Page 192 - Clinical Manual of Small Animal Endosurgery

180 Clinical Manual of Small Animal Endosurgery

prepared loops, and is reliable for lung biopsies and ligations with both
monofilament and braided synthetic suture materials. The Weston knot
is another popular extracorporeally tied endosurgical slip knot, but
although less bulky and relatively easier to tie it has a much lower knot
strength than the Meltzer knot (Sharp et al., 1996).
It does take some practice to become familiar with forming and utilis-
ing the Meltzer knot. While this knot can be formed and reliably used
with monofilament sutures, it is easiest to prepare and use when made
with braided suture materials such as polyglactin 910 (Vicryl, Ethicon;
Polysorb, Tyco), which have less memory. It is also possible to pre-
prepare several loops and sterilise them so they are ready for use in
surgery. Trostle et al. (2002) demonstrated that ethylene oxide sterilisa-
tion of pre-tied monofilament polydioxanone suture loops did not have
any adverse effect on suture failure strength. Small peripheral lung biop-
sies provide an ideal situation for becoming proficient with their use (see
below), and it is markedly less costly than using an endoscopic stapler.
The standard open-ended or notched knot pushers most commonly
offered by veterinary endosurgical suppliers are poorly suited to precise knot
placement, loop manipulation and adequate tightening. A closed-ended
knot pusher (with a hole at the distal end) is preferable, allowing precise
knot positioning as well as application of a tight-locked knot under tension.

Intracorporeal suturing and ligation
Internal suturing and knot tying are more difficult than extracorporeal
knot tying, and currently of limited application in veterinary thoracic
endosurgery. Application for the thoracoscopic repair of some diaphrag-
matic hernias, as in humans, does currently warrant further investiga-
tion, and may be aided by the use of disposable suturing devices such as
the Endo Stitch applicator (Covidien), rather than endosurgical needle
holders and J-shaped endoski needles. Intracorporeal tying of ligatures
is seldom indicated in thoracoscopy. Not only is the increased technical
difficulty and limited space disadvantageous, but more importantly it is
difficult to apply adequate tension to ligate any but the smallest vascular
structures (Fig. 6.7). While dedicated 5 mm and even 3 mm paediatric
needle holders are available, grasping forceps with locking handles are
equally suitable for simply tying intracorporeal ligatures. Andrews and
Lewis (1994) investigated the use of endoscopic haemostatic clips as an
alternative to knotting, for securing untied suture ends, but found this
to be significantly weaker than knots, and their use for this purpose is
hence not recommended.

Anaesthesia

General anaesthesia is required for thoracoscopic procedures. Preopera-
tive assessment, anaesthetic preparation and monitoring requirements are
essentially the same as for traditional open-chest surgical procedures.