Page 203 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery

Pericardial diseases Pericardial surgery
The indications for pericardial surgery include incision, to
VetBooks.ir The pericardium is continuous with the mediastinum and allow access to the heart for surgical manipulation, and
consists of a dense fibrous pericardial sac, which is
excision (subtotal pericardectomy) to treat a range of
covered by mesothelium on its pleural and parietal sur-
conditions including neoplastic and idiopathic pericardial
faces. The pericardial sac normally contains a small vol-
ume of fluid that lubricates the surfaces of the parietal effusions, bacterial pericarditis and chylothorax. Subtotal
pericardectomy, the removal of as much pericardium as
serous pericardium and the visceral serous pericardium
is reasonably achievable, can be done via a left or right
(epicardium). Because of the dense fibrous tissue in the thoracotomy, via median sternotomy or thoracoscopically.
pericardium, it is relatively inelastic, although it can
Selecting the correct patient for pericardial surgery and
become ‘stretched’ over time, as is seen in dogs with
matching that patient with the correct technique is the first
chronic pericardial effusion. As mentioned above, a tube step to minimizing both disease-related and technical
of epicardium traverses the base of the heart caudal to
complications. For example, dogs suspected to be suffer-
the aorta and the pulmonary artery, the transverse peri-
ing from bacterial infective pericarditis are probably best
cardial sinus, which creates a direct communication treated by open thoracic exploration and pericardectomy,
between the two sides of the pericardial sac. This feature
to maximize the ability of the surgeon to identify any under-
can assist placement of a TCOO clamp (see earlier).
lying cause (e.g. foreign body) and optimize the debride-
ment of infected and diseased tissue whilst minimizing the
Clinical features of pericardial disease risk of iatrogenic phrenic nerve injury. Alternatively, a dog
with suspected right atrial haemangiosarcoma may be best
Cardiac tamponade is the term used to describe the detri- approached via a right fifth inter costal thoracotomy to facil-
mental effect of increased intrapericardial pressure on itate complete assessment of the right atrium. Finally, an
heart chamber filling and, therefore, on ventricular ejec-
aged dog with a presumptive chemodectoma at the heart
tion. Such an increase in intrapericardial pressure can base causing pericardial effusion may be palliated suffi-
result from an abnormal volume of pericardial fluid or
ciently by the minimally invasive creation of a pericardial
secondary to fibrous ‘restrictive’ pericardial disease.
window, whereas the same procedure may be inferior for
Permanent relief from tamponade is typically a key goal of the treatment of idiopathic pericardial effusion. Because of
pericardial surgery. Clinically, animals in tamponade will be
the difficulty in achieving a definitive diagnosis, it is recom-
presented because of signs associated with right-sided
mended that any pericardium removed is submitted for
heart failure such as exercise intolerance and ascites. microscopic examination, along with pleural biopsy mat-
Physical examination can reveal tachycardia, muffled heart
erial and sternal lymph node biopsy specimens.
sounds, a consistent variation in peripheral arterial pulse
quality associated with the different phases of respiration
(pulsus paradoxus), jugular distension with pulsation, Open subtotal pericardectomy
hepatomegaly and free peritoneal fluid. Although a tran- This is best performed via a left or right fifth intercostal
sient increase in pericardial fluid can accompany many thoracotomy or median sternotomy. Release of pericardial
disease processes (viral infections, trauma, anticoagulant fluid can cause significant haemodynamic improvement
intoxication), most commonly tamponade is caused by the and should be done as soon as possible once the chest
effusion associated with heart-base tumours, idiopathic cavity is open, and the anaesthetist should be made aware
pericardial disease and, occasionally, bacterial infective when this is happening. Usually, it is possible to elevate
pericarditis. In addition, haemorrhage from a bleeding the phrenic nerve gently from the pericardium and protect
tumour (e.g. right atrial haemangiosarcoma), or from a this structure using a silicone vessel loop or Penrose drain,
‘tear’ in the left atrial wall secondary to degenerative mitral at least on the side of the thoracotomy, thus allowing the
valve disease, can cause either a gradual or an acute pericardial resection to be carried out close to the dorsal
increase in intrapericardial pressure, resulting in tamp- pericardial reflection. Once the phrenic nerve has been
onade. The diagnosis can be confirmed most rapidly using elevated, the pericardium is incised parallel to the heart
cardiac ultrasonography. Once the patient is stable, a base and the incision is continued towards the heart apex
thorough investigation should be undertaken in an attempt to form a T-shaped incision. Stay sutures in the pericardial
to identify an underlying cause for the effusion along with edges will help with these manipulations, and the incision
any concurrent disease processes. in the often quite vascular pericardium can be made using
electrosurgery or a harmonic instrument to aid haemo-
Patient stabilization stasis, providing the myocardium and phrenic nerve are
well protected. The incision around the base of the heart is
Short-term relief of cardiac tamponade secondary to continued either above or below the level of the phrenic
increased pericardial fluid volume can be achieved by nerve, depending on whether it has been mobilized, on the
pericardiocentesis. This technique involves draining the contralateral side of the heart.
pericardium using a needle or catheter, via a right lateral These manipulations may require temporary displace-
thoracic approach (fifth intercostal space). Ultrasound ment of the heart and can cause a significant temporary
guidance is ideal, and local anaesthetic infiltration of the reduction in venous return and systemic blood pressure.
skin and full aseptic technique should be used in all but The anaesthetist should also be made aware when the
the most urgent circumstances. Intermediate-term relief of heart is being manipulated in such a way and it may be
tamponade can be achieved using a Seldinger technique necessary to perform this part of the resection in ‘stages’
to place a short-term indwelling catheter or to facilitate if severe hypotension develops. Completing the pericardial
balloon dilation of the pericardial ‘hole’ to allow prolonged incision from ‘inside’ the pericardium will prevent the
drainage. Typically, needle holes and balloon holes seal surgeon inadvertently wandering into the mediastinal
over time. (See the BSAVA Guide to Procedures in Small adipose tissue (which can be voluminous) and damaging
Animal Practice.) other structures therein. Once the heart base incision

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