Page 74 - BSAVA Guide to Pain Management in Small Animal Practice

5 | Pharmacological treatment of pain

VetBooks.ir Clinical use: cycle’ in animals experiencing chronic pain and
hyperaesthesia. ptions include a one o
Sedation and anaesthesia induction: If used as
part of the sedation or induction protocol prior to
dose of ketamine . mg kg , or admitting the
painful procedures, ketamine probably subcutaneous or intravenous injection of a low
contributes signi cantly to analgesia and helps animal for a day to administer a low-dose
prevent central sensitization. Ketamine intravenous ketamine infusion.
(combined with a benzodiazepine) can be a
good choice for trauma patients because of its Amantadine
bene cial cardiorespiratory and analgesic Amantadine is an NMDA receptor antagonist
properties, but it is not usually recommended available as an oral capsule or syrup, which
for head trauma patients. It should be avoided in can be administered at home by owners. It may
patients with intracranial disease, hypertrophic be useful for treating chronic pain. Research
cardiomyopathy, or severe ocular trauma. is limited, but the recommended dose is
mg kg 4h in dogs and cats Siao et al., 11;
Intraoperative analgesia: Ketamine can be Norkus et al., 1 c . Amantadine has been
administered by intravenous infusion g shown to improve activity in dogs with
kg/min) or by intermittent intravenous boluses osteoarthritis when combined with meloxicam
during anaesthesia . 1 mg kg . After a bolus (Lascelles et al., 8 , and it has been
it is quite common to see transient apnoea or a successfully used to treat neuropathic pain in a
change in respiratory pattern. Ketamine infusion dog (Madden et al., 14 . It is renally excreted.
has been shown to reduce inhalant anaesthetic Anecdotally, it has been reported that
requirements. amantadine can cause vomiting in dogs.
Postoperative analgesia: Ketamine can be Nitrous oxide
administered as a low-dose intravenous Nitrous oxide has long been used as an
infusion 1 g kg min to provide analgesia analgesic and anaesthetic-sparing agent in
in the postoperative period. Adverse e ects are humans and animals. It is an NMDA receptor
rarely seen at such low doses. agner et al. antagonist, and its intraoperative use has been
demonstrated that following forelimb shown to reduce post-surgical opioid
amputation, dogs receiving ketamine 1 g requirements and chronic pain in humans
kg min intraoperatively followed by g kg (Stiglitz et al., 1 ; Chan et al., 11 . It is a gas
min for 18 hours postoperatively had lower pain that can be mixed with oxygen during
scores at 1 and 18 hours post surgery anaesthesia, typically a 7 or
compared with dogs that did not receive oxygen:nitrous oxide mix. Use of an oxygen
ketamine. They were perceived by their owners analyser or a pulse oximeter is required when it
to be more active at home days after surgery. is used in a circle system due to the potential
Similar results have been reported in humans for delivery of low oxygen concentrations to
and there is evidence in humans that use of the patient. Nitrous oxide accumulates in
low-dose ketamine reduces postoperative gas lled cavities and is contraindicated in
opioid requirement after major surgery. There is patients with gastric dilatation and volvulus,
limited evidence regarding the optimal duration pneumothorax and similar conditions. It is
of ketamine infusion, but the authors usually also contraindicated for patients with
use it for at least 4 hours postoperatively. or intracranial disease. Nitrous oxide causes a
day patients it can be used intraoperatively, and reduction in DNA synthesis, temporary bone
postoperatively until the patient is discharged. marrow changes, and neurological symptoms.
Theatre pollution with nitrous oxide must be
Treatment of chronic pain: Although not avoided by use of proper scavenging; it
evidence-based, some anaesthetists should not be used during mask or
recommend using ketamine to ‘break the pain chamber inductions.

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