Page 49 - BSAVA Guide to Pain Management in Small Animal Practice

BSAVA Guide to Pain Management in Small Animal Practice

VetBooks.ir Opioids for pregnancy, Caesarean section, lactating mothers and very
young animals
There is very little published in the veterinary literature on analgesia for these patient groups. In
humans and la oratory animals, chronic opioid use during pregnancy can have adverse effects
on the progeny. However, short-term opioid use during pregnancy is unlikely to be detrimental
to the fetuses and may be necessary on welfare grounds (Mathews, 2005).
Opioids given to the dam during parturition or as part of an analgesia strategy for Caesarean
section may result in sedation and respiratory depression in the newborns due to penetration
of the placental barrier by the drug. While some authors recommend the use of opioids as pre-
anaesthetic medication, it may be preferable to postpone the use of opioids in the dam until
after the birth of the young to optimize their viability, and to consider other means of providing
analgesia for the dam (e.g. local anaesthetic techniques). Use of buprenorphine preoperatively
for Caesarean section is listed as a contraindication on the datasheet. Most anaesthetists agree
that short-term use of an opioid to provide analgesia to the dam following Caesarean section
is acceptable.
Opioids are secreted in milk and their use is not recommended (according to most
datasheets) during lactation. However, is important to treat pain in a nursing mother otherwise
she may demonstrate aggressive or aversive ehaviour towards her offspring. t seems sensi le
to use drugs that are less likely to cross into the milk, for example, those with low lipid solubility
such as morphine. However, methadone has been used in lactating humans with no detrimental
effect on the a y. f opioids are used in lactating mothers, drug administration could e timed
to avoid nursing at the time of pea plasma concentration, and the dam and offspring should
e monitored for adverse effects. The epidural or intrathecal routes of administration might e
appropriate in some cases.
Most drugs are not safety tested on young animals (less than 6–8 weeks old) and therefore
the manufacturers recommend caution in their use in such patients. Young animals are likely to
e more sensitive to the sedative effect of opioids, and very young animals less than wee s
old may e slower to meta olize these drugs. Therefore, use of low doses given to effect is
recommended (see ‘Clinical use’).
The cost- ene t analysis of using opioids in these cases and the a ove circumstances
should be considered; the datasheet of the particular opioid formulation should be checked;
and informed written consent to use drugs off licence, or unlicensed drugs, should e o tained
from the owner.

heart rate is very low less than about beats may become more lightly anaesthetized,
per minute) and/or there is a suspicion of requiring additional anaesthetic administration,
reduced cardiac output (usually assessed by for example, increasing the vaporizer setting.
measuring blood pressure), then the bradycardia Some opioids cause histamine release,
can be treated using an anticholinergic drug which can lead to urticaria, but also sometimes
atropine 4 g kg i.v. or glycopyrronium vasodilation with or without hypotension and
1 g kg i.v. . If alpha agonists have also tachycardia. This is common following pethidine
been used then administration of atipamezole administration so it should not be administered
can be considered instead of using intravenously. Morphine can also cause
anticholinergic drugs. In this case, the patient histamine release.

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