Pericardiocentesis should be performed. Dogs with cardiac tamponade may need intravenous fluid support, diuretics are contraindicated.
If there was no mass noted during the work-up, then the case is monitored to see whether pericardial effusion recurs. Approximately
50 percent of IPE cases may resolve after one or two pericardial taps. If the effusion forms again, repeat taps can be performed,
but after three episodes surgical options are considered. If IPE is confirmed, then partial pericardectomy is potentially
curative. If an intrapericardial mass was noted on the right atrium or right atrial appendage, it is most likely a hemangiosarcoma.
A proximal aortic mass (heart-base mass) without right atrial involvement is most likely a chemodectoma. Partial pericardectomy
can be considered in chemodectoma cases; a medial survival of 730 days post-partial pericardecomy has been reported. Removal
of a chemodectoma is usually not possible since they are generally locally extensive at the time of diagnosis. Hemangiosarcoma
has a worse prognosis even if thoracotomy is performed with surgical debulking of the mass and follow-up chemotherapy.
The dog has a brief repeat echocardiogram on the day of surgery prior to the induction of anesthesia. If significant pericardial
fluid is present, some is removed by pericardiocentesis to reduce cardiac compromise under anesthesia. A small amount of
pericardial effusion is not a problem and actually aids picking up the pericardium intraoperatively. Anesthesia is induced
using a cardiovascular sparing protocol, and the patient is closely monitored throughout, including measurement of blood pressure,
electrocardiogram, pulse oximetry and end tidal CO2.
Photo 2: The pericardium has been grasped and lifted ready for the first cut.
Partial pericardectomy can be performed via an open intercostal or median sternotomy approach, or via thoracoscopy. Thoracoscopic
partial pericardectomy has advantages over an open thoracotomy approach since it results in less postoperative pain, fewer
wound complications and a quicker return to function. Hospital stays are shorter, and client costs are usually lower. Disadvantages
of thoracoscopy include the need for special equipment. In addition, it is often not possible to biopsy a mass via the scope
without risk of hemorrhage, and visualization dorsal to the heart is limited. Thoracoscopy involves the use of a monitor,
camera, light source, cautery, trochars and thoracoscopic instruments. Intermittent positive pressure ventilation is required,
and a primary and assistant surgeon are needed to perform the procedure.
The patient is placed in dorsal recumbency and rolled slightly to the right side. A wide area is clipped and prepared for
surgery. The owner is always made aware that, should the need arise, conversion to a median sternotomy approach will be made.
Usually three ports suffice for the procedure, but additional ports can easily be placed if needed. Selective intubation of
the right main bronchus can be performed but is not necessary. A trochar is placed in the paraxiphoid transdiaphragmatic position,
directed into the left hemithorax. The camera is placed into this port and the left hemithorax is visualized.