Traumatic thoracic injuries are prevalent in small animals, particularly in dogs.
Etiology of thoracic trauma:
- motor vehicular accidents (blunt trauma)
- bite wounds (penetrating trauma)
- less common mechanisms include
o gunshot wounds
o knife / stab wounds
o other penetrating wounds (e.g. impaling)
o being kicked by a larger animal (horse/cow); and
o high-rise syndrome.
Injuries may range from mild to life threatening.
Approach to the trauma patient:
Specific sequelae of thoracic trauma include pneumothorax, pulmonary contusions, hemothorax, rib fractures, flail chest, diaphragmatic hernia and cardiac arrhythmias. These are briefly discussed below.
- initial evaluation should concentrate on the major body systems (cardiovascular, lungs, brain) since a patient with significant thoracic trauma frequently has other serious and life-threatening injuries
- all trauma patients should be immediately triaged to the treatment room
- an IV catheter should be placed immediately and samples collected for determination of a packed cell volume, total solids, glucose and BUN (or a complete point of care profile such as a NOVA or i-STAT)
- supplemental oxygen should be administered if any signs of respiratory distress are present
- thoracocentesis may be performed if there is evidence of pneumothorax based on initial assessment
- intravenous fluids should be given if shock is present
- analgesia should be administered as needed
- after the patient's condition has stabilized, further testing may be performed as indicated.
Pneumothorax refers to the development of free air within the pleural space. Air enters the pleural space either from the outside via penetrating injuries or secondary to leakage from damaged pulmonary parenchyma.
- Auscultation and observation of respiratory pattern
o Inappropriately quiet lung sounds for degree of respiratory distress
o But can be misleading of respiratory sounds are louder than average associated with concurrent contusions etc.
o Restrictive breathing pattern (short shallow breaths)
- TFAST = thoracic focused assessment with sonography for trauma:
o Absence of the glide sign suggests pneumothorax (i.e. lack of the normal dynamic interface between lung margins gliding along the thoracic wall)
o Refer to Lisciandro et al. JVECC 18(3) 2008, p258-269 for complete description of the standard 4 point TFAST technique. These authors documented sensitivity = 78.1%, specificity = 93.4% and overall accuracy = 90% of TFAST relative to thoracic radiographs for the diagnosis of pneumothorax
- Thoracic radiographs:
o Considered the mainstay of diagnosis
- Diagnostic thoracocentesis:
o Often attempted based on clinical suspicion in animals with respiratory distress deemed too unstable for radiography, or following TFAST diagnosis of pneumothorax without radiographs
- Therapeutic thoracocentesis:
o ~ 25-30 ml/kg of air generally needs to be removed to provide significant improvement to respiratory status.
- Thoracostomy tube placement with intermittent or continuous chest drainage
o Occasionally required
o Indicated if ≥ 3 needle thoracocentesis procedures are required in <12- 18 hours or if no end-point is reached during thoracocentesis