• M Villalba, I Santiago, and I A Gomez de Segura.
• Animal Medicine and Surgery Department, Veterinary Faculty, University Complutense, Spain.
• Equine Vet. J. 2011 Nov 1;43(6):721-6.

Reasons For Performing StudyLidocaine and ketamine are administered to horses as a constant rate infusion (CRI) during inhalation anaesthesia to reduce anaesthetic requirements. Morphine decreases the minimum alveolar concentration (MAC) in some domestic animals; when administered as a CRI in horses, morphine does not promote haemodynamic and ventilatory changes and exerts a positive effect on recovery. Isoflurane-sparing effect of lidocaine, ketamine and morphine coadministration has been evaluated in small animals but not in horses.ObjectivesTo determine the reduction in isoflurane MAC produced by a CRI of lidocaine and ketamine, with or without morphine.HypothesisAddition of morphine to a lidocaine-ketamine infusion reduces isoflurane requirement and morphine does not impair the anaesthetic recovery of horses.MethodsSix healthy adult horses were anaesthetised 3 times with xylazine (1.1 mg/kg bwt i.v.), ketamine (3 mg/kg bwt i.v.) and isoflurane and received a CRI of lidocaine-ketamine (LK), morphine-lidocaine-ketamine (MLK) or saline (CTL). The loading doses of morphine and lidocaine were 0.15 mg/kg bwt i.v and 2 mg/kg bwt i.v. followed by a CRI at 0.1 mg/kg bwt/h and 3 mg/kg bwt/h, respectively. Ketamine was given as a CRI at 3 mg/kg bwt/h. Changes in MAC characterised the anaesthetic-sparing effect of the drug infusions under study and quality of recovery was assessed using a scoring system.ResultsMean isoflurane MAC (mean ± s.d.) in the CTL, LK and MLK groups was 1.25 ± 0.14%, 0.64 ± 0.20% and 0.59 ± 0.14%, respectively, with MAC reduction in the LK and MLK groups being 49 and 53% (P<0.001), respectively. No significant differences were observed between groups in recovery from anaesthesia.Conclusions And Clinical RelevanceAdministration of lidocaine and ketamine via CRI decreases isoflurane requirements. Coadministration of morphine does not provide further reduction in anaesthetic requirements and does not impair recovery.© 2011 EVJ Ltd.

39 keywords...

hide…