22
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Xylazine produces sedation at low doses with a dose of 1mg/kg-administered i/v
being suitable as premedication prior to induction with ketamine/propofol
combination. However it is short acting with effects only lasting 20 minutes in the
horse. Detomidine is very α2 receptor specific agonist. The recommended dose for
detomidine in donkeys is 10-20µg/kg. Joubert and colleagues demonstrated the dose
of 10µg/kg to be adequate in providing sedation but inadequate in providing sufficient
analgesia for moderately painful procedures. When used in donkeys the onset of
action is between 2-3 minutes when administered intravenously and the duration of
sedation lasting 20 minutes post administration.
Romifidine has been described for use in donkeys and causes dose dependant
sedation. The recommended dose of romifidine in horses ranges from 40-120 µg/kg.
However in the donkey the recommended dosage is 70 µg/kg with doses exceeding
100 µg/kg resulting in marked ataxia.
Opioids:
Butorphanol is a widely used opioid. The potency of the drug in horses is marked
and shows greater analgesia than morphine. The agonist-antagonist does aid in
sedation. When used in combination with detomidine at a dosage of 25 µg/kg and 10
µg/kg respectively, they cause adequate sedation and analgesia. The combination is
not without side effects. The combination does cause significant cardiovascular
depression, but more notably may affect a “chaney-stokes” breathing pattern. This
has not been described in horses sedated with this combination.
Induction and maintenance agents:
Barbiturates:
Thiopentone has been used successfully in donkeys. The dosage described is 7mg/kg
and sufficient when used in a donkey given premedication, of which the most
common combination was ACP at 0.03mg/kg and xylazine at 1mg/kg. The induction
phase is characterised by very quick onset of action (18 seconds) as with horses and
decrease in alveolar ventilation leading to increased respiratory rate. Maintenance of
anaesthesia with thiopentone is possible but delayed recovery is a common sequelae.
The maintenance infusion described is 8mg/kg thiopentone added to 500ml dextrose
5% solution. Pain control is poor with thiopentone and thus adequate analgesia must
be supplemented for any invasive procedures.
Cyclohexamines:
Ketamine is a commonly used induction agent in horses. Always used in combination
it has had success when used with α2 – agonists and benzodiazepines. The
metabolism of ketamine is much shorter in donkeys than horses. The use of
ketamine in combination with xylazine yields sufficient anaesthesia and analgesia for
short surgical procedures. The dosages of ketamine (2.0 mg/k g) and xylazine at
1mg/kg can be bolused repeatedly every 10 minutes. This is much shorter than the
25 minutes of anaesthesia described for horses. Ketamine and diazepam have been
used in combination to successfully induce a donkey given xylazine premed (1
mg/kg). The dosage sufficient to induce dissociative anaesthesia was 2.0 mg/kg and
0.1mg/kg of ketamine and diazepam respectively. The use of xylazine, ketamine and
guaifenesin as a triple drip works well for induction and maintenance of anaesthesia.
The combination of these commonly used drugs differs slightly when comparing the
triple drip in horses:
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