Be prepared to provide care for MWDs exposed to bomb blasts and other explosions. Blast injuries may be subtle or occult for several days and MWDs may appear stable on initial evaluation. Blast injuries can also cause wounds, ranging from mild to severe. For significant wounds that require long-term therapy, refer to the K9 Wound Management CPG.

BLAST INJURY MECHANISMS1-4

Blasts produce injury through:

- Primary effects of the blast overpressure wave.
- Secondary injury due to penetrating objects displaced by the explosion.
- Tertiary injury due to MWDs physically being displaced into objects.
- Quaternary injury due to complications resulting from any combination of the above or injuries unrelated to those mechanisms.

Primary blast lung injury (PBLI) caused by exposure to high-intensity pressure waves from explosions is associated with pulmonary parenchymal tissue injury and severe ventilation insufficiency in humans.1 Research investigating the transmission mechanism of pressure on the thorax showed that the apex of the lungs received the largest stress in a blast.3 PBLI patients are characterized by diffuse intra-alveolar destruction that has the potential to deteriorate into acute respiratory distress syndrome with high mortality.2

INITIAL MANAGEMENT

The approach to blast-injured MWDs is the same as for any other type of trauma. Focus on life-threatening problems first, followed by targeted support based on exam findings with emphasis on a detailed secondary evaluation and follow on care as needed once the patient is stabilized.

During initial care, focus on the life-threatening injuries caused from blasts:

- Massive hemorrhage from traumatic amputations, junctional hemorrhage, or hemoperitoneum
- Respiratory distress from an airway obstruction, pulmonary contusions, pneumothorax or hemothorax
- Shock secondary to air embolism or hypovolemia
- CNS trauma such as head trauma or spinal cord injury that could lead to spinal shock

Tympanic membrane (TM) rupture is a minor standalone injury but is typically suggestive of a more severe systemic injury. Patients with TM rupture should be observed for development of other injuries.3,4 Based on data from humans exposed to blasts, the absence of TM rupture does not exclude potentially life-threatening internal injuries.4

Many injuries from blasts may not manifest for several hours, including pulmonary contusions, pneumothorax, behavioral or neurological changes due to head trauma and bowel hemorrhage with or without perforation. Perform diagnostics based on physical examination findings and clinical presentation. When available, diagnostics should include point of care ultrasound exam, laboratory analysis (i.e., blood gas [venous or arterial], electrolytes, serum lactate), blood pressure and pulse oximetry measurements, electrocardiogram, Modified Glasgow Coma Scale, and thoracic and/or abdominal radiographs. These diagnostics should be performed serially to detect early signs of impending decompensation.

Any MWD exposed to a blast should be evacuated to a veterinary facility as soon as possible for detailed evaluation and observation. Considerations for stabilization and interventional therapy include oxygen therapy, judicious use of IV fluids, analgesic medications, needle decompression and/or chest tubes, sedation, intubation, mechanical or manual ventilation, and hyperosmotic therapy. Antibiotics may be needed if there are penetrating injuries from shrapnel or if there is evidence of ruptured abdominal contents. Therapies should be chosen based on clinical assessment of the patient. If evacuation is not possible or is delayed, hospitalize the MWD for 12-24 hours for close observation or longer if new clinical signs develop or present signs worsen.