blast injuries

Blast injuries:

primary-- cause solely by the blast overcompression on tissues. Air is easily compressible, but water is not. So, as a result, a primary blast injury will affect air-filled strictures, such ad the gastrointestinal tract, lungs, and ears.
secondary-- caused by an object thrown by the blast which strikes the patient
tertiary-- typical of high-energy explosions. The patient is thrown by the explosion and strikes another object
miscellaneous-- any other injuries

A rupture of the tympanic membrane indicates a high-pressure wave-- at least 6 psi, and may correlate with more dangerous internal injuries, especially to the lungs. If the TM is ruptured or torn, a CT (computed tomography) should be performed

Lungs should be checked for evidence of contusion and pneumothorax. Wheezing is usually due to inhaled irritants (gasses or dust) and/or pulmonary edema

Pulmonary barotrauma is the most commonly fatal primary blast injury. Includes: pulmonary contusion, systemic air embolism, thrombosis, lipoxygenation and intravascular coagulation (clotting). ARDS (adult respiratory distress syndrome) may indicate a direct lung injury

Acute gas embolism (AGE, a form of pulmonary barotrauma) most commonly will occur in the blood vessels of the brain or spinal cord. Resulting neurological symptoms are different from those of direct trauma, but require immediate attention

Intestinal barotrauma happens most often in cases of water explosions, usually affecting the colon

In most cases, the extent of acoustic trauma is the rupturing of the tympanic membrane. With high-energy explosions, the ossicles may be fractured or dislocated (a marker of more pressure injuries)

The most common tertiary blast injury are skull fractures and traumatic amputation of long bones (humerus, femur, etc.)

Miscellaneous blast injuries may include inhalation of toxins, exposure, radiation and burns (chemical or thermal). Incomplete combustion, dust inhalation and asbestos exposure may result in CO and CN poisoning. Crush injuries also happen with alarming frequency

Patients who have been exposed to a blast should have a screening urinalysis. If the explosion took place in an enclosed space, COHgb and electrolyte levels should be examined (for the serum bicarbonate and anion gap)

A difference between the measured and calculated O₂ levels may indicate CO poisoning (if there is doubt, apply a 100% oxygen mask until CO levels can be more accurately measured)

Cyanide (CN) is the product of the incomplete combustion of plastics, often found in combination with CO poisoning

If severe burns are observed, watch for rhabdomyolysis and the resulting hyperkalemia and myoglobinuric renal failure. Specifically, if the blast is from a military white phosphorus munition, there is a high rick of hypocalcemia and hyperphosphatemia. IV calcium may be necessary

Abdominal CT's may reveal intestinal hematoma. Also watch for high abdominal pain and vomiting

WP (white phosphorus, see above) is a metal, found most often in grenades, that ignites on contact with the air. If this is the cause of the blast trauma, identifiable particles and fragments should be removed and stored in water or oil to prevent further combustion. Rinse with a 1% copper sulfate, which creates, in contact with the WP, a blue-black cupric phophide coating, making the particles easier to find and preventing them from further combustion. Excessively used copper sulfate may cause intravascular hemolysis, acute renal failure and even death. Needless to say, copper sulfate should never be applied as a dressing and thoroughly washed out after use

Most TM tears or punctures will heal spontaneously. Complications may arise from ossicle damage, cholesteatoma or perilymphatic fistulae. About 33% (one third) of patients suffer permanent hearing loss