Page 29 - Clinical Manual of Small Animal Endosurgery

Rigid Endoscopy 17

Laparoscopic instruments

Virtually all surgical instruments are available in a laparoscopic version
(grasping forceps, scissors, retractors and needle holders, for example).
An additional instrument is the palpation probe. This is a blunt metal
calibrated probe used as a finger to ‘palpate’ or move organs. The probe
is marked at 1 cm intervals, allowing for accurate measurement of organs
or lesions, which is otherwise difficult in the presence of magnification.

Energy sources

Haemostasis is a critical step in minimally invasive surgery, as even minor
haemorrhages have a detrimental effect on surgical performance. During
video-assisted surgery the presence of blood in the surgical field not only
obscures the organs but absorbs light, resulting in loss of image quality.
It can also be difficult to remove from the site. For this reason, as well
as minimising blood loss, haemostasis is critical for these surgeries.
Although numerous modalities are available to achieve haemostasis,
energy-assisted devices such as electrosurgical units, lasers and ultrasonic
cutting/coagulating appliances are usually preferred. All these devices
have been shown to significantly decrease surgical time (Mayhew and
Brown, 2007).
Energy sources are also used for tissue debridement and capsule
shrinkage in arthroscopy, and for lithotripsy in cystoscopy.

Electrosurgery
Electrosurgical modalities are the most commonly used energy sources,
since they are the most economical. These entail the use of an alternating
current passing through the patient to complete the circuit. In monopolar
electrosurgery, the current flows from the active electrode (in the hand-
piece) through the patient towards the passive electrode (grounding pad),
whereas in bipolar devices both the active and return electrodes are
housed in the handpiece.
Monopolar applications are less safe during rigid endoscopy than
bipolar ones, because as current flow follows the path of least resistance,
coupling can occur when the electrosurgical tip comes into contact
with the scope or other instruments outside the field of view. Similarly,
insulation defects and sparking can cause damage to adjacent tissues.
These injuries are usually outside the surgical field of view, increasing
the hazard. Monopolar electrosurgery also causes the generation of
more aerosolised particles (smoke or plume) than bipolar surgery; this
plume is a potential hazard to operating-room personnel and also
obscures the surgical field. Monopolar electrosurgery can only be used
in a non-conducting medium. Therefore it can be used during laparos-
copy and thoracoscopy but cannot be used during fluid instillation (e.g.