe and appropriate empirical therapy.

• Mortality rates vary widely.
• Mortality is increased when explosions occur in closed or confined spaces.³
• Tympanic membrane rupture indicates that a high-pressure wave was present and may be associated with more severe organ injury.