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How to perform a pericardiocentesis
Removing pericardial effusion is important from both a diagnostic and a therapeutic standpoint.
Pericardial effusion is a frequent sequela to the common pericardial diseases of small animals. Removing pericardial effusion is important from both a diagnostic and a therapeutic standpoint. When cardiac tamponade is diagnosed, pericardiocentesis should be performed as soon as possible.
With supplies and equipment found in most veterinary hospitals, performing a pericardiocentesis is actually quite simple. Even in cases in which referral to a cardiologist or other specialist is your ultimate goal, you may need to perform a pericardiocentesis to stabilize a patient first. Although the technique is similar to that of thoracocentesis, the anatomical margins are narrower, and certain complications are more likely. That being said, adhering to the following protocol will maximize the likelihood of success.
Equipment and staffing
An electrocardiograph with an oscilloscope is recommended but not required. If one is not available, it is important that someone is available to monitor cardiac rhythm throughout the procedure by palpating pulses. We also recommend placing an intravenous catheter to administer fluids and emergency drugs if needed.
The following equipment and staffing are needed to perform a pericardiocentesis:
- Surgical scrub
- Intravenous catheters
—For large dogs: 14-ga, 5-in angiocatheters are optimal but 16-ga, 2½-in over-the-needle catheters will suffice
—For small dogs and cats: 16- to 18-ga, 2½-in over-the-needle catheters
- Scalpel blade
- Extension set
- Three-way stopcock
- 60-, 12-, and 3-ml syringes
- 25-ga ¾-in needle
- 2% lidocaine
- Sterile gloves
- Plain (red-top) or serum separator tube
- EDTA and red-top tubes for cytology samples (and for bacterial culture and antimicrobial sensitivity testing, if indicated)
- Felt-tip marker
- Assistants (preferably two; nonsterile)
Here we describe the technique for pericardiocentesis in dogs, but the same protocol is followed in cats by using smaller catheters.
You can perform this procedure from the right or left side of the thorax. It is easiest to perform with the patient in lateral recumbency to minimize motion. As mentioned earlier, if available, attach an electrocardiograph with an oscilloscope to the patient. If electrocardiography is not available, have an assistant monitor the cardiac rhythm by palpating the patient's pulse throughout the procedure. One assistant restrains the patient, and another helps you perform the procedure.
Pericardiocentesis can be performed using a right or left thorax approach because when marked pericardial effusion is present, pericardial distention pushes the lungs dorsally, resulting in a "cardiac notch" on the right and left side. The decision is based on your experience or if fluid accumulation is asymmetric (which rarely occurs). We prefer the left-sided approach for the following reasons:
1. It is easier to recognize iatrogenic puncture of the left ventricle than of the right ventricle. The oxygenated blood in the left ventricle is bright red. Both right ventricular blood and pleural effusion are dark red.
2. The high left ventricular pressure usually results in a pulsatile, high-velocity flashback into the catheter, making it obvious if you have penetrated the left ventricle.
3. The right ventricular wall is much thinner than the left ventricular wall, so it is easier to penetrate it unknowingly as you advance the needle and catheter.
Some practitioners, nonetheless, prefer approaching the pericardial sac from the right. Although we describe a left-sided approach here and in the photographs, a right-sided approach can be performed using the same landmarks. Many people prefer performing pericardiocentesis from the right side since there is a "cardiac notch" between the right cranial and caudal lung lobes where the risk of lung puncture is diminished. Furthermore, it is thought that there are fewer coronary vessels on the right side of the heart as it sits in the thoracic cavity. As there are major coronary and thoracic vessels on both sides of the thoracic cavity, whether a right-sided approach translates to a significant reduction in risk of side effects has not, to our knowledge, been documented.
To begin, palpate the thoracic wall for the point of maximal intensity (PMI), and clip a large area of fur centered on that spot. Select a location for catheter introduction in the intercostal space nearest the apex beat (typically the seventh or eighth intercostal space). Perform an initial scrub before injecting the lidocaine. Use a 3-ml syringe with a 25-ga, ¾-in needle to infiltrate 1 to 2 ml of lidocaine to create a local block cranial to the rib. We recommend blocking the area where the pericardiocentesis needle will enter, which is cranial to the rib, to avoid damaging the neurovascular bundle caudal to the rib. Be sure to infiltrate the skin, intercostal muscle, and pleural lining to completely desensitize the region and ensure patient comfort throughout the procedure. Administer a bleb of lidocaine subcutaneously, and slowly insert the needle until you meet resistance from the pleural lining. Then inject lidocaine as you slowly withdraw the needle along the tract.
Once the needle is withdrawn, perform a full surgical prep of the area, using the subcutaneous lidocaine bleb as the center. Some clinicians use a skin-marking pen to mark the injection site to ensure accurate catheter placement should the lidocaine bleb not persist. When this technique is used, sedation is rarely needed unless the patient is particularly fractious.
A 14-ga, 5-in catheter is ideal for most medium- to large-breed dogs, but you can use a 16-ga, 2½-in catheter in smaller dogs or if a larger catheter is not available. Glove and use a scalpel blade to carefully add holes in the catheter's sides near its tip (Figure 1). This will maximize flow if the catheter tip becomes occluded. Be sure you don't produce any burrs.
1. Carefully making two or three notches in the catheter sides with a scalpel blade can greatly increase fluid flow and reduce the likelihood of obstruction. Be sure you do not produce any burrs in the process.
Slowly introduce the catheter through the skin and thoracic wall at the blocked site (Figure 2) until you feel a pop, which usually corresponds to the catheter's entering the pleural space.
2. The site for catheter entry is at the palpable apex beat. Direct the catheter toward the opposite scapula.
Slowly advance the catheter and needle toward the opposite scapula and into the pericardial sac while monitoring the heart rhythm (by using an electrocardiograph or by monitoring pulses). Once the catheter is in the pericardial space, a flash of pericardial fluid will be obtained (most often port wine in color). Advance the stylet and catheter slightly farther, and, while holding the stylet in place, advance the catheter over the stylet until the catheter is well inside the pericardial sac. Remove the stylet.
Since most pericardial effusions look like port wine or frank blood, you need to be sure that the fluid you are withdrawing is the effusion and not blood from iatrogenic puncture of a vessel or cardiac chamber. To make sure, remove a sample with the 12-ml syringe, and place it in a serum separator or a plain (red-top) tube, and monitor it for clotting. If it does not clot after one or two minutes, you can usually assume the fluid is effusion, not blood, and you can proceed with rapid pericardial effusion withdrawal with a larger, 60-ml syringe. However, remember that blood from an active hemorrhage (as in the case of a left atrial tear or an actively bleeding tumor) also will not clot.
As soon as you have removed the needle from the catheter, attach one end of the extension set to the catheter hub and the other end to the stopcock and a 60-ml syringe. Apply suction and evacuate the fluid as quickly as possible (Figure 3).
3. The catheter is stabilized against the patient while pericardial fluid is aspirated.
To maximize flow, sometimes you will need to move the catheter slightly, rotating, tilting, or slowly withdrawing and advancing it. Remove as much pericardial fluid as feasible, but it may not be possible to remove it all. Usually small residual volumes will drain from the pericardial puncture site and be reabsorbed across the pleural membrane.
Once you can no longer pull fluid into the syringe, remove the catheter with the extension set still attached. Occasionally, rubbing of the catheter on the cardiac surface will stimulate arrhythmias, and, if severe, you should immediately remove the catheter. A skin bandage is not necessary, and dogs can often be discharged the day of the procedure. Place samples of the effusion in EDTA and plain tubes for analysis, and record the total fluid volume withdrawn. Antibiotic treatment is unnecessary as long as sterile technique is maintained.
Ultrasound guidance can be helpful if the effusion volume is small, but it is difficult to maintain sterility in the field while manipulating an ultrasound probe. Therefore, we do not recommend using ultrasonography during the pericardiocentesis procedure itself. It can be used, however, to select a site for catheter placement and to assess residual pericardial effusion.
Upon successfully draining the pericardial effusion, the patient's cardiovascular parameters should improve immediately. Once intrapericardial pressure falls, right heart filling improves, cardiac output increases, oxygenation improves, pulse strength improves, and heart rate drops.
The most common complication of pericardiocentesis is cardiac arrhythmia due to epicardial irritation or cardiac puncture. Withdrawal of the catheter usually stops the arrhythmias. If the heart or vena cava is punctured, it is possible to remove a large amount of blood. Therefore, it is crucial to monitor the presumed effusion for clotting.
There is also a small risk of lung or coronary artery laceration. Although very rare, lung laceration may result in pneumothorax, and coronary laceration may result in an infarct or even sudden death. Fortunately, following good technique makes these consequences rare.
Ideally, all of the pericardial effusion will be removed, but marked clinical benefit is derived from even modest decreases in intrapericardial pressure. Once a catheter has entered the pericardial sac, it is difficult to avoid cardiac puncture if you immediately attempt a second pericardiocentesis (i.e. if the catheter was inadvertently withdrawn from the pericardial sac). Therefore, you should only repeat the procedure if cardiac tamponade is present or persists.
If the pericardial sac has been punctured but the catheter has been withdrawn before the fluid is removed, it is presumed that the effusion may drain to the thorax. Depending on the animal's clinical signs, the fluid is left to be reabsorbed.