Page 199 - Clinical Manual of Small Animal Endosurgery

Thoracoscopy 187

If the pericardial effusion has not been at least partially drained preop-
eratively then a thoracoscopic guided pericardiocentesis is usually needed
to allow the pericardium to be grasped and incised. This may be per-
formed with a spinal needle inserted percutaneously, or via a port with
a dedicated endoscopic needle. The pericardium is often notably thicker than
normal: this should be borne in mind if practising the procedure on cadav-
ers. The sternopericardial ligament and ventral mediastinum may also be
thickened, with tortuous vessels that require bipolar cautery before section-
ing. If only a pericardium window is performed, the ligament does not need
to be sectioned, and a small fenestration is simply made for instrument
insertion. For subtotal pericardiectomy, the sternopericardial ligament
should be resected ventrally and close to the sternum, otherwise a curtain
of mediastinum interferes with instruments and tends to splatter the endo-
scope end, which then needs to be repeatedly cleaned (Fig. 6.10).
When performing a partial (window) pericardiectomy, a window is
cut in the ventral/lateral pericardium, avoiding the right atrial appendage
cranially (Fig. 6.11), which could be inadvertently cut with potentially
catastrophic results. Potter and Hendrickson (1999) describe the success-
ful use of extracorporeal suture loops to repair accidental trauma to the
right atrial appendage during thoracoscopic pericardiectomies in dogs.
Suture loops have also been used to perform a palliative resection of a
pedunculated atrial haemangiosarcoma in a similar manner (Crumbaker
et al., 2010) (Fig. 6.12). Care also needs to be taken not to inadvertently
cut lung tissue during ventilation, which may need to be periodically
stopped for brief periods during parts of the pericardiectomy (Fig. 6.13).
The window needs to be a sufficient size not to simply adhere closed,
but not so large that the heart can herniate. Adhesions may be present
between the pericardium and epicardium in some areas, and these should
be sectioned with care if possible, or another region of pericardium
removed. Once an initial incision in the pericardium has been made, a
palpation probe may be inserted to investigate the presence of adhesions.
If only a pericardial window is performed this may be expanded by
making two or three longitudinal incisions or fenestrations just ventral
to the phrenic nerves (Radlinsky, 2008). The removed section of pericar-
dium should always be submitted for histopathology, as well as micro-
biology if indicated.
Subtotal (subphrenic) pericardiectomy (Fig. 6.14) is more time-
consuming and technically slightly more difficult, but is indicated in
conditions such as restrictive (fibrous) pericarditis (Fig. 6.15) and infec-
tious pericarditis. Anecdotally it also appears to result in better palliation
in cases of neoplasia. Subtotal pericardiectomy is started the same as for
a partial (window) pericardiectomy in dorsal recumbency, but a fourth
port may be required, as described above. The ventral mediastinum is
completely resected at the ventral aspect, with the aid of bipolar cautery
or an ultrasonic scalpel.
After the initial incision, it is advisable to briefly explore the pericar-
dial space with a blunt palpation probe for adhesions. Large significant