The accumulation of fluid in the abdomen or lungs makes it more difficult for the animal to exercise, as they are not able to inhale or exhale efficiently. As a result, the animal is more at risk of acute collapse episodes [ 8 ]. As mentioned earlier, a lot of these clinical signs can be seen with other presentations( both emergency and non-emergency) and so diagnostic imaging should be performed promptly to help reach a diagnosis before any procedure is carried out.
The role of the veterinary nurse
Pericardial effusion and subsequent cardiac tamponade are an emergency, and the veterinary team must work without delay to give the animal the best chance of survival. Preparation is vital to relieve the patient from the stress and pressure their body is under as quickly as possible. It is useful to have pre-assembled kits for pericardiocentesis, as well as other emergency situations, to reduce the set-up time. As soon as the practice has been notified of the patient ' s imminent arrival, full-team communication will be essential. This will allow the veterinary nurse( VN) to set up the equipment needed to carry out the procedure before the patient arrives at the practice and a diagnosis is made [ 9 ]. It is never frowned upon to be over-prepared for any potential emergency.
The equipment required for pericardiocentesis is as follows:
• Clean clippers
• Surgical scrub( 0.05 % chlorhexidine)
• Sterile gloves
• Scalpel blade
• 14 – 18 G catheter
• Three-way tap
• Large syringes( suitable for the size of the patient)
• EDTA and plain blood tubes
• Local anaesthetic
• Needle and syringe for the local anaesthetic
• Monitoring equipment – pulse oximeter, blood pressure monitor, ECG monitor, ultrasound machine
As pericardiocentesis can be done in the conscious animal, patient advocacy should be at the forefront of the VN ' s priority list. An intravenous catheter should be placed as quickly and in as stress-free a manner as possible.
Adequate analgesia must be administered, under the veterinary surgeon ' s( VS ' s) instruction, and local nerve blocks should be used as part of the care plan to optimise patient comfort [ 10 ]. Continually checking for pain responses throughout the procedure is crucial, and the VN should not hesitate to inform the VS if they think the animal requires additional pain relief, as patient welfare is paramount.
Providing O 2 via nasal prongs( if tolerated by the patient) or the flow-by method throughout the procedure is extremely important. As the patient ' s body is already working hard to transport the limited available O 2 to the tissues, supplementation will reduce this effort [ 11 ]. The O 2 saturation of the blood should be checked with a pulse oximeter, to establish a peripheral oxygen saturation( SpO 2
) value during the process. Alternatively,
SpO 2 can be assessed more accurately by arterial blood gas analysis.
The patient ' s BP should also be monitored throughout the process. Due to the strain on the heart, and the subsequent reductions in stroke volume and cardiac output, the vasodilation of the vessels will produce a hypotensive reading [ 12 ]. As the fluid is removed from the pericardial sac, reducing the burden on the heart, the BP should gradually increase until the patient is normotensive. It is important that the VN notes any findings to the VS before, during and after the procedure so a suitable care plan can be made.
Possible complications
Although the incision site for pericardiocentesis is small, there is still a risk of a surgical site infection( SSI). Due to the location of the procedure, any potential bacterium has free access to enter the bloodstream and can spread rapidly via the now effectively beating heart [ 13 ]. In order to lessen the risk of SSIs, the animal should be clipped around the fifth or sixth intercostal area and surgically scrubbed, and strict sterility protocols should be followed before a needle is inserted [ 14 ].
As the procedure involves placing a needle close to the heart and can be done in the conscious animal, the most obvious complication is puncturing the heart itself, causing haemopericardium, leading to sudden death [ 15 ]. Ultrasonography can be used to assist the VS with the procedure, hence the importance of setting this up prior to the arrival of the patient [ 1 ]. The number of people in the room should be kept to the necessary minimum, to limit the movement of, and any potential additional stress to, the animal.
Another complication that may arise is the presence of cardiac arrhythmias, so the patient should be connected to an ECG monitor to assess the efficacy of the draining of the effusion and to monitor for the development of abnormal heart traces. This will allow the team to see the morphology of the P and T waves, as well as the QRS complexes, and if( or how) they differ before, during and after the procedure. If the VS has placed the needle too close to the myocardium, arrhythmias such as ventricular premature contractions( VPCs) may develop( Figure 2, page 45) [ 16 ]; if this occurs, the catheter should be removed immediately [ 17 ]. The VN should alert the VS if any abnormalities are seen or if they are at all concerned.
44 Veterinary Nursing Journal