24
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Pain assessment and management:
Equidae are categorised as prey species. The ability of the animal to not show
weakness is paramount to preventing becoming prey. With this in mind judging
algesia, the affects of an analgesic regimen are complicated and often unsuccessful.
Behavioural indicators have shown promise in a number of species as a means of
evaluating pain. Pain scoring is routinely performed in dog and cats to help quantify
the pain experienced and allow timeous intervention to optimize analgesic protocols
and minimize hospitalization periods. As of yet no formative pain scale exists in
donkeys. While general behavioural indicators of pain such as restlessness, anxiety
and lower head carriage have proven predictable signs in horses; none are reliably
seen in donkeys. This holds true for abdominal and limb associated pain. Response to
pain therapy is also ambiguous and unrewarding. The most important indicators in
donkeys are: failure to attend regular feedings and reluctance to move. Change in
demeanour such as dullness can be difficult to interpret and furthermore, quantify.
Thus analgesia peri-operatively should always be included and assumed even though
the clinical signs are vague and unpredictable.
Non-Steroidal Anti-inflammatory Drugs (NSAIDs):
Information specific to donkeys and NSAIDs use is limited. The pharmacokinetics of
phenylbutazone has been described. Phenylbutazone is used commonly to treated
pain associated with lameness or skeletal pathology. In horses the recommended
dosage for oral administration is 2.2mg/kg twice a day for up to 4 days before
reducing to once a day administration. The pharmacokinetics of phenylbutazone in
horses involves hepatic metabolism into mainly oxyphenbutazone.
The hepatic metabolism of phenylbutazone in donkeys is significantly higher than in
horses. Clearance times for phenylbutazone in donkeys can be as much as twice the
rate seen in horses. This correlates with the subsequent rapid accumulation of
oxyphenbutazone at twice the rate observed in horses.
The metabolite is thought to have been active but the pharmacokinetic profile in
donkeys has not been described. Thus based on the clearance and rate of metabolite
production it appears as if the phenylbutazone dose interval is half the period used in
horses. Flunixin meglumine (1.1mg/kg OID) also requires more frequent dosage
intervals with half the period between intervals required in h orses. Ketoprofen has
been described for use in horse and donkeys. In comparison the pharmacokinetics
suggest the elimination half-life of the drug is the same in both species. What is
significant is the volume of distribution in donkeys appears to be higher than in
horses. This has implications on dosage required for adequate effect. Thus it is
suggested the dosage interval is the same as in equines but a higher dose is required
than the 2.2mg/kg OID described in horses.
Monitoring Donkeys Intra-operatively:
All normal methods of monitoring equines should be practised with donkey
anaesthesia. Depth of anaesthesia is more difficult to ascertain when testing the
reflexes of the eye, namely palpebral reflexes and tearing associated with too light a
plane of anaesthesia, thus for accurate monitoring the anal reflex should be tested.
The breathing pattern in horses changes with lightening of anaesthetic. Horses tend
to increase their frequency as they begin to lighten. This does not hold true for the
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