Introduction

Animals with thoracic trauma frequently present in small animal clinics and should always be treated as an emergency. Trauma is often as a result of traffic accidents (11-40% of cases 1) and many patients will also have fractures (20-60% of cases 2 3). Other than traffic accidents and other blunt trauma such as kicks, the most common etiologies are animal bites and penetrating injuries from impaling, knives, firearms, etc. However many patients with thoracic injuries may not show signs and/or lesions at the time of admission, although signs can appear and progress 24-48 hours following the incident.

Thoracic trauma can be classified as being open (e.g., from knives, bites or bullets (Figure 1)) or closed (e.g., following falls, traffic accidents) in nature. 

In the event of severe or multiple injuries, it may be necessary to obtain the full medical history after or whilst the patient is being stabilized. A detailed history, including the time between the incident and presentation at the clinic, can offer important information. A complete and exhaustive physical examination is essential, paying special attention to the respiratory and cardiovascular systems. A detailed inspection of the thorax is mandatory, and it should be palpated, percussed and auscultated; if necessary the entire area should be shaved — especially when dealing with open injuries (Figure 2). The mucous membranes, capillary refill time, arterial pressure and mental state should all be assessed, and any neurologic/posture alterations noted. Initial supportive therapy should follow the ABC rule:

• Airway maintenance and oxygen therapy

• Breathing (respiratory/thoracic wall) support

• Cardiovascular and circulatory support

Hypoxia and hemorrhage are two of the main causes of death in the polytraumatized patient. If a patient presents in shock and there is no evidence of external bleeding, internal hemorrhage should be considered, and the abdomen and thorax should be thoroughly checked 4. 

Initial handling and stabilization

This article will focus on traumatic pneumothorax, hemothorax and lesions of the chest wall, but five key points to consider when initially assessing any patient subjected to thoracic trauma are as follows: 

1. Oxygen supplementation: this requires careful handling to minimize stress, and can be done either by mask (only on initial admission), chamber or nasal catheter.
2. Re-establish negative intrathoracic pressure: if an animal is dyspneic, bilateral thoracocentesis should be performed and any free air or fluid removed. Chest radiographs should then be obtained. If there is a penetrating wound the area should be shaved, cleaned and protected with a padded, non-compressive, hermetic dressing.
3. Hemodynamic stabilization: one (or two) intravenous catheters should be placed, a blood sample taken for analysis, and fluid therapy commenced. If necessary (e.g., severe hypotension) fluids should be administered by the intra-osseous route.
4. Multimodal pain management: pain control is very important and opioids are often first-choice on admission; a continuous IV infusion of morphine, lidocaine and ketamine (MLK) can also be very effective.
5. Broad-spectrum antibiotic therapy: drugs such as cefazolin or potentiated amoxicillin should be given, preferably by the intravenous route for open trauma 5.

Surgery should normally only be performed when the animal is stable (or as stable as possible). The most common indications for surgical intervention include the following 6 7 8 9: 

• All penetrating lesions to the thorax

• Progressive emphysema of the neck and thorax

• If there is internal organ damage or uncontrollable hemorrhage

• Progressive pneumothorax which cannot be controlled with thoracocentesis or thoracic drain 

• Pulmonary contusions that worsen despite treatment/mechanical ventilation 

• If there is communication between the pleural cavity and the peritoneal cavity

With respect to the last point, it can be said that diaphragmatic rupture usually results from abdominal, rather than thoracic, trauma; although they can undoubtedly cause significant secondary thoracic pathology, the treatment of diaphragmatic hernias is outwith the scope of this paper.

Traumatic pneumothorax

For all trauma patients, pneumothorax must be considered a possibility until proven otherwise 6. Bilateral thoracocentesis – usually best done with the animal in sternal recumbency – can be both diagnostic and therapeutic, and must be carried out before radiography (Figure 4). It is better to have a negative thoracocentesis than a dead animal on the X-ray table.

A closed pneumothorax generally does not require surgical intervention; such cases are often self-limiting and can be managed with thoracocentesis repeated as necessary – clinical evaluation of the patient should guide treatment 6 7. However, a drain tube should be considered if signs persist and the pneumothorax recurs despite repeated thoracocenteses (e.g., more than 2-3 times daily and/or for more than two days) or if excessive fluid (> 2 mL/kg/day) is present. 

When a pneumothorax requires surgical intervention, the surgical approach depends on the location of the lesion. If unilateral, a lateral thoracotomy offers the best approach. If bilateral, or the exact location of the lesion is unknown, a medial sternotomy is required 7. Note that pulmonary contusions (Figure 5) and mediastinal bleeding are also seen frequently after closed thoracic trauma, whether concomitant with pneumothorax or not. 

Traumatic hemothorax

Hemothorax is rare in animals (in contrast to the human situation) but significant blood loss into the pleural cavity can occur following trauma. Blood may be lost from damaged lung tissue or from laceration of the large pulmonary vessels, intercostal vessels or internal thoracic arteries. Thoracocentesis serves as both a diagnostic and therapeutic procedure, although ultrasound can also be useful to evaluate the amount of blood present, and repeat scans allow reassessment as required. If there is a considerable volume of blood, fluid therapy (crystalloids, colloids and blood) should be given 6.

Treatment of a traumatic hemothorax will depend on several factors, including the amount of blood present and the rate of blood loss into the pleural cavity, the type of trauma (open or closed), and the stability of the patient. Most cases secondary to closed trauma do not need surgery. A minor hemothorax with minimal respiratory distress should be treated conservatively, although the free blood should be removed if the animal develops labored breathing. When undertaking drainage of a hemothorax, it is not necessary to drain the thorax entirely, but sufficient blood should be removed to stabilize the patient; the drainage procedure should be done slowly whilst carefully monitoring the patient. Thoracocentesis may need to be repeated as necessary (Figure 6). If hemorrhage persists, or there has been severe blood loss into the pleural cavity, the patient may require a blood transfusion in addition to conventional fluid therapy. Autotransfusion is a quick and readily available method, but the blood must be collected aseptically and filtered blood bags should be used. If necessary consider placing an indwelling drain tube, and in extreme cases (e.g., if the bleeding does not resolve), exploratory thoracotomy may be necessary. However these cases have an increased risk of mortality. Remember that all penetrating thoracic lesions must be surgically explored, whether a hemothorax is present or not.

Thoracic trauma 

Closed trauma

For closed trauma cases, opinions vary as to which cases require exploratory surgery 5 6. Some clinicians recommend exploratory surgery for all cases where there are fractured ribs or flail chest, pulmonary contusions or pneumothorax, but the optimal time for surgery on these potentially unstable patients is unknown 12 13. The authors prefer to treat most closed trauma lesions conservatively and in general obtain good results.

An exception to this is thoracic trauma from bites. In some cases these may be considered to be “closed trauma”, as there may be minimal or no perforation of the skin; however, even if there is no visible break in the skin, all cases should be explored surgically, as a bite can frequently cause severe damage to the underlying tissues, including the intercostal muscles, ribs, intrathoracic blood vessels and internal organs (Figure 7). 

Penetrating wounds and open trauma

Any penetrating thoracic wound is a surgical emergency and the patient must be moved to the operating theatre as soon as possible. While the patient is being stabilized (oxygen, analgesics, fluids, etc.) the wound should be shaved, washed and covered so that the thorax is airtight and the pneumothorax resolved by thoracocentesis or drain tube 7 14. In general the degree of damage will be under-estimated on initial examination and even on radiography, especially when dealing with trauma secondary to bites 12 15; the full extent of the injury is often apparent only at surgery (Figure 8).

When dealing with bite wounds, all abnormal and damaged bone and soft tissue must be debrided and the entire area flushed copiously with sterile saline 7. Repair should be with absorbable, monofilament suture material and thoracic and subcutaneous drainage tubes should be placed as necessary 5 15.

In all cases wound closure must employ healthy, well-vascularized tissue, using muscle and omentum as necessary. Rarely, large wounds may require reconstruction using synthetic implants; note however that implants are contraindicated if the trauma has been caused by a bite, because of the risk of infection.

If the thoracic wall requires reconstruction, the options depend on the exact anatomical location. The diaphragmatic advancement technique may be useful, transposing healthy local tissue such as the external oblique abdominal muscle and/or latissimus dorsi muscle, and the omentum (Figure 9). If there is no damage to the pulmonary parenchyma, it is currently unclear if absolute rigidity of the thoracic wall is essential. Skin reconstruction, if necessary, may be achieved using a simple advancement flap, a rotation flap (utilizing the deep (subdermal) plexus) and/or an axial pattern flap (e.g., using the cranial superficial epigastric artery) 7. 

Good analgesia for these cases is paramount, and infiltration of the area with local anesthetic (or using a field block around the intercostal muscles) can allow better control of pain and thus improved ventilation.

At the end of the surgery, always verify if there is any leakage of air from the thorax by filling the area with sterile saline and gently inflating the lungs 5 15. A thoracotomy tube allows negative pleural pressure to be re-established as necessary and also allows aspiration of any intrapleural fluid, which should always be subjected to cytological evaluation. Any concurrent lesions (e.g., limb fractures) must be treated in a second surgical intervention once the animal is stable.

Rib fractures

Fractured ribs are intensely painful, which can result in hypoventilation. This may be exacerbated if a broken rib has caused lung damage 16 17 18. However, simple rib fractures from a closed trauma situation can generally be treated conservatively with pain control. Multiple rib fractures can lead to a flail chest developing; this may be suspected on physical examination if a paradoxical respiratory pattern is noted. For a flail chest to occur, at least two adjacent ribs must be fractured at two levels (ventrally and dorsally); the paradoxical respiratory movement results from the change in intrapleural pressure, such that the damaged section moves inwards during inspiration and outwards on expiration. The combination of abnormal airflow, underlying pulmonary trauma and pain predisposes to hypoxemia and hypoventilation. Stabilization of the fractured ribs is rarely performed but, along with pain relief, may improve ventilation in the polytraumatized patient. A return to full pulmonary function will require further treatment of the other associated pathologies. 

Note that pulmonary contusions can be progressive in nature, and in severe cases mechanical ventilation for 24-48 hours, along with supportive medical therapy, may be beneficial until a definitive repair can be effected. If there is extensive damage, a flail chest may be immobilized using percutaneous circumcostal sutures and an external splint, although this is rarely necessary. Otherwise fractured ribs can be stabilized by suturing them to the adjacent ribs; if the damage is severe, or secondary to a bite, it is usually preferable to resect them (Figure 10). In general, studies suggest that there is no difference in the prognosis whether or not a flail chest is stabilized surgically or treated medically 13, and the majority of flail chests caused by closed trauma do not require surgical intervention for stabilization and repair. However, it is worth re-emphasizing that surgical exploration is essential for all thoracic wall lesions caused by open trauma and for all thorax bites, even where the skin is not breached 8 9 10.

Post-surgical monitoring and treatment 

Following any surgery to the chest wall, respiratory and cardiovascular parameters must always be monitored post-operatively. This will include assessing the color of the mucosa and the capillary refill time, and measurement of arterial pressure and oxygen saturation. Hypothermia, hypotension and hypoventilation are the main potential complications. Oxygen therapy may be helpful since recovery may be slowed by pain, residual free air or fluid, dressings or secondary lung pathology. The intense pain from fractured ribs, along with any lung damage, contributes to hypoventilation 16 17 18 and hence pain management is vital in these patients. Optimal analgesia can be attained with systemic administration of suitable drugs (by bolus and continuous rate infusion as necessary) as well as transdermal patches, and/or local analgesia via intercostal and intrapleural infiltration using the thoracic tube. Blood gas analysis is often helpful, especially if there is hypoventilation. If necessary a drain tube may be placed to allow removal of any free air or fluid from the thorax. If there is free pleural fluid, it should be monitored carefully during the post-operative period; the fluid should be analyzed for bacterial growth and cellularity, and it is vital to determine the volume of fluid production and the trend (i.e., is it increasing or decreasing on a daily basis?) – ideally there should be less than 2 mL/kg/day, although reaching this figure is not mandatory.

Conclusion

Animals that have experienced thoracic trauma are often polytraumatized, and it is essential that the emergency veterinarian is able to accurately assess and prioritize such cases on presentation. Rapid diagnosis and appropriate treatment (e.g., immediate thoracocentesis) can make the difference between life and death for many of these patients and the clinician must be able to respond as necessary in these situations; it is important to remember that the initial thoracic pathology can sometimes worsen within the first 24-48 hours after trauma, and it is vital to ensure that the patient is carefully monitored and frequently reassessed during the post-trauma period.