Page 211 - Small Animal Internal Medicine, 6th Edition

CHAPTER 9 Pericardial Disease and Cardiac Tumors 183

evaluated for a coagulation disorder. When trauma-induced larger catheter), sterile ethylenediaminetetraacetic acid
intrapericardial hemorrhage persists in an animal with (EDTA) and clot (red-top) tubes for fluid samples, and a
VetBooks.ir normal hemostasis, surgical exploration is indicated. large fluid collection receptacle. Personnel able to help
restrain the animal and assist with fluid aspiration also are
PERICARDIOCENTESIS
The skin is shaved and surgically prepared over the right
Pericardiocentesis should be done right away in animals with essential.
cardiac tamponade. As noted earlier, diuretic or vasodilator precordium, from about the third to seventh intercostal
use is not indicated and can exacerbate hypotension and spaces and from sternum to well above the costochondral
cause cardiogenic shock. When possible, a peripheral IV junction. Before the final scrub, locate and mark the point
catheter should be placed before pericardiocentesis. This of strongest precordial impulse; this usually is between
allows for IV fluid administration to support cardiac output the fourth and sixth rib near the costochondral junction.
during preparations for the pericardial tap procedure, and Usually this is the best site for needle entry. Ultrasound also
provides access for sedative, antiarrhythmic, or other drug can be used to locate an optimal puncture site. Infiltrate
administration as needed. Continuous ECG monitoring a small volume of 2% lidocaine (0.5-1 mL) into the skin
during the procedure is important because needle or cath- and underlying intercostal muscle to the pleura at the punc-
eter contact with the heart commonly causes ventricular ture site (alternatively, some clinicians prefer to do this later
arrhythmias. using sterile technique). Local anesthesia is necessary when
Pericardiocentesis is a relatively safe procedure when per- using a larger catheter and also recommended for needle
formed carefully. Removal of even a small volume of peri- pericardiocentesis.
cardial fluid can markedly decrease intrapericardial pressure After sterile skin preparation is complete, don sterile
in animals with tamponade. Pericardiocentesis is usually gloves and prepare the drainage catheter assembly. When
approached from the right chest wall to minimize the risk of using a large-gauge catheter, a couple of tiny (~1 mm) side
trauma to the lung (via the cardiac notch) and major coro- holes can be cut (smoothly) with a sterile sharp blade or iris
nary vessels (located mostly on the left). The need for seda- scissors near the catheter tip to facilitate fluid drainage. Care
tion depends on the clinical status and temperament of the must be taken to offset these holes from each other and avoid
patient. The animal usually is placed in left lateral or sternal making them too large, so that the catheter tip is not exces-
recumbency for more secure restraint, especially if the sively weakened, lest it break off within the pericardium or
animal is weak or excitable. Although, in some cases, needle pleural space. Carefully replace the catheter over the needle/
pericardiocentesis can be performed successfully on the stylet and attach the extension tubing to this. Then attach the
standing animal, the risk of injury increases with sudden three-way stopcock to the other end of the tubing, and the
movement. An alternative approach is to use an elevated collection syringe to the stopcock. The stopcock should be
echocardiography table with a large cutout, if available; the set “off” to air. If not done previously, infiltrate lidocaine
animal is placed in right lateral recumbency, and the tap is (with sterile technique) at the puncture site. When using a
performed from underneath. An advantage to this method large-gauge catheter system, make a small stab incision into
is that fluid moves to the right (dependent) side with gravity; the skin to facilitate catheter entry. The puncture should be
however, if adequate space is not available for wide sterile just cranial to the closest rib; when entering the chest, care
skin preparation or needle/catheter manipulation, this should be taken to avoid the intercostal vessels that run
approach is not advised. Echocardiographic guidance can be caudal to each rib.
used but generally is not necessary unless the effusion is of Before inserting the needle/catheter into the chest, pass
small volume or appears compartmentalized. the attached collection syringe to an assistant. Although a
A variety of equipment can be used for pericardiocentesis. perpendicular orientation of needle/catheter to the skin ini-
A butterfly needle/catheter (19- to 21-gauge) or appropri- tially may help avoid intercostal vessels, it often is helpful to
ately long hypodermic or spinal needle attached to extension “aim” the needle tip toward the point of the patient’s opposite
tubing is adequate in emergency situations. However, an (left) shoulder as the chest is entered. Once the needle has
over-the-needle catheter system can be a safer alternative penetrated the skin, the assistant should gently apply nega-
because it reduces the risk of cardiopulmonary laceration tive pressure to the attached syringe as the operator slowly
during fluid aspiration. The catheter is chosen according to advances the needle toward the heart. This way, any fluid will
patient size. For example, a 12 to 16 gauge, 10 to 15 cm (4- to be detected as soon as it is encountered. Pleural fluid, usually
6-in) long catheter system, or a commercially available over- straw-colored, may enter the tubing first. It is important to
the-wire pericardial drainage catheter allows for faster fluid hold the needle/catheter steady during insertion to avoid
removal in large dogs. For small dogs, an 18 to 20 gauge, 3.75 extraneous motion of the sharp tip within the chest. When
to 5.0 cm (1.5-2.0 in) long catheter could be adequate. Addi- contacted, the pericardium creates increased resistance to
tional equipment to assemble before the procedure includes needle advancement and may produce a subtle scratching
sterile extension tubing (except if using a butterfly needle), sensation. With gentle pressure, slowly advance the needle
a three-way stopcock, a 20 to 60 mL collection syringe, a through the pericardium. A loss of resistance may be felt
3-mL syringe and small-gauge needle for local block, lido- with needle penetration, and pericardial fluid (usually dark
caine, small surgical blade (for stab incision when using a red) will appear in the tubing. During initial insertion, the