Page 400 - Small Animal Internal Medicine, 6th Edition

372 PART II Respiratory System Disorders

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FIG 24.1
Cytologic preparation of a specimen of a pleural effusion
from a cat with pyothorax. Degenerative neutrophils
predominate, and intracellular and extracellular bacteria are FIG 24.2
prevalent (arrowheads). Both rods and cocci are seen. Pleural fibrosis manifested by markedly thickened pleura
seen during thoracotomy in a cat with chronic pyothorax.
Treatment with antibiotics alone was attempted, and several
weeks later the cat’s condition deteriorated. Fibrosis was
Oral antibiotics are used once significant improvement is too extensive to allow for routine drainage with chest tubes.
noted, usually about the time of chest tube removal. Surgical debridement, several lobectomies, drainage
Amoxicillin-clavulanate (dogs, 11 mg/kg q8h; cats, 12.5 mg/ through surgically placed tubes, and long-term antibiotic
kg q8h) is used in patients that have responded with ampicil- therapy resulted in a cure.
lin with sulbactam. Oral antibiotic therapy is continued for
an additional 4 to 6 weeks.
Drainage of the septic exudate is an essential part of the allow monitoring of collected fluid volume and adjustment
treatment of pyothorax. Although treatment with antibiotics of suction pressure. An initial suction pressure of 10 to
alone often causes dramatic improvement in the animal’s 15 cm H 2 O is used, but more or less pressure may be neces-
clinical condition initially, the signs generally recur, and sary depending on the viscosity of the pleural fluid and the
complications of prolonged infection, such as fibrosis and collapsibility of the tubes. The collection systems must be
abscessation requiring surgical debridement and drainage, carefully monitored for leaks or malfunctions that could
are more likely (Fig. 24.2). Indwelling chest tubes provide the cause a fatal pneumothorax.
best drainage and can be used to keep the exudate from Intermittent suction by syringe is ideally performed every
accumulating during the initial days of antibiotic therapy. 2 hours for the first days of treatment, with arrangements
Dogs and cats in critical condition at presentation are stabi- made for drainage to continue during the night. Within a
lized through the use of needle thoracocentesis and shock few days the volume of fluid produced will decrease, and the
therapy before chest tube placement. Intermittent needle interval can then be lengthened. If such intensive care is not
thoracocentesis is a poor substitute for chest tube draining possible, an effort should still be made to empty the chest of
in this setting and is rarely sufficient to achieve resolution of fluid at least once late in the evening to minimize the accu-
infection. Intermittent thoracocentesis is not recommended mulation of exudate overnight.
unless the owner cannot afford the expense of chest tube Lavage of the chest cavity is performed twice daily and
management and the remaining option is euthanasia. consists of the removal of any fluid within the chest, followed
Chest tube placement and assessment of positioning are by slow infusion of warmed sterile saline solution into the
discussed in Chapter 23. Animals probably respond most chest. A volume of approximately 10 mL/kg of body weight
rapidly to constant suctioning of exudate from the chest, is infused, but the infusion should be discontinued if any dis-
although intermittent suction is certainly adequate and often tress is noted. After this the animal is gently rolled from side
more feasible. Constant suction is applied with a suction to side, and the fluid is removed. Sterile technique is used
pump and collection unit. Disposable pediatric cage-side throughout the procedure. The volume recovered should be
collection units (e.g., Argyle Thora-Seal III, Medtronic) are about 75% of the volume infused. If less fluid is retrieved,
available through hospital supply companies. These units this may indicate that the chest tube is no longer providing