Page 206 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 15 · Surgery of the heart, pericardium and great vessels

left recurrent laryngeal nerve is identified as it leaves the ductus should help the surgeon gain a good understand-
left vagus and travels caudal to the PDA so as to avoid ing of the dimensions of the ductus and allow gentle pas-
VetBooks.ir bile duct forceps) is then used to dissect around the aorta mosquito forceps, as appropriate) either from cranial to
sage of a dissection instrument (usually Mixter or Halsted
inadvertent damage.
A right-angled dissection instrument (Mixter or Lahey
caudal or caudal to cranial, at an appropriate level to
caudal to the ductus but cranial to the first intercostal
artery. Either moist umbilical tape or a 6.4 mm (¼ inch) complete the ductus dissection (Figure 15.4d). Once dis-
section is complete, the author prefers to pass two appro-
Penrose drain, or a silicone vessel loop (depending on the priately sized surgical silk sutures around the ductus,
size of the animal) is placed loosely around the aorta and along with one fine (1 metric (5/0 USP)) polypropylene
secured with artery forceps. Using gentle traction on this suture (Figure 15.4e). The silk suture on the aortic side is
aortic noose, the space caudal to the ductus between the tied first, with the aim of arresting blood flow through the
aorta, ductus and pulmonary artery trunk can be opened ductus and abolishing the machinery murmur. Next, the
and extended medially by gentle dissection under direct polypropylene suture is tied and finally the silk suture on
visualization (Figure 15.4ab). This dissection is done first the pulmonary artery side is tied (Figure 15.4f). Frequently,
because it provides access for the placement of straight abolition of blood flow through the ductus is associated
ductus clamps, should haemorrhage develop during with an acute increase in diastolic blood pressure and,
future dissection. Cranial to the ductus, the space therefore, mean blood pressure; this increased ‘afterload’
between the aortic wall and the ductus can be opened by is sensed by baroreceptors in the aortic wall, which in
gentle dissection (Figure 15.4c). In very small animals this turn trigger a bradycardic response (Branham sign). This
dissection does not always remain extrapericardial but in is typically short-lived and rarely requires treatment,
larger animals it should. The preparation caudal to the although it can be temporarily disconcerting.

a The vie of the heart and
15.4
pericardium via a left fourth
intercostal thoracotomy in a 1.4 kg dog
with patent ductus arteriosus. With a
vessel loop around the vagus nerve (V)
and one around the aorta (Ao), the
ductus arteriosus (D) is apparent. With
gentle dorsal traction on the aorta, the
dissection plane caudal to the ductus is
made obvious (arrowed).
pulmonary artery trunk. b This
dissection can be developed gently
using a Mixter (M) or Halsted mosquito
forceps as appropriate. c The
dissection plane between the cranial
(a) (b) ductus and the aorta is identified by a
‘crease’ in the overlying mediastinum.
This plane is gently developed using
i ter or alsted mos uito forceps
as appropriate. d The dissection
around the ductus was completed using
mos uito forceps in this small dog.
e f T o sutures of surgical silk and
one fine polypropylene suture are
passed around the ductus and tied.

(c) (d)

(e) f

197

Ch15 HNT.indd 197 31/08/2018 13:26