Page 53 - BSAVA Guide to Pain Management in Small Animal Practice

BSAVA Guide to Pain Management in Small Animal Practice

VetBooks.ir procedure, for example, if the initial opioid has Postoperative analgesia and
worn o , if there is intense surgical stimulation,
analgesia for hospitalized patients
or as part of a balanced anaesthesia technique
aiming to reduce inhalation agent requirements Opioids should be used as part of a
multimodal analgesia strategy. Ideally, pain
and mitigate the e ects of anaesthesia on the assessment should be an integral part of the
circulatory system. Opioids can be administered use of opioids. The aims of pain assessment
intramuscularly, as an intravenous bolus or as are to identify when an animal is in pain, to try
an intravenous infusion. Adverse e ects such as and quantify the pain, to assess the degree
apnoea, respiratory depression or bradycardia and duration of e ect of the analgesic agents
may occur (less likely if the drug is administered used, and to enable opioids to be used to
intramuscularly, but the onset of analgesia will e ect, i.e. to increase or decrease the dose or
be delayed). Ideally, the patient’s ventilation
should be monitored using capnography, and dosing interval as required for the patient, or to
intermittent positive-pressure ventilation (IPPV) give an additional dose (top-up) if the initial
may be required. Bradycardia may be treated dose is not ade uate. he onset, e ects and
using glycopyrronium 1 g kg or atropine duration of the drug may vary with dose and
4 g kg intravenously if the patient route of administration. The response of the
becomes hypotensive. individual animal to the opioid may vary due to
To ensure that the patient is comfortable di erences in sensitivity to the drug, duration
during the recovery period, it may be wise to of the drug e ect, occurrence of adverse
administer a long-acting opioid (e.g. methadone e ects, and the in uence of disease e.g.
or buprenorphine) prior to discontinuation of the hepatic or renal disease) on the action and
anaesthetic if the analgesia provided by the duration of the drug. In particular, cats can
pre-anaesthetic medication is likely to be demonstrate marked individual variation in the
waning. For example, the author [CJ] often e ect and duration of di erent opioids.
administers a second dose of methadone Intravenous infusions are useful for providing
intramuscularly 4 hours after the pre sustained analgesia without the need for
anaesthetic medication. repeated injections in the postoperative period.

Intravenous infusions
Intravenous infusions are useful for providing intra- and postoperative analgesia. Compared
with repeated intramuscular or intravenous doses of analgesics, they provide a relatively
constant plasma concentration of the analgesic drug, which should result in a stable plane of
analgesia. syringe driver or volumetric uid pump must e used to ensure accurate dosing.
nfusions can e easily titrated to effect, usually starting with an intravenous olus a similar
dose to that which will be infused per hour) to ensure adequate plasma levels are reached,
then beginning the infusion and increasing or decreasing the dose as required, according to
regular patient assessment. For example, a bolus of 0.1 mg/kg of morphine can be followed
by an intravenous infusion of 0.1 mg/kg/hour. Additional boluses may be given during the
infusion, for example, if a patient receiving 0.1 mg/kg/hour morphine seems painful, an
intravenous bolus of 0.1 mg/kg could be administered, and the infusion rate increased to
0.2 mg/kg/hour.
t has ecome common practice to mi several different analgesic drugs together in a ag
of uids and administer the mi ture intra- or postoperatively. Typical mi tures are morphine or
fentanyl mixed with lidocaine and ketamine (MLK or FLK, see table below). In the author’s [CJ]
opinion, it is preferable to administer the drugs separately, with the advantage that the

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