Trauma

Rib fractures are often significant from the standpoint of pain management. The patient may hypoventilate if severe discomfort is present during respiration. Although rib fractures do not routinely require stabilization, their presence should alert the clinician to the possibility of underlying soft tissue thoracic injury, including pulmonary contusions, diaphragmatic hernia, hemothorax, and/or pneumothorax. If the rib fractures are very unstable, they can cause further trauma to the surrounding tissues and intrathoracic structures (i.e., lungs), thus necessitating surgical intervention.²

Flail Chest and Intercostal Muscle Damage

Flail chest is defined as a “fracture of several adjoining ribs resulting in a segment of thoracic wall that has lost continuity with the rest of the hemithorax.”² This results in the fractured segment moving paradoxically throughout respiration. During inspiration, as the chest wall moves outward, the flail segment collapses inward due to negative intrapleural pressure and vice versa.²

Respiratory distress often occurs in patients with flail chest. There are two are reasons for this. First, patients can hypoventilate purely because of pain. Second, many animals with flail chest have other lung injuries, such as pneumothorax, hemothorax, pulmonary contusions, or a diaphragmatic hernia, which can increase the degree of hypoxemia.

Management of flail chest can be purely medical or a combination of medical and surgical. Initially, the patient should be laid down on the side with the flail segment, or the chest can be wrapped. This reduces bulging of the segment during exhalation (although it will still be pulled inward with inhalation) to minimize pain and secondary trauma. If ventilation is severely impaired, intubation and manual ventilation may be lifesaving in that it may ensure that a tension pneumothorax is not present before positive-pressure ventilation is initiated (see Chapter 213, Basic Mechanical Ventilation). Aggressive analgesia is often helpful, although the animal should be monitored closely for respiratory depression and mechanical ventilation provided if necessary (see Chapters 164 and 213, Analgesia and Constant Rate Infusions and Basic Mechanical Ventilation, respectively).

Time and cage rest are often the treatment of choice. An external stabilization splint, which covers the affected and unaffected surrounding areas and is sutured to the chest wall, has been used to provide chest wall support. Whether or not to surgically stabilize the flail chest segment is controversial. Often the actual flail segment contributes very little to dyspnea, hypoxemia, or hypoventilation, and pain or coexisting disease is the primary cause of these abnormalities. However, surgically stabilizing the segment reduces pain and improves thoracic wall excursion and ventilation, and should be performed if anesthesia and surgery are required for other reasons. If the flail segment is displaced or adding to further lung dysfunction (laceration of the lung or vasculature by the flail segment), surgery is necessary (see Chapter 153, Thoracic Trauma).

Tearing of the intercostal muscles secondary to fractured ribs or a penetrating injury may cause a loss of chest wall rigidity and paradoxical movement of the affected area or flail segment. The degree of ventilatory impairment depends on the size of the destabilized area. This condition rarely causes direct respiratory impairment, but rather leads to pain and may be a sign of additional injuries.