Thoracic trauma (Proceedings)

Traumatic injuries of the respiratory system are fairly common in the dog and cat. Most of these injuries can lead to life threatening complications. It is important that the veterinary clinician be familiar with the clinical signs associated with these injuries and be prepared for aggressive intervention when required. This paper will present some of the common traumatic injuries affecting the respiratory system, clinical signs and treatment for stabilization.

Airway trauma

Traumatic injuries of the airways can occur in both dogs and cats. These injuries may be secondary to blunt or penetrating trauma. Blunt trauma to the trachea or larynx can lead to hemorrhage or edema of the airway. In some cases this trauma can lead to secondary obstruction due to swelling of the airway mucosa and or hemorrhage. The most vulnerable portion of the airway system is the trachea. The cervical trachea is susceptible to crushing injuries, ballistic injuries and other penetrating injuries such as bite wounds.

Clinical signs associated with airway trauma include dyspnea and cyanosis. Subcutaneous emphysema is often present following the injury. The respiratory pattern may vary depending on the level of the disease ie extrathoracic versus intrathoracic. Additional diagnostic evaluation may include radiography, contrast radiography or tracheoscopy.

Emergency treatment of these cases includes oxygen supplementation and restoration of the airway. This may include tracheostomy and continued medical management or surgical repair in the case of tracheal disruption. Stabilization of other concurrent disorders such as shock and pneumothorax must also be a priority.

Flail chest

Flail chest is a specific injury that involves multiple rib fractures. Flail chest occurs when dorsal and ventral fractures occur in tow or more adjacent ribs. The sequel of these fractures is a free-floating section of the thoracic wall. This section of thoracic wall demonstrates paradoxical motion or "flailing". With this degree of thoracic trauma these pets are generally dyspneic. The dyspnea may be due to concurrent injury such as pneumothorax, hemothorax or pulmonary contusions and the pain associated with the trauma. These pets will benefit from the administration of oxygen and analgesics. Due to the risk of administering systemic analgesic agents that may adversely affect respiratory function local analgesia should be considered. Local infiltration with lidocaine and bupivacaine may be useful in these patients (1.5 mg/kg). Ventilatory support may also be required may be required depending on the severity of the injury and evaluation of ventilation.

Rib fractures not associated with flail chest should be treated in a similar manner. Restrictive bandages placed around the thorax are contraindicated in patients with rib fractures or flail chest.

Pulmonary contusions

Pulmonary contusions are a common finding in animals with thoracic trauma. This injury occurs after hemorrhage into the pulmonary parenchyma and alveoli. There may be concurrent disease such as pneumothorax and hemothorax. The diagnosis is often made after thorough physical examination, thoracic auscultation and review of thoracic radiographs. Negative thoracocentesis in a dyspneic pet should increase the clinical suspicion of the presence of pulmonary contusions. The clinical finding of hemoptysis is also indicative of pulmonary contusion. Thoracic radiographs may not reveal the full extent of injury during the acute assessment of the patient. Arterial blood gas analysis and pulse oximetry may be more sensitive tools for evaluation of these patients. The hypoxemia that is detected in these patients is generally due to ventilation perfusion mismatch and intrapulmonary shunting.

Cage rest and oxygen supplementation are the treatments of choice for pulmonary contusions. The use of antimicrobials and corticosteroids are controversial. The use of furosemide to treat pulmonary contusions in the unstable patient is contraindicated. Some clinicians have used bronchodilator therapy empirically for these cases, but bronchoconstriction is not part of the pathophysiology of this disease.

Pneumothorax

Pneumothorax or air in the pleural space is most commonly seen in dogs and cats secondary to trauma. Physical examination of these animals usually indicates a restrictive breathing pattern, which is characterized by rapid shallow breathing. Thoracic auscultation reveals dull or distant lung sounds. Thoracic percussion is often a useful tool and may be hyperresonant confirming the diagnosis. Thoracocentesis should be performed immediately and prior to thoracic radiographs if the animal is dyspneic.

Oxygen supplementation via face mask may be used in these patients prior to and during thoracocentesis. Thoracocentesis can be performed with the pet standing or in sternal or lateral recumbency. Thoracocentesis can be performed using a 60 cc syringe, fluid administration extension set and 20-22-gauge needle. Alternatively a transvenous catheter or butterfly catheter can be used. Thoracic radiographs may be useful but should not be performed until the patient is stabilized. If thoracocentesis continues to be productive, after several attempts, thoracic drain placement may be required. As with other thoracic injuries, remember that concurrent disease may be present. Oxygen supplementation is often beneficial.

Pleural effusion

Pleural effusion refers to the presence of some type of fluid in the pleural space. This is similar to another type of pleural space disease; pneumothorax which has already been discussed. The types of traumatic pleural effusion include hemothorax and chylothorax. The diagnosis of hemothorax is far more common than chylothorax in the trauma patient. The presence of fluid in the pleural space should be able to be detected on thoracic auscultation and percussion.

Similar to pneumothorax, thoracocentesis is an important component of diagnosis and therapy. Oxygen supplementation will be useful during the initial management of these cases. Fluid analysis should be performed as soon as possible to confirm the diagnosis. Imaging such as thoracic radiographs and ultrasound should be delayed until the patient is stable. If the effusion is refractory to therapy with thoracocentesis, thoracostomy tube placement must be considered.

Diaphragmatic hernia

Diaphragmatic hernia is another common traumatic injury in the dog and cat. Diagnosis is most commonly made after survey thoracic or abdominal radiographs. These animals are often not stable due to shock, pulmonary contusions and pain associated with the traumatic incident. The concurrent injuries should be treated and the patient stabilized prior to surgical intervention for repair of the diaphragm. Oxygen therapy may benefit these patients and thoracocentesis may be performed if pleural effusion or pneumothorax is present.

Summary

Traumatic injuries of the respiratory system often cause life-threatening complications in the dog and cat. It is therefore important for the veterinary clinician to rely on history, clinical signs and physical examination findings to triage these patients and provide efficient and effective care. In many cases supportive care including oxygen therapy, fluid therapy and analgesia will help stabilize these patients.

Suggested reading

Camps-Palau MA, Marks SL, Cornick JL. Small animal oxygen therapy. Compen for Cont Edu 21(7):587, 1999.

Crowe DT. Traumatic pulmonary contusions, hematomas, pseudocysts, and acute respiratory distress syndrome. Part I. An update. Compend Contin Educ Pract Vet 5(5):396– 401, 1983

Gibbons G. Respiratory Emergencies. In: Murtaugh RJ, Kaplan PM (eds). Veterinary Emergency and Critical Care Medicine. St. Louis, Mosby Year Book, 1992; 399-419.

.Hackner SG. Emergency management of traumatic pulmonary contusions. Compend Contin Educ Pract Vet 17(5):677– 686, 1995.