If you know how to place an IV catheter in a dog or a cat, you can perform pericardiocentesis. I actually think it’s much easier than feeding an IV catheter into a tiny little cat vein. It might be scary your first or second time, but you got this. Pericardiocentesis can be lifesaving, and in many cases, you will see an immediate and dramatic improvement that is so rewarding. So roll up your sleeves, take a deep breath and relax. Your patient needs you, and you can do this.
Everyone’s technique might differ slightly, but I’m going to walk you through the way I do it, because I think it’s easy and fun.
In this video, we will demonstrate how to do pericardiocentesis in a dog.
Diagnosing Cardiac Tamponade and Indications for Pericardiocentesis:
Pericardial effusion resulting in cardiac tamponade is relatively common in dogs, while rare in cats.
There are many causes of pericardial effusion, including cancer, infections, foreign material within heart failure, scar tissue around the heart, tearing of the atrium (this can be a complication of atrial enlargement resulting from valvular insufficiency), trauma to the heart, problems of the blood clotting system, and congenital abnormalities (i.e. Peritoneopericardial diaphragmatic hernia. In idiopathic pericardial effusion, the fluid accumulates spontaneously without any identifiable cause.
In dogs, pericardial effusion is most often a manifestation of hemangiosarcoma, followed byidiopathic pericardial effusion, mesothelioma, and heart base tumors. In cats, pericardial effusion most often results from heart failure, lymphosarcoma and FIP.
The symptoms of pericardial effusion can vary greatly depending upon the severity of the effusion, and whether the effusion is acute or chronic. The clinical signs can also be very subtle, and so the diagnosis can be easily missed.
Cardiac tamponade means that the degree of fluid accumulation is significant enough that it’s affecting the patient’s cardiovascular parameters and circulation. Tamponade results when the increased pressure within the pericardial space equals or exceeds the ventricular filling pressures, compressing the heart, preventing the chambers from filling. The pericardium does not stretch very easily, so a large volume of pericardial effusion usually suggests that the effusion has accumulated gradually, allowing the pericardium to stretch with time. A large volume of ascites can also suggest chronic/gradual accumulation of pericardial effusion.
Owners may report loss of energy, poor appetite, vomiting, diarrhea, weight loss, exercise intolerance, labored breathing, abdominal distention, weakness, even seizures.
On physical examination, you may notice muffled or absent heart sounds (most of the time but not always), weak or variable pulses, pale mucous membranes, tachycardia, ascites and distended jugular veins.
For me, ultrasound is by far the easiest way to diagnose pericardial effusion. It’s quick, easy, minimally invasive, and is a very sensitive diagnostic test. A focused ultrasound of the pericardial space (as well as the thoracic and abdominal cavities) to check for any significant cavitary effusion can usually be performed in less than 5 minutes, without shaving any fur (use alcohol), and with the patient resting comfortably in sternal recumbency (click here to learn how to perform a focused ultrasound for cavitary effusion).
You don’t need a fancy $30,000 ultrasound machine for most emergency procedures. I think our unit is from 1989 and it does the job. We got it for less than $3000 used from a radiology technician. These units are priceless for helping to identify fluid in the body cavities and ultrasound-guided centesis.
The diagnosis of pericardial effusion is much more challenging without ultrasound. This might surprise you, but thoracic radiographs are NOT considered reliable for the diagnosis of pericardial effusion resulting in cardiac tamponade. 1 The radiographic findings that typically come to mind (enlargement of the cardiac silhouette, globoid appearance of the cardiac silhouette, and convexity of the dorsocaudal aspect of the cardiac silhouette) are not very sensitive or specific for cardiac tamponade attributable to pericardial effusion. In very acute cases, significant enlargement of the cardiac silhouette might not be apparent at all on x-ray. In the highly compromised patient, the degree of stress, restraint or sedation that is typically required for x-ray may result in sudden decompensation.
Without ultrasound, a presumptive diagnosis could only be made with extreme caution, and only in situations where the constellation of clinical findings is highly supportive.
Other findings to note may include electrical alternans on EKG (characterized by change in the amplitude of the QRS complex and sometimes a wandering baseline, as the heart swings back and forth in the pericardial sac), pulsus paradoxicus (a drop in blood pressure and pulse strength/quality during inspiration), and concurrent abdominal or pleural effusion.
Pericardiocentesis is indicated for the emergency treatment of overt cardiac tamponade. It may not be appropriate or worth the risk in patients that are asymptomatic and cardiovascularly stable.
The procedure is not without risk, and everyone, including the owner, should be made aware that some patients can decompensate during the procedure, and complications such as cardiac arrhythmia, ongoing hemorrhage, and death can occur during the procedure or afterwards.
Before you start:
Prepare the Patient:
First, you need to prepare your patient. Remember, many of these patients are very sick, often dying. SO they need to have: supplemental oxygen, an IV catheter in place (remember, this is your lifeline), and monitoring equipment should be applied (minimally EKG, but also blood pressure and SPO2 are helpful).
I like to make sure that my patients are comfortable, relaxed, and free from anxiety and pain at all times. So, administering some gentle sedation can be very helpful. Stress, anxiety and fear can increase oxygen demands, and make things harder for everybody. For gentle sedation, I like to titrate butorphanol (0.1-0.2 mg/kg IV) and midazolam (0.05-0.2 mg/kg IV).
If you have a couple moments to spare, it is helpful collect some baseline blood samples and run a couple quick, easy point of care tests. In most cases, there is a quick and easy way to collect baseline blood samples during IV catheter placement, which we demo in another video.
It is nice to run a couple quick, easy point of care tests. Minimally, I always like to run a baseline PCV/TP, lactate (“how sick are you?”) and blood glucose on emergency patients, because it usually takes less than 2 minutes to prepare these samples, and three is usually enough blood in the IV catheter stylet to get these tests started.
If you have that ability to run a very quick STAT emergency panel (with electrolytes, BUN/creatinine), great. Checking blood clotting times (PT/PTT or ACT) is also great. But in the highly compromised patient, do not delay pericardiocentesis excessively, as you may risk allowing your patient to decompensate.
A note on lactate [lactic acid] levels:
One of the first parameters I look at is the lactate level. This tells me- how sick is my patient? How badly is oxygen delivery to the tissues impaired? In my experience, the degree of hyperlactatemia tells , in my experience, corresponds the degree of compromise. Any elevation in lactate indicates that swift intervention is needed. A lactate above 6 mmol/L, and the clock is ticking. A lactate level approaching or beyond above the vicinity of 10 mmol/L is a major emergency, and immediate and appropriate intervention is required if the patient is to survive the next hour. These patients should not be put away in a kennel, but rather, should remain in the emergency treatment area as the focus of attention until they have been stabilized.
Stable means: normal heart rate, normal blood pressure, normal lactate levels.
Handheld lactate meters are priceless bedside tools. They only require a drop of blood and it is usually less than 60 seconds to results. In emergency situations, I like to recheck the lactate every 30 minutes until it is normal. Monitoring the lactate helps you assess your progress. If the lactate level is not improving continually with treatment, you should ask yourself what part of oxygen delivery you might be missing (low blood pressure, impaired oxygenation/ventilation, anemia or blood loss?)
Remember, pre-renal azotemia and electrolyte imbalance (hyponatremia, hypokalemia) are very common in these patients, and much of the time will resolve once the pericardial effusion has been addressed. Anemia and hypoproteinemia may be present, particularly in patients with acute hemorrhage into the pericardial space.
Prepare the owner:
Before the procedure, I also like to prepare the owner. I explain that there is a little sac that surrounds the heart. For some reason, fluid has accumulated in the sac, and the pressure in the sac has built up such that the heart is being squished and compressed. Because of this, the chambers of the heart cannot fill, thus preventing it from pumping blood throughout the body. This is called cardiac tamponade, and is a life-threatening emergency. To alleviate this pressure and improve circulation, we need to drain the fluid by inserting a catheter into the sac.
Now, once the fluid has been drained, further testing is still needed in order to understand the underlying cause of the fluid or “pericardial effusion.” This is extensive diagnostic testing, which may include comprehensive lab work, echocardiogram (ultrasound of the heart, preferably by a board-certified cardiologist or other highly experienced radiology professional, as some tumors on the heart can be very small and easily missed, even by experienced individuals), advanced imaging of the chest and abdomen (x-rays, abdominal ultrasound), and special tests for infectious diseases,
I prepare the owners that there are many potential causes for the fluid, and in some cases the fluid can accumulate spontaneously without any identifiable cause.
I tell the owners that in dogs, pericardial effusion is most often a manifestation of cancer, while in cats it is most often a manifestation of heart failure. In a large breed dog, there is a very good chance that this is a malignant type of cancer called hemangiosarcoma, which carries a very poor prognosis. Hemangiosarcoma tumors can be located on the heart, and can suddenly begin to bleed, causing an accumulation of blood within the pericardial sac. In these cases, alleviating the pressure and tamponade can be only temporary, because a hemangiosarcoma can bleed again in 10 minutes, 2 hours or 2 days, putting us right back at square one.
In the lucky cases, the fluid can accumulate spontaneously (idiopathic pericardial effusion), and despite extensive testing, no cause can be identified for the fluid accumulation. These cases tend to have a much better long term prognosis once the fluid has been drained. Idiopathic pericardial can also happen to middle-aged to older large breed dogs (such as Golden Retrievers).
Regardless, at this point in time, there are still a lot of cards face-down. The procedure is not without risk, and a significant financial and emotional investment is required for further testing and ongoing care, after the patient has been stabilized. In all cases, the fluid can recur in the future, and owners should be aware of this.
I inform the owners that the procedure is not without risk. Some patients can decompensate during the procedure, and complications such as cardiac arrhythmia, ongoing hemorrhage, and death can occur during the procedure or afterwards.
I also prepare the owners prior to the procedure (especially if they are going to be present), that the effusion most often looks hemorrhagic to the naked eye, even in cases of idiopathic pericardial effusion, and to not be alarmed if the fluid being drained looks like blood. That doesn’t necessarily mean that the heart itself has been punctured, nor does this confirm hemangiosarcoma.
How to Perform Pericardiocentesis : Step by Step
Prepare your supplies:
Select Site, Clip Fur, and Infuse Local Anesthetic:
Start by selecting your optimal centesis site using ultrasound. This may be on the left side or the right side, depending on the patient, and whether they have been in prolonged lateral recumbency. Theoretically, the right side should have a larger window between the lungs, but in truth, many times the left side of the chest provides better access. It just depends on the patient.
Clip the selected side generally (from approximately the 2nd rib to the 8th rib.
The centesis site is usually at the 5-6 intercostal space, mid-way between shoulder and elbow level.
I like to circle my optimal centesis site (identified by ultrasound) with a sharpie, and then infiltrate local anesthetic into that area, making sure that I go deep enough into the intercostal musculature and to minimize discomfort as I pass the catheter through the chest wall.
Scrub Site and Fenestrate Catheter:
Your assistant can then aseptically scrub the site while you put your sterile gloves on and begin to “fenestrate” the catheter. If your black circle starts to disappear, have your assistant re-mark it before a final scrub.
Fenestrate the catheter ((fenestra means window in Latin).
You will only fenestrate the distal ¼ to 1/3 of the catheter. When you fenestrate the catheter, leave the stylet
in the catheter and make small apertures or windows in the catheter so that there will be less resistance to flow. Make sure that your holes are evenly spaced and small, and that you are not leaving any burs in the catheter or compromising its integrity. You would not want any pieces of the catheter to break off inside of the patient.
Introducing The Catheter:
At the selected intercostal space, remember that you will want to advance your catheter along the cranial aspect of the caudal rib to avoid the vessels and nerves that run along the caudal aspect of the ribs. So localize this site, and then make a small stab incision into the skin using your scalpel blade, so that there will be less drag on the catheter as you pass it through the chest wall.
Grab your catheter, and remember that this is just like a gigantic IV catheter. If you look at the tip, you will notice that the metal style protrudes a couple of millimeters beyond where the actual Teflon catheter starts. You can begin to slowly advance the catheter and stylet together through the skin, and then continue creeping along the cranial aspect of the rib. If you feel a gentle scratch on the rib, that can help you gauge your depth as you are advancing the catheter into the chest cavity.
As your stylet encounters the pericardial sac, you may feel a small amount of resistance or subtle movement. As you penetrate the pericardium, you may feel a gentle pop, like you sometimes feel when you enter a vein. When you enter the pericardial sac, you will see a flash in the hub of your catheter. At this point, you will advance your stylet and catheter together a couple more millimieters, and then, holding the stylet still, feed the catheter off the stylet, the same way you would if you were feeding a catheter into a vein. As you are feeding the catheter, if you feel the catheter come into the heart (or notice VPCs on your EKG), then you can probably stop feeding the catheter, or maybe back off a little bit. Remove the stylet, and temporarily occlude the hub of the catheter while you attach the extension set. Your assistant can begin to aspirate the fluid by drawing back on the syringe. Prepare your samples for fluid analysis, and then continue draining the pericardial effusion.
When you are done, remove the catheter and place a biocclusive over the site, For the next 1-2 hours, continue to monitor the site intermittently with ultrasound for recurrence of pericardial effusion, and continue to monitor the patient’s vital parameters (heart rate, blood pressure, EKG) continuously if possible.
In the absence of complicating factors, you should see a dramatic and immediate improvement in cardiovascular parameters and strength after the procedure. Your goal is to attain normal heart rate, normal blood pressure, and normal lactate levels.
Many patients are carried into the clinic before the procedure, and experience a return of their strength and vitality after the procedure.
Analyze the fluid:
Quantify the volume you retrieved and record it in the patient’s chart.
Check the PCV/TS of the fluid, to determine whether it is a hemorrhagic or mixed hemorrhagic effusion.
If the PCV of the fluid is less than 10-15%, it would be worth while to prepare a cyto-prep of the fluid, and evaluate this under the microscope. To prepare a cyto-prep, spin sample of the effusion, draw off the supernatant, and prepare the white buffy coat onto a slide. You can also do this using standard hematocrit tubes, and using a needle to extract the buffy coat (this is usually where bacteria, white blood cells, and other type of cancer cells will be located.)
Aftercare and managing complications:
IV fluid therapy:
It may seem counterintuitive, but most of these patients actually do require intravenous fluid therapy (and not furosemide). The exception to this, of course, is those patients that that developed tamponade as a direct result of congestive heart failure (more common in cats, very uncommon in dogs).
I will usually administer IV fluids at a very conservative rate. Be mindful that over-aggressive fluid therapy in situations where there has been recent hemorrhage, can lead to a recurrence of hemorrhage. To me, a conservative fluid rate would be a 5-10 ml/kg bolus over 30 minutes followed by an anesthetic maintenance rate (10 ml/kg/h) for the first hour.
You may need to adjust your fluid therapy up or down if needed.
Ventricular premature complexes (isolated VPCs) and runs of ventricular tachycardia are relatively common, especially when the catheter touches the myocardium. If you can feel the movement of the heart muscle scratching against your catheter, then simply withdraw the catheter slightly.
If the ventricular arrhythmia is sustained for longer than a 15-30 seconds and if the patient is hypotensive (MAP<80 mmHg or systolic BP <90 mmHg), then administer lidocaine (2 mg/kg IV over one minute); this may be repeated to a maximum dose of 8 mg/kg within a 10 minute period. If the arrhythmia recurs within 20-30 minutes, you may need to treat it again as before, and then may consider initiating a continuous rate infusion (CRI) of lidocaine (40-80mcg/kg/min) for ongoing control, which ideally can then gradually be tapered down.
If I feel that I have adequately drained the fluid from the pericardial sac, but notice that it is filling up again quickly, to me this indicates ongoing hemorrhage. Sometimes by relieving the mechanical pressure on the source of hemorrhage, bleeding can start up again.
Start by checking blood clotting times. If these are significantly prolonged, fresh frozen plasma will likely be needed to restore clotting factors. Many patients with significant ongoing hemorrhage will develop a consumptive coagulopathy, where clotting factors are consumed so that the blood can no longer clot effectively. With active hemorrhage and prolonged clotting times, the bleeding will probably not stop until the coagulopathy has been addressed.
Accumulating blood in the pericardial space resulting from ongoing hemorrhage can be collected and administered back to the patient using a technique called autotransfusion (click here to learn how to perform autotransfusion).
Autotransfusion can be used to maintain patient stability, while waiting for a clot to form, for the hemorrhage to resolve, or for the site of hemorrhage to be addressed surgically. I think of ongoing hemorrhage like a fish tank with a hole in it. If all the water drains out, all of the fish will die. Autotransfusion is like collecting the water coming out of the hole, and pouring it back into the tank, so that the water level in the tank remains stable. Obviously, if the hole doesn’t get patched (if the bleeding doesn’t stop), then you will be there all day.
When significant hemorrhagic effusion and active hemorrhage is present, it is a smart move to transfer blood retrieved via pericardiocentesis directly into a blood collection/blood administration bag, so that it can be administered back to the patient through a filtered blood administration set.
Continued hypotension, lack of cardiovascular stability:
In situations where the blood pressure is very low, a different approach may be needed, such as more aggressive fluid therapy, vasopressor therapy, or continued investigation into the cause of ongoing hypotension (septic pericarditis, etc.)
Laceration or puncture of the lung resulting in pneumothorax is uncommon. If this happens and the degree of pneumothorax is clinically significant, you can alleviate the pneumothorax by performing thoracocentesis.
1 J Am Vet Med Assoc. 2013 Jul 15;243(2):232-5. doi: 10.2460/javma.243.2.232.