Page 27 - Clinical Manual of Small Animal Endosurgery

Rigid Endoscopy 15

introduction, the gas insufflation tubing is attached to the cannula via a
Luer-lock extension to maintain pneumoperitoneum during the proce-
dure. The carbon dioxide should be infused via an automatic regulating
device (insufflator), which controls abdominal pressure, gas flow rate
and total volume of gas delivered. Automatic insufflation is another
feature of insufflators: the intra-abdominal pressure is set at a predeter-
mined value, and the device insufflates gas if the pressure within the
abdominal cavity falls below it. The intra-abdominal pressure should not
exceed 12–13 mmHg in cats and 13–15 mmHg in dogs: higher abdominal
pressures decrease venous return and reduce ventilating ability. The
carbon dioxide flow rate can usually be regulated to between 1 and 20 L/
min in 0.1 L increments.
A filter is placed at the outlet of the insufflator to provide microbio-
logical filtration of the insufflating gas and to prevent retrograde con-
tamination of the machine. Such filters are disposable and intended for
single use, although they are commonly used repeatedly in veterinary
surgery, unless soiled. An insufflation hose connects the insufflator to the
patient (via trocar or Veress needle).

Veress needles
Veress needles are the most common type of insufflation needle and can
be disposable or reusable (Fig. 1.15). Although disposable needles are
always sharp, their cost usually precludes their use in veterinary medi-
cine; as with other disposable items they could be re-sterilised a number
of times. However, this would cause loss of sharpness and therefore
defeat the purpose of their use. Veress needles have a spring-loaded
obturator that retracts when the needle is in contact with tissues. When
the needle enters the abdomen, the pressure on the tip is released, and

Fig. 1.15 A reusable Veress needle suitable for establishing
pneumoperitoneum by the closed technique.