Page 190 - Clinical Manual of Small Animal Endosurgery

178 Clinical Manual of Small Animal Endosurgery

the current path confined to tissue grasped between the instrument tips.
This modality also works well in irrigated environments or when haem-
orrhaging has occurred. A small gap needs to be maintained between the
instrument tips for cautery to function. If bipolar forceps fail to function
during a procedure it is often the tips that have bent and are touching
each other directly, resulting in a short circuit and no cautery. Opening
the tips slightly usually results in a return of function.

Tissue feedback controlled bipolar surgery
Handpieces are available in 5 and 10 mm diameters, with an integrated
blade, allowing one to seal and cut tissue without having to change
instruments, hence shortening surgery time. Examples are LigaSure,
made by Valleylab, and Enseal, by Ethicon. The tool can be used to seal
blood vessels up to 7 mm in diameter, and it may be suitable for taking
peripheral lung biopsies (see below). The control unit measures tissue
impedance and gives an audible signal once tissue has been sealed. This
also prevents overlong application with char formation leading to an
increased inflammatory response. The main disadvantage of this system
is that the instruments are single-use, disposable and relatively expensive,
adding to the costs of veterinary thoracoscopic procedures. Whereas
handpieces are commonly reused and re-sterilised by liquid or ethylene
oxide sterilisation, they can be difficult to clean, and only suitable for
very limited reuse. Some surgeons do not favour them, as the jaws can
become sticky with coagulum during surgery, and laparoscopic clip
applicators are generally favoured for haemostasis of important vascular
structures in human surgery.

Ultrasonic scalpel
Unlike electrosurgery, this modality uses an ultrasound transducer
in the handpiece to transmit vibrations down the shaft of the instru-
ments to the tip. This generates heat, which coagulates vessels in a
similar way to electrosurgery, but with none of the electrosurgical risk.
Examples include Harmonic ACE (Ethicon), AutoSonix (Covidien)
and Sonosurg (Olympus). Ultrasonic scalpels are regarded as effec-
tively sealing vessels up to 3 mm in diameter. They generate less heat
than standard electrosurgery, with minimal collateral heat propaga-
tion, and are useful for dissection around delicate structures. Unfor-
tunately, as with tissue feedback controlled bipolar surgery, they also
utilise expensive single-use handpieces that add to veterinary proce-
dure costs (with the exception of the Olympus Sonosurg system, which
has reusable handpieces). They are similarly difficult to clean, and
have a limited lifespan if reused and re-sterilised by liquid immersion
or ethylene oxide gas.