title: A clinical comparison of two anaesthetic protocols using lidocaine or medetomidine in horses.
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.
  
  
  METHODS
  Prospective blinded randomized clinical study.
  
  
  METHODS
  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 microg 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 microg kg(-1) minute(-1)) (group L) or medetomidine (3.5 microg 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
  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.
authors.affiliation: Equine Hospital, VETSUISSE Faculty, University of Zürich, Zürich, Switzerland. sringer@vetclinics.unizh.ch
authors.forename: Simone K
authors.initials: SK
authors.lastname: Ringer
authors.forename: Karin
authors.initials: K
authors.lastname: Kalchofner
authors.forename: Jolanda
authors.initials: J
authors.lastname: Boller
authors.forename: Anton
authors.initials: A
authors.lastname: Fürst
authors.forename: Regula
authors.initials: R
authors.lastname: Bettschart-Wolfensberger
mesh_terms: D000762:Anesthesia Recovery Period; D000768:Anesthesia, General / Q000662:veterinary; D000769:Anesthesia, Inhalation / Q000662:veterinary; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D005260:Female; D006736:Horses; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007530:Isoflurane / Q000494:pharmacology; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D006993:Hypnotics and Sedatives; D008012:Lidocaine; D007530:Isoflurane; D020926:Medetomidine