How to Manage Penetrating Wounds in the Field

1. Introduction

Penetrating injuries to a body cavity such as the thorax or abdomen can result from a horse running into or attempting to jump over a fixed object in the field (fence post, tree, etc.). True penetrating wounds into the thoracic cavity and abdominal cavity are associated with a guarded prognosis due to pneumothorax and infection that develop.^1,2  Gunshot wounds penetrating only the skeletal muscle tend to have a good prognosis.³  Initial evaluation of a patient with a penetrating injury should focus on patient homeostasis.⁴

2. Penetrating Wounds to the Thoracic Cavity

Wounds must be carefully examined to ascertain the depth of penetration. A fence board may enter at the chest, sliding under the skin, creating a long penetrating wound down the side barrel of the horse. With no direct penetration to the chest (or abdomen), the basic principles of wound management should be used. A simple laceration may not appear to penetrate the thoracic cavity. However, the trauma associated with such a laceration may involve the ribs, which in turn can penetrate the pleural cavity, resulting in a pneumothorax.^1,4  A penetrating wound to the axilla can simply cause widespread subcutaneous edema from the “bellows action” of the wound but may also gain access to the thoracic cavity, resulting in a pneumothorax.²  A pneumothorax can be classified as either closed (lesion in lung parenchyma) or open (lesion in the thoracic wall). The horse will often exhibit increased respiratory effort, dyspnea, and flared nostrils. Additional findings may include subcutaneous emphysema, hemothorax, and pneumomediastinum.⁴  If a pneumothorax is suspected, the wound should be wrapped with a sterile airtight bandage^a  to minimize further influx of air into the thoracic cavity. Thorough auscultation must be performed. In the case of a pneumothorax, auscultation will reveal little to no air movement dorsally. Ultrasound (air echo that does not move with respiration) and radiographs (dorsal edge of the lung margin is apparent) can help confirm the diagnosis.^1,2,4,5 

The severity of the respiratory signs associated with pneumothorax depends on both the cause and the completeness of the horse’s mediastinum. Thoracocentesis should be performed to reestablish negative pressure.² This can be accomplished by placement of either a teat cannula or chest tube in the upper third of the chest (dorsally in the 13^th intercostal space along the cranial edge of the rib).^1,5 In either case, the site is clipped and aseptically prepared. A teat cannula or catheter can be attached to a 60-mL syringe via an extension set and three-way stop-cock. The air is removed by active suction.⁵

Once the horse is relatively stable, the wound should be explored in the standing patient. Local perineural intercostal anesthesia can help facilitate exploration. Routine wound debridement, lavage, and removal of foreign bodies should be performed. Once the wound has been thoroughly explored and cleaned, it should either be closed by primary intention or covered again with a sterile, airtight dressing and allowed to heal by second intention. The horse should be placed on broad-spectrum systemic antibiotics as well as nonsteroidal anti-inflammatories for pleural pain. Prognosis is good for survival if septic pleuritis does not develop and extrathoracic injury did not occur.⁵ Development of septic pleuritis decreases the prognosis for survival to 50%.⁶ A retrospective study found that horses tended to be euthanized when severe trauma to structures outside of the thoracic cavity was sustained (i.e., damage to the colon, etc.).⁶

3. Penetrating Wounds to the Abdominal Cavity

Wounds to the abdominal wall do not commonly penetrate the abdominal cavity. However, such lacerations can offer a diagnostic challenge due to the varying abdominal wall layers in different locations. The area around the wound should be clipped and prepared aseptically. Until peritoneal penetration has been ruled out, aseptic technique should be used.^2,4,5 Skin is much more resistant to tearing than are the fascia and the muscles underneath it.^2,4,5 Therefore, if the wound is small, it may be necessary to surgically open it so that the deeper layers can be thoroughly examined.

Diagnostics that can assist in determining whether the peritoneal cavity has been penetrated in less obvious injuries include abdominocentesis, ultrasound, and rectal palpation.⁵ If confirmation is not possible, the horse must be closely monitored for signs of peritonitis.⁵

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