Page 212 - Small Animal Internal Medicine, 6th Edition

184 PART I Cardiovascular System Disorders

extension tubing is attached to the needle stylet. The needle/ the catheter tip has penetrated a cardiac chamber, the bubbles
catheter unit must be advanced far enough into the pericar- will appear within the heart.
VetBooks.ir dial space so that the catheter is not deflected out of the Complications of Pericardiocentesis
pericardium as the needle stylet is removed; advance the
catheter before pulling back on the stylet. After advancing
arrhythmias (the most common complication, although
the catheter into the pericardial space and removing the Complications can include cardiac injury or puncture causing
needle, attach the extension tubing directly to the catheter. usually self-limiting when the needle is withdrawn); lung
Initial pericardial fluid samples should be saved into the laceration causing pneumothorax and/or hemorrhage; coro-
sterile EDTA and serum clot tubes for evaluation. Then aspi- nary artery laceration with myocardial infarction or further
rate as much pericardial fluid as possible. When fluid drain- bleeding into the pericardial space; dissemination of infec-
age becomes difficult or stops, adjusting the catheter position tion or neoplastic cells into the pleural space; and, occasion-
slightly or tilting the patient more sternally may allow addi- ally, death.
tional fluid retrieval. A small backflush into the catheter also
may help.
If the needle contacts the heart, a prominent scratching CONSTRICTIVE PERICARDIAL DISEASE
or tapping sensation usually is felt, the needle may move with
the heartbeat, and ventricular premature complexes are often Etiology and Pathophysiology
provoked. The needle should be retracted slightly if cardiac Constrictive pericardial disease is diagnosed occasionally in
contact occurs. It is important to avoid excessive needle dogs but only rarely in cats. This condition occurs when
motion within the chest. thickening and scarring of the visceral, parietal, or both peri-
When no additional pericardial fluid can be aspirated, the cardial layers restrict ventricular diastolic expansion and
catheter is slowly withdrawn under continued but gentle prevent normal cardiac filling. Both ventricles are affected.
negative pressure. A quick echocardiographic recheck should Usually the entire pericardium is involved symmetrically.
verify whether tamponade is resolved, cardiac filling is Fusion of parietal and visceral pericardial layers obliterates
improved, and if any pericardial fluid remains. If substantial the pericardial space in some cases. In others, the visceral
pericardial effusion remains, pericardiocentesis is repeated layer (epicardium) alone is involved. A small amount of peri-
using a fresh catheter system and slight adjustment in the cardial effusion (constrictive-effusive pericarditis) may be
patient’s position, if needed. A sample of the effusion should present.
be submitted for fluid analysis and cytologic evaluation, and Although the etiology of constrictive pericardial disease
additional fluid reserved in the sterile clot tube for possible often is unknown, acute inflammation with fibrin deposition
culture, pending cytology results. Further echocardiographic and possibly varying degrees of pericardial effusion are
monitoring of the patient for acute recurrence of pericardial thought to precede its development. Some cases in dogs were
effusion before hospital discharge is wise, especially with attributed to recurrent idiopathic hemorrhagic effusion,
suspected HSA. infectious pericarditis (especially from coccidioidomycosis
but potentially also from actinomycosis, mycobacteriosis,
Verifying Catheter Location blastomycosis, or bacteria), a metallic foreign body in the
Pericardial effusion usually appears quite hemorrhagic. It pericardium, tumors, prior PPDH surgery, and idiopathic
can be distressing to see dark, bloody fluid being aspirated pericardial osseous metaplasia and fibrosis.
from near the heart, but pericardial fluid can be differenti- Increased fibrous connective tissue and variable amounts
ated from intracardiac blood in several ways. Unless the fluid of inflammatory and reactive pericardial infiltrates are seen
is caused by recent pericardial hemorrhage, it will not clot. on histopathologic examination. Pericardial fibrosis creates
A few drops can be placed on the table or into a serum tube a stiff shell around the heart and increases ventricular inter-
to check this. The PCV of pericardial fluid usually is much dependence. Ventricular filling is limited to early diastole,
lower than that of peripheral blood (except in some dogs after which ventricular expansion is abruptly curtailed, in
with HSA); also, the supernatant is xanthochromic (yellow cases of advanced constrictive pericardial disease. Any
tinged). As the pericardial fluid is drained, the animal’s ECG further ventricular filling is accomplished only at high
complexes usually increase in amplitude, tachycardia dimin- venous pressures. Compromised filling reduces cardiac
ishes, and some dogs take a deep breath and appear to be output. Compensatory neurohormonal activation causes
more comfortable. On the other hand, if intracardiac blood fluid retention with congestive signs of pleural effusion and
is being aspirated, the patient is likely to become more tachy- ascites, as well as tachycardia and vasoconstriction.
cardic and hypotensive. Another method to verify catheter
location, if an echo/ultrasound transducer is available, is to Clinical Features
rapidly inject a small bolus of sterile, agitated saline through Middle-aged, large- to medium-breed dogs are affected most
the pericardiocentesis catheter (via the three-way stopcock) often. Males and German Shepherd Dogs may be at higher
to create an echocontrast (“bubble”) study. If the catheter tip risk. Some dogs have a history of pericardial effusion. Clini-
is within the pericardial space, small bright microbubbles cal signs of right-sided CHF predominate. Abdominal dis-
will appear within the pericardial fluid around the heart. If tention (ascites), tachypnea or labored breathing, tiring,