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VetVine Client Care

Posted On Jun 23, 2025

Updated On Jul 16, 2025

Hit By Car - Dyspneic Dog

Emergency & Critical Care

Case contributed by Melissa Holahan, DVM, DACVECC

"Lucky" is a 2 year-old male intact mixed breed dog that presented after sustaining vehicular trauma. On triage, this was his respiratory pattern:



How would you describe this respiratory pattern? What are the most likely differentials?

"Lucky" has a flail chest. A flail chest occurs when the costal support of a section of the thoracic wall has been lost due to multiple (minimum of two) fractures, dorsal and ventral, of at least two adjacent ribs. The section "flails" asynchronously with normal motion of the thorax during respiration and is characterized by paradoxic inward displacement during inhalation and outward displacement during exhalation.

Patients with a flail chest should be closely evaluated for concurrent thoracic trauma including pulmonary contusions (which can become more severe in the first 24-hours after trauma) and pneumothorax. Both of which should be considered present (esp. in vehicular trauma patients) until proven otherwise so they are not overlooked and therapy is not misdirected.

Alveolar and small airway rupture can also cause a pneumomediastinum that can progress to subcutaneous emphysema as the air migrates through fascial planes at the thoracic inlet. Air can also reach the subcutaneous tissues if the pleura and intercostal muscles are disrupted. Generally subcutaneous emphysema is not of major concern.

Upon full examination “Lucky” had sustained all of these injuries following vehicular trauma: flail chest, pneumothorax, pneumomediastinum and subcutaneous emphysema.

All of these injuries can be painful (esp. flail chest & subcutaneous emphysema). Therefore, pain management should be addressed as soon as possible (as part of the initial resuscitation). Pain impairs ventilation due to a reluctance to fully expand the thoracic wall. Splinting of the thorax in an effort to diminish pain contributes to hypoventilation, which results in hypoxemia, and pulmonary atelectasis.

My analgesic of choice for these patients initially is fentanyl, as many of these patients are not hemodynamically stable on presentation, may have underlying traumatic brain injury / neurologic dysfunction and are often dynamic patients. Fentanyl is useful as it is short acting, reversible and has minimal cardiopulmonary side effects. You can either use it briefly as a bolus or set up a quick CRI. 

Initial stabilization for "Lucky" included: fluid resuscitation, flow-by oxygen (transferred to oxygen cage once stable), pain management (fentanyl 2 mcg/kg bolus followed by a CRI), and therapeutic / diagnostic thoracocentesis on the less affected side.


Originally posted on March 31, 2014