Notes supplied by Nadja Sigrist, DrMedVet, FVH(Small Animals), DACVECC.

Introduction

Pericardiocentesis is used to eliminate pericardial effusion from various causes. Pericardial effusion is defined as excess, abnormal fluid between the pericardial sac and the heart. The increased intrapericardial pressure associated with fluid accumulation will impair cardiac filling, leading to decreased cardiac output, systemic venous congestion and right heart tamponade. Animals present with weakness or collapse, poor pulse quality or pulsus paradoxus, distended jugular veins and ascites, and often have a history of an episode of vomiting. Diagnosis of pericardial effusion is made by echocardiography and/or thoracic radiographs.

Indications for Pericardiocentesis

Pericardiocentesis is indicated as an emergency procedure in patients with cardiac tamponade. In some cases the fluid can be used diagnostically by looking at predominant cells in the effusion (e.g., lymphocytes vs. mesothelial cells vs. blood). Pericardial effusion may be idiopathic, haemorrhagic (trauma, coagulopathy, haemangiosarcoma, atrial tear), neoplastic (mesothelioma, lymphoma) or infectious. Pericardiocentesis in animals with a possible haemorrhagic effusion should be carried out only in patients with signs of shock or tamponade and coagulopathies should be treated concomitantly to avoid continuous bleeding.

Equipment

The following equipment should be prepared (sterile) in advance:

 Clippers and disinfectant

 Sterile drapes

 Sterile gloves

 Electrocardiogram (ECG)

 Ultrasound machine if available

 Large intravenous catheter (10–14-gauge, 10–15 cm for large dogs; 16–18-gauge, 4–6 cm for small dogs and cats)

 Extension set (30–50 cm) connected to three-way stopcock and syringe

 Collection container

 Sampling tubes (serum, EDTA, culture)

 Lidocaine 2%

Patient Preparation

Pericardiocentesis is a sterile procedure. Lateral recumbency allows for best restraint; however, some animals may require centesis performed in sternal recumbency. Pericardiocentesis is commonly performed from the right side to avoid injury to the lungs and carotid arteries. Left-sided pericardiocentesis allows better differentiation between blood from effusion versus blood from incidental puncture of the left ventricle, since blood from the left ventricle will be freshly oxygenated and brighter than the blood contained in the effusion.

Depending on the cardiovascular status and temperament of the animal, sedation is recommended. Butorphanol 0.2 mg/kg i.v. +/- acepromacine 0.005 mg/kg i.v. or midazolam 0.2 mg/kg generally works well without interfering with cardiovascular performance.

Patients should be monitored with at least a continuous ECG. A bolus of 2 mg/kg lidocaine should be prepared in case of severe ventricular tachycardia during centesis.

Technique

Pericardiocentesis can be performed under ultrasound guidance or blind. Blind puncture is recommended between the third and fifth right ventral intercostal space while ultrasound-guided pericardiocentesis is performed at the location that identified the largest diameter of effusion.

1.  The skin is shaved and surgically prepared over the second to the eighth intercostal spaces and from the sternum to mid-chest.

2.  Sterile gloves are worn, the site may be draped and the intravenous catheter, extension set with three-way stopcock and syringe are prepared in a sterile fashion.

3.  A local block with 2% lidocaine is placed including skin, intercostal muscle and pleura.

4.  When a large catheter is used, a small stab incision in the skin may facilitate catheter placement.

5.  The puncture site should be in the middle of the intercostal space to avoid the intercostal vessels.

6.  The intravenous catheter is advanced slowly and perpendicular to the skin through the skin, intercostal muscle and pleura into the pericardial sac. The pericardial sac is reached when a loss of resistance is felt and (often sanguineous) fluid can be seen at the catheter hub. With concurrent pleural effusion, fluid (usually straw-coloured) will already be seen when the needle enters the pleural space.

7.  The catheter is advanced slightly more over the stylet followed by removal of the stylet and connection of the collecting system. Aspiration of fluid is performed by an assistant while the operator holds the catheter in place.

8.  Samples are saved (ETDA for cytology, serum for bacterial culture) and as much fluid as possible is drained.

9.  If the operator feels a scratching or tapping sensation the catheter is in contact with the heart and should be retracted slightly.

10.  Once no more fluid can be aspirated the catheter is retrieved.

Alternatively, a small pericardiocentesis catheter or central venous catheter can be placed using the Seldinger method. This technique allows for continued fluid aspiration.

Complications

If performed correctly, pericardiocentesis is a relatively safe procedure. The most common complication is ventricular premature beats or ventricular tachycardia from myocardial injury by the catheter. Other, less common complications are coronary artery laceration, ventricular puncture, pneumothorax or continuous bleeding.

Recurrence of pericardial effusion is common and may occur within hours (ruptured haemangiosarcoma) or after weeks (idiopathic).