46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
107
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minimise potential problems. If pregnant mares require standing sedation you
must administer an adequate volume of fluids (isotonic crystalloids) at 10 to
20 mL/kg/hr to help maintain placenta perfusion. Oxygen supplementation by
placing an endotracheal tube into the pharynx and administering oxygen at 10
to 15 L/min may help prevent hypoxemia (Tranquilli et al. 2007, Hall et al.
2001).
Male horses (geldings and stallions), in particular breeding stallions: Best to
avoid the phenothiazine derivatives (acetylpromazine) (Tranquilli et al. 2007,
Hall et al. 2001). Moderate to heavy sedation (with any agent) may also cause
paraphimosis and priapism. This needs to be managed when noticed.
Drugs used in various combinations
α2-adrenoreceptor agonists:
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Most reliable sedative agents in horses (Tranquilli et al. 2007, Hall et al.
2001).
Decreases cardiac output and causes an increase in vascular tone. Most
horses can handle the negative cardiovascular effects of this group of drugs.
Watch out for the athletic horses! May see an inappropriate bradycardia (sub
20 beats per minute).
Onset of action usually rapid: Xylazine < Detomidine << Romifidine (Ringer
et al. 2013, Rohrbach et al. 2009)
Duration of action dependent on dose and agent: Xylazine << Detomidine <
Romifidine (Rohrbach et al. 2009)
Level of ataxia is dependent on dose and agent: Xylazine > Detomidine >>
Romifidine (Ringer et al. 2013, Rohrbach et al. 2009)
Excellent analgesia in horses. However, analgesia is often NOT adequate for
surgical procedures! Therefore you must use in combination with
appropriate analgesics (local anaesthetics, NSAIDs and opioids)
Bolus administration is the typical method of administration. However,
constant rate infusion (spiked drip bag, syringe driver) is the most preferred
way of administering α2-adrenoreceptor agonists over a long period of time
(> 60 minutes). This avoids the seesaw effect (sedation too heavy – too light
– too heavy etc.).
Avoid, if possible in pregnant mares (decreases uterine perfusion) (Tranquilli
et al. 2007, Hall et al. 2001). Use at lowest possible dose and administer fluids
to try and improve uterine perfusion.
Keep the head raised, especially in long procedures. Helps to prevent nasal
congestion and oedema.
When used alone, ventilation is mostly preserved; provided muscle relaxation
does not cause upper airway obstruction (laryngeal paralysis, nasal congestion
and oedema from head down position).
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