106
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
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α2-adrenoreceptor agonists should be considered as needed to provide
appropriate analgesia (Tranquilli et al. 2007, Hall et al. 2001, Gaynor et al.
2009).
Cardiovascular fitness level: Horses often have a higher resting vagal
(parasympathetic) tone compared to other species. Some horses that are fit
may have present with second-degree atrioventricular blocks that resolve
with minor exercise. These horses may have an increased sensitivity to the
cardiovascular effects of α2-adrenoreceptor agonists. Sometimes their heart
rates will reach as low as 18 beats per minute, which is a large cause of
concern! Thus combining α2-adrenoreceptor agonists with other agents to
lower the total dose of α2-adrenoreceptor agonists is strongly advised in
athletic horses.
Timing of procedure: Elective versus emergency. Some agents used during a
standing sedation protocol take up to 40 minutes (acetylpromazine) for onset
of action, thus not making them valuable agents to consider in an emergency.
In order to achieve adequate standing sedation the clinician should
understand the concept of onset of action. Some drugs take longer to achieve
maximum effect and if the horse is disturbed before achieving maximum
effect it may cause excitement and failure in achieving adequate sedation.
Length of procedure: Appropriate drug selection could decrease the dosing
interval and increase patient comfort during the procedure. This is best
achieved with administering drugs to maintain a “steady state” of the desired
level of sedation for the procedure. The longer the head hangs during
standing sedation the more pronounced the nasal oedema would be. This
may cause difficulty in maintaining normal ventilation, even in healthy horses.
Thus the clinician is strongly advised to find a method to keep the horses
head elevated during long procedures.
Equipment availability: Syringe drivers and infusion pumps may make the
administration of sedation cocktails more reliable as opposed to interval
boluses or infusion via gravity fed administration sets. Fancy equipment may
make the job easier and more “scientific”. However, high quality standing
sedation may be achieved with normal gravity administration sets.
Anticipated blood loss: Some agents are cautioned to use if you are expecting
rapid blood loss (acetylpromazine, α2-adrenoreceptor agonists). Thus their
judicious use is encouraged (Tranquilli et al. 2007, Hall et al. 2001).
Appropriate patient selection: Patients that are wild, anxious or known for
having a poor temperament are perhaps best operated on under general
anaesthesia as opposed to standing sedation. Excessively high doses may be
required to achieve standing sedation at the cost of compromising the
cardiovascular and respiratory system. This will help ensure safety of the
patient and personnel.
Pregnant mares: A general rule is to avoid unnecessary administration of any
drugs during pregnancy. Using the shortest acting agents may be of use to
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