Page 117 - Clinical Manual of Small Animal Endosurgery

Diagnostic Laparoscopy 105

Anaesthetic considerations

Laparoscopy is usually performed under general anaesthesia. Special
anaesthetic considerations and complete understanding of the physiolog-
ical changes caused by abdominal insufflation and patient position are
necessary to minimise potential complications related to anaesthesia.
Patients should be thoroughly examined before undergoing general
anaesthesia, and appropriate tests performed (complete blood count,
biochemistry panel including electrolytes, urinalysis and other tests as
necessary). Any dehydration or acid–base abnormalities should be cor-
rected before the procedure, and the anaesthetic protocol should be
individually tailored.
Current recommendation for animals undergoing general anaesthesia
is that food should be withheld for 6 h in adult dogs (for shorter periods
in immature animals), and water for 1 h before anaesthesia (Savvas
et al., 2009). The nutritional status of the patient should be taken into
account, and the insertion of a feeding tube anticipated.
A dedicated member of the team should be available to monitor the
patient throughout the procedure; pulse oximetry, capnography and
electrocardiography (ECG), together with an oesophageal stethoscope,
should be used for assessing normal physiological parameters. Patients
in critical conditions will benefit from invasive blood-pressure mon-
itoring; this will also consent easy blood-gas sampling. Non-invasive
methods, such as Doppler or oscillometric monitors, are sufficient for
elective procedures. Mean arterial pressure should be maintained higher
than 60 mmHg in small animal patients.
Crystalloid fluids should be administered to patients undergoing
general anaesthesia, regardless of the anticipated amount of blood loss,
as inhalant anaesthetics cause vasodilation and decreased venous return.
Administration of colloids may be beneficial in selected cases.
In particular, induction with barbiturates is best avoided for laparos-
copy, because of induced splenomegaly and consequent increased risk of
splenic puncture. Nitrous oxide should not be used during procedures
in which there is the risk of pneumothorax.
Hypothermia may also occur during laparoscopy, especially in small
patients, as the insufflation gas is below room temperature and of low
humidity, both of which cause significant patient cooling. Monitoring of
patient’s temperature and use of heating devices are important, particu-
larly in long procedures.
Another important consideration is related to the increased intra-
abdominal pressure consequent to insufflation, which compresses the
vena cava, depressing venous return. The degree of haemodynamic
change depends on the animal’s intravascular volume, with more severe
hypotension in hypovolaemic animals. Increased intra-abdominal pres-
sure also causes cranial displacement of the diaphragm, which will
decrease tidal volume and encourage atelectasis with associated increase