Page 31 - Feline Cardiology

22 Section A: Clinical Entities

Clinical Entities

A B C

Figure 3.3. Echocardiograms from a normal cat (A), a cat with pericardial effusion (B), and a cat with pericardial effusion and pleural
effusion (C). The yellow arrows indicate pericardial effusion; the red arrows indicate pleural effusion.

performed once the cat’s respiratory effort and rate have
improved following thoracocentesis. If atrial enlarge- Box 3.2. Thoracocentesis procedure
ment is not evident, a cardiogenic cause of the pleural For most cats, a 19 gauge butterfly catheter is the easiest meth-
effusion is very unlikely. Pleural effusion is visible on od for thoracocentesis, and the animal is usually restrained in
thoracic ultrasound as intrathoracic anechoic space sur- sternal recumbency. In very obese cats, an 18 gauge over-the-
rounding the heart and lungs. If the effusion is cellular needle catheter may be necessary to penetrate the body wall
or contains a marked amount of fibrin, echogenic debris (kinks easily; body wall stability is important to reduce this
may be visible floating in the free fluid. Pericardial effu- occurrence). Most animals tolerate the procedure well, but
sion is also usually anechoic in appearance (Figure 3.3). adequate sedation is important when required. When using
Therapeutic thoracocentesis should be performed in sedation, it is best to choose medications that will not depress
any cat that is dyspneic in association with moderate or cardiac or respiratory function. Mild sedation can be achieved
marked pleural fluid accumulation. Diuretic therapy is with 0.3 mg/kg butorphanol and 0.3 mg/kg midazolam IV or
useful to slow future pleural effusion development, but IM, if necessary. Local anesthesia (1 cc of 2% lidocaine) may
it is not adequate therapy alone in a dyspneic animal. be helpful and allow the clinician to avoid sedation in some
See Box 3.2 for a description of the centesis technique. animals. A 3-way stopcock should be placed between the
butterfly and a 35–60 cc syringe (Figure 3.4). The stopcock
Thoracocentesis is useful for therapeutic and diagnostic minimizes the risk of pneumothorax as the syringe is used
purposes. Although there may be considerable overlap to withdraw effusion with gentle pressure. If available, ultra-
between fluid type and underlying disease, cytologic sound guidance is optimal to ensure the butterfly is directed
evaluation can be helpful to directly identify the under- toward an effusion pocket. If ultrasound is not available to
lying cause of fluid accumulation, particularly in cases localize the largest pocket of fluid accumulation, the centesis
of neoplasia. Cardiogenic effusions are usually sterile is performed at the 7th or 8th intercostal space at the costo-
and therefore bacterial cultures are not routinely per- chondral junction. The thorax is widely clipped and surgically
formed if the effusion appears to be cardiac in origin. prepped. Some clinicians wear sterile gloves and others do
In cats with congestive heart failure and pleural effu- not; in either case, the sterile field must remain intact during
sion, respiratory rate and effort should be monitored the procedure and reprepped if sterility is broken. The needle
closely by the owner after discharge from the hospital to is advanced through the skin, subcutis, and intercostal mus-
determine when repeat ultrasound examinations or cles and pleura while one or two technicians gently restrain
and distract the patient. Negative pressure is applied continu-
radiographs are warranted, when medication changes ously until fluid appears within the syringe (Figure 3.5). The
are necessary, and/or when repeat thoracocentesis is effusion is withdrawn until resistance to the suction is felt. The
necessary. The authors find it helpful for owners to gold standard for preventing thoracocentesis-associated com-
maintain a log of the daily respiratory rates in animals plications, measurement of intrapleural pressures, is not yet
with congestive heart failure. Owners are directed to used clinically in feline medicine. Limitations to the number of
contact us if the respiratory rate begins to rise. Typically, times the procedure can be performed consist of the cat’s tol-
a cat that is comfortable and free of large-volume pleural erance, compliance of the lungs, the owner’s ability to return
effusion should have a respiratory rate at rest that is less for treatments, and rarely protein loss (exudates).
than 30 breaths/minute in the home environment. This
method allows worsening heart failure to be addressed