Elizabeth Rozanski, DVM, DACVIM, DACVECC
Traumatic thoracic injuries are prevalent in small animals, particularly in dogs. The most common causes of thoracic trauma are motor vehicular accidents and bite wounds. Other possible, although less common mechanisms include gunshot, knife wounds or being kicked by a larger animal (horse/cow). Injuries may range from mild to life threatening.
Tracheal stenting has been recently re-introduced as an approach to management of severe tracheal collapse. Severe tracheal collapse is life-threatening and while extra-thoracic collapse may be amenable to extra-luminal prosthetic rings, intra-thoracic collapse is not.
The purpose of this lecture is to review the management of pyothorax in cats and dogs. Pulmonary infection can result from bacterial, viral, fungal or protozoal infection, however, pyothorax is almost uniformly bacterial. The pleural space has a small amount of fluid normally (~ 5 ml) which serves as lubrication for the pulmonary parenchyma.
Pneumothorax is defined as free air in the pleural space. Normal intra-pleural pressure is about - 5 cmH20, which means that in order to equilibrate pressures, air from either the atmosphere, or the lung will equilibrate rapidly with the pleural space. Pneumothorax can be further characterized as traumatic, spontaneous and iatrogenic.
Respiratory distress is common and challenging. Cats often compensate well for pulmonary diseases, and some conditions can rapidly fulminate. Dogs are often more "honest" although they can decompensate rapidly as well. It is crucial to balance the equal goals of limiting stress on the patient with respiratory distress, and to work to identify the specific cause of the distress so that appropriate therapy can be provided.
Definitive diagnosis of pulmonary disease remains elusive at times. Cytological or histopathological samples are useful to help better classify the underlying cause as well as determine both prognosis and treatment course. Thus, it is prudent for the criticalist to have a strong grasp of the various techniques and options available for sampling.