Biomedical Engineering Reference
In-Depth Information
advised. For procedures where a prolonged recovery is
anticipated “fruit smoothies” and dilute, noncitrus fruit
cordial can be offered via a large syringe, enabling
quantification of intake. If cerebral edema is a possible,
adverse effect of the procedure excessive fluid intake
should be prevented.
circumstances in which severe pain is present will result in
insufficient pain relief.
The dose of analgesic used, and the frequency and
duration of treatment, should be varied depending upon the
animal's response. Considerable variation will occur
between animals, so although the use of suggested dose
rates is a useful starting point, this will almost certainly
lead to over-dosage of some animals and provision of
inadequate analgesia for others. Development of reliable
methods of pain assessment would enable analgesic treat-
ment to be tailored to suit the needs of each individual
animal. Unfortunately, reliable techniques have yet to be
developed in nonhuman primates. At present, attempts
should be made to develop clinical scoring systems using
well-defined signs that all involved in the animal's care can
recognise. Repeated assessment, particularly after anal-
gesic administration, can help focus on those signs which
are most related to an individual's pain. Clearly, in different
circumstances, different signs will predominate
e
guarding
and splinting of the abdomen, vocalizations, reluctance to
move, altered posture, etc. Social housing of primates may
complicate the assessment of signs of pain because
submissive postures (often displayed when reintegrating
into the group) may be mistaken for pain behaviors. Brief,
temporary periods of separation from the group can be used
to help distinguish between these behaviors and it is helpful
to have someone familiar with the individuals normal
behavior involved in the assessment.
Reintroduction to Social Housing
Pair-housed or group-housed animals should be reintro-
duced to their social group as soon as possible in order to
avoid fighting upon reintroduction, but this must be
balanced carefully so that animals are not returned before
they can function normally and maintain their position in
the social hierarchy. Animals should be able to eat, drink,
ambulate well, and respond normally to stimulation before
reintroduction takes place; they should then be observed
(ideally remotely) for a period of time to ensure that
fighting does not occur. In the authors' experience the
optimum time for reintroduction is usually 6
e
24 hours
after the animal sits up postoperatively.
ANALGESIA
A goal of laboratory animal anesthesia is to enable the
animal model to return to normal as quickly as possible
following a procedure, and good analgesia is an essential
part of the process. Pre-emptive analgesia (given before the
onset of surgery) (see section “Adjunct drugs” above) can
form an important part of the anesthetic protocol. However,
it is important that good postoperative analgesia is also
provided, since postoperative pain can prolong the effects
of surgery and cause inappetence, in addition to being
a significant welfare concern. The analgesics available for
use in other animal species can be administered safely to
nonhuman primates, and suggested dose rates are given in
Table 17.7
. As well as procedural differences there is
considerable individual variation in the response to anal-
gesia, and so it is important that animals are observed
appropriately to enable adjustment of doses and frequen-
cies of administered analgesics.
Analgesic Techniques
When major surgery is undertaken, the opioid analgesic
buprenorphine should be given, either alone or preferably
in combination with a nonsteroidal antiinflammatory
(NSAID) such as carprofen or meloxicam, since this
combination may provide more effective pain relief by
acting at different parts of the pain system (for an excellent
summary of animal pain physiology, see
Livingston and
Chambers, 2000
). Infiltration of the surgical site with a long
acting local anesthetic can also be a useful adjunct to the
use of systemic analgesics. Nerve block techniques specific
to particular procedures (e.g. section “Neurosurgery”
above) may also be used. For a description of the use of
epidural morphine in nonhuman primates see
Popilskis,
et al., 2008
. Combining analgesic drugs and techniques in
this way is commonly referred to as “multimodal” pain
therapy. As well as providing more comprehensive anal-
gesic cover, the use of a multimodal analgesic technique
enables lower doses of individual agents to be used,
therefore reducing the possibility of side effects.
It is important to calculate the total dose of local
anesthetic administered to an animal, particularly for small
nonhuman primates, as many agents have a relatively
Pain Assessment
If attempts are to be made to alleviate pain, then it is vitally
important to try to assess how much pain is present, since
the choice of analgesic should be determined in some part
by the degree of pain that is present; inappropriate use of
potent analgesics may lead to the undesirable side-effects
of these agents outweighing any benefits arising from
alleviation of pain. For example, a high dose of a potent
opioid will reduce locomotor activity and food and water
intake. Similarly,
use
of
low potency
agents
in
