Page 85 - Problem-Based Feline Medicine

6 – THE CAT WITH HYDROTHORAX 77

Differential diagnosis ● Gram-positive rods – fluoroquinolones, chloram-
phenicol, clindamycin.
All causes of pleural effusion show similar signs of dys-
● Gram-positive cocci – beta-lactams, chloram-
pnea and dull chest sounds. Most other causes, however,
phenicol.
do not show the same severe systemic signs, other than
● Note: aminoglycosides require oxygen-rich envi-
some forms of pleural or pulmonary neoplasia.
ronments to be effective, and trimethoprim-sulfa
drugs may be inactivated in purulent debris. For
Treatment
these reasons, these medications are not indicated
Thoracostomy (T) tube placement and chest drainage in pyothoraces.
is the cornerstone of therapy.
Beta lactams such as ampicillin at 20–40 mg/kg IV ini-
● Tubes may be placed surgically or via a trocar.
tially q 4 hours for 48 hours, then PO q 6–8 hours are suf-
Placement along the ventral thoracic floor helps
ficient for the majority of community-acquired infections.
maximize complete drainage.
● Continuous underwater sealed suction with 20 Clindamycin is effective against Bacteriodes fragilis,
cmH O of vacuum appears to be superior to inter- found in approximately 15% of cases, and is dosed at
2
mittent drainage, but requires 24-hour direct super- 25 mg/cat PO q 12 hours.
vision. Disposable, self-contained collection units
Recommendation for length of antibiotic therapy varies
are easily adaptable to cats. These are commercially
from 4 to 12 weeks.
available one-piece plastic chambers that adapt to a
suction line on one end, and to the thoracostomy
tube on the other. The effusion is collected and vol- Prognosis
ume measured in the calibrated chamber.
Prompt, aggressive and complete drainage of the
● Occasionally bilateral T-tubes are required for
abscess cavity in the pleural space is essential for suc-
complete drainage. Average duration of tube use is
cessful therapy. The use of T-tube(s) with continuous
3–5 days with continuous suction. Intermittent suc-
suction has increased the treatment success rate of this
tion generally requires longer duration of therapy.
disease tremendously.
Tubes are usually removed once less than 2 ml/kg
of fluid is drained. Prognosis also varies with the presence or absence of
● Controversy exists as to the benefit of pleural underlying risk factors, such as pre-existing immuno-
lavage. There has been no convincing evidence suppressive disease with retroviral infection or sys-
showing any advantage to lavage, and the risk of temic neoplasia.
contamination is high.
With aggressive therapy, lack of significant risk factors,
Systemic support with IV fluid hydration and antibi- and long-term therapy with appropriate antibiotics,
otic therapy is very important. Most patients are hypo- prognosis is very good to excellent.
volemic on presentation, and the initial fluid losses via
the T-tube can be tremendous. Fluid requirements must Prevention
include volume replacement, maintenance, and on-
going losses through the T-tube. Keeping the patient Neuter intact males. Prevent roaming and fighting.
well-hydrated helps to promote the “dialysis mem-
brane” effect of the pleura, effectively “washing” the CHYLOTHORAX**
pleural space and draining the excess fluid through the
T-tube. Serum potassium and phosphorus levels should Classical signs
be monitred and supplemented, when indicated.
● Muffled heart and/or lung sounds ventrally.
● Exaggerated chest excursions with poor
Antibiotics
airflow.
Antibiotic selection is best based upon specific culture and
● Orthopnea (positional dyspnea with
sensitivity testing. Initial empirical choices can be based
reluctance to lie in lateral recumbency).
on the Gram stain of the cytology sample.