A clinical comparison of two anaesthetic protocols using lidocaine or medetomidine in horses

doi:10.1111/j.1467-2995.2006.00321.x

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Wiley InterScience

Veterinary Anaesthesia and Analgesia

Volume 34 Issue 4, Pages 257 - 268

Published Online: 12 Apr 2007

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RESEARCH PAPER

A clinical comparison of two anaesthetic protocols using lidocaine or medetomidine in horses

Simone K Ringer DVM, Karin Kalchofner DVM, Jolanda Boller DVM, Anton Fürst DVM, Diplomate ECVS & Regula Bettschart-Wolfensberger DVM, PhD, PD, Diplomate ECVA

Equine Hospital, VETSUISSE Faculty, University of Zürich, Zürich, Switzerland

Correspondence to Simone Ringer, Equine Hospital, VETSUISSE Faculty, University of Zürich, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland. E-mail: sringer@vetclinics.unizh.ch

KEYWORDS

anaesthesia • horse • lidocaine • medetomidine • recovery

Abstract

Objective To compare the effects of two balanced anaesthetic protocols on end-tidal isoflurane (Fe'ISO), cardiopulmonary performance and quality of recovery in horses.

Design Prospective blinded randomized clinical study.

Animals Sixty-nine client-owned horses, American Society of Anesthesiologists category I and II, undergoing elective surgery.

Methods The horses were premedicated with acepromazine (0.03 mg kg⁻¹) IM 30–60 minutes before induction of anaesthesia and were randomly assigned to one of two treatments: in group L (37 horses) xylazine (1 mg kg⁻¹) and in group M (31 horses) medetomidine (7 μg kg⁻¹) was administered IV for sedation. Anaesthesia was induced 5 minutes later with ketamine (2.2 mg kg⁻¹) and diazepam (0.02 mg kg⁻¹) IV and maintained with isoflurane in oxygen/air (initial FIO₂ 0.40–0.50) and a constant rate infusion (CRI) of either lidocaine (2 mg kg⁻¹/15 minutes loading dose followed by 50 μg kg⁻¹ minute⁻¹) (group L) or medetomidine (3.5 μg kg⁻¹ hour⁻¹) (group M). If horses showed movement or nystagmus, additional thiopental or ketamine was administered. Heart rate, mean arterial pressure (MAP), Fe'ISO and arterial blood gases were measured. Cardiac output was measured with the lithium dilution method in 10 (group L) and 11 (group M) horses every 45 minutes. Recovery was scored.

Results Heart rate and the cardiac index (CI) were significantly higher in group L with changes over time. In group M, MAP was significantly higher during the first 50 minutes. Group L needed more additional ketamine and thiopental to maintain a surgical plane of anaesthesia and Fe'ISO was significantly higher from 70 minutes. Recovery was longer in group M and of better quality. The significance level was set at p < 0.05.

Conclusions and clinical relevance In group M, maintenance of stable anaesthetic depth was easier and lower Fe'ISO was required to maintain a surgical plane of anaesthesia. Recoveries were longer but of better quality. The CI was higher in group L but cardiovascular function was generally well maintained in both groups.

Received 14 February 2006; accepted 11 August 2006.

DIGITAL OBJECT IDENTIFIER (DOI)

10.1111/j.1467-2995.2006.00321.x About DOI