Page 401 - Small Animal Internal Medicine, 6th Edition

CHAPTER 24 Disorders of the Pleural Cavity and Mediastinum 373

adequate drainage and should be assessed by radiography are seen on thoracic radiographs, the chest tube is removed
or ultrasonography. No obvious benefit is derived from the and the animal is monitored clinically for at least 24 hours
VetBooks.ir addition of antibiotics, antiseptics, or enzymes to the lavage for the development of pneumothorax or the recurrence of
effusion. Thoracic radiographs can be taken to more sensi-
solution. The addition of heparin (1000-1500 U/100 mL) to
the lavage fluid may decrease fibrin formation and has been
Thoracic radiographs are evaluated 1 week after removal
associated with better outcomes (Boothe et al., 2010). tively evaluate the animal for these potential problems.
All adapter ports connected to the chest tube should be of the chest tube and 1 week and 1 month after discontinu-
covered with sterile caps when not in use. When accessing ation of antibiotic therapy. These radiographs are obtained
the ports, the clinician should wear gloves and remember to so that a localized nidus of disease such as a foreign body or
wipe the ports with hydrogen peroxide before use. an abscess can be identified, and so that recurrence of a
Thoracic radiographs are taken every 24 to 48 hours to pyothorax can be detected before large volumes of pleural
ensure that the chest is being completely drained of fluid. fluid accumulate. Such niduses are often invisible when large
Failure to monitor the effectiveness of drainage radiographi- volumes of pleural fluid are present or when aggressive
cally can lead to costly prolongation of the intensive care therapy is in progress.
required for maintenance of the chest tube. Exploratory thoracotomy is indicated for the removal of
Serum electrolyte concentrations are also monitored. a suspected nidus of infection and in those animals that do
Many dogs and cats with pyothorax are dehydrated and ano- not respond to medical therapy. In the latter instance, surgery
rectic at presentation and require intravenous fluid therapy. may be necessary to remove fibrotic and diseased tissue or a
Supplementation of the intravenous fluid with potassium foreign body. Failure to respond is suggested by the contin-
may be necessary. ued need for a chest tube for longer than 1 week after the
The decision to discontinue drainage and remove the start of appropriate antibiotic treatment and drainage,
chest tube is based on fluid volume and cytologic character- although reported cases that have undergone complete
istics. The volume of fluid recovered should have decreased recovery after medical management have required drainage
to less than 2 mL/kg/day. Slides of the fluid are prepared by chest tubes for longer periods. Furthermore, persistence
daily and evaluated cytologically. Bacteria should no longer of large pockets of fluid in spite of appropriate chest tube
be visible intracellularly or extracellularly. Neutrophils will placement may necessitate the decision to perform a thora-
persist but should no longer appear degenerative (Fig. 24.3). cotomy earlier. Computed tomography of the chest may be
When these criteria have been met and no pockets of fluid a more sensitive method than thoracic radiography for

FIG 24.3
Cytologic preparation of a specimen of a pleural effusion from a cat being treated
successfully for pyothorax with chest tube drainage and antibiotics. Compared with the
fluid shown in Fig. 24.1, the nucleated cell count is low, the neutrophils are
nondegenerative, organisms are not present, and mononuclear cells are appearing
(cytocentrifuge prep).