Pain assessment in the dog: the Glasgow Pain Scale
Pain is an unpleasant personal emotional experience. It has 3 dimensions: Sensory – discriminative (location, intensity, quality, duration)...
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Issue number 25.3 Other Scientific
Published 21/04/2021
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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) and many patients will also have fractures (20-60% of cases).
Thoracic trauma cases are frequently seen in small animal clinics and should always be treated as an emergency.
Pneumothorax must be considered a possibility for all thoracic trauma patients until proven otherwise.
Bilateral thoracocentesis can be both diagnostic and therapeutic in pneumothorax cases, and must be carried out before radiography is attempted.
Hemothorax is rare in animals, but significant blood loss into the pleural cavity can occur following trauma.
Most cases of hemothorax secondary to closed trauma do not need surgery and can be treated conservatively.
Bites to the thorax can be very problematic; even if there is no skin perforation, some bites can cause massive internal damage. Surgical exploration of all bite wounds is mandatory.
The intense pain from fractured ribs, along with any lung damage, contributes to hypoventilation; good pain management is vital in these patients.
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:
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.
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:
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:
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.
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.
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.
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).
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.
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.
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