• Enzo Vettorato, Gudrun Schöffmann, John G Burke, Alastair J N Gibson, and Eddie R Clutton.
• Royal (Dick) School of Veterinary Studies, Division of Veterinary Clinical Sciences, The University of Edinburgh, Easter Bush Veterinary Centre, Roslin, Midlothian, UK. ev2@dickwhitereferrals.com
• Vet Anaesth Analg. 2012 Sep 1;39(5):495-502.

ObjectiveTo compare isoflurane and sevoflurane in lambs undergoing prolonged anaesthesia for spinal surgery.Study DesignProspective randomised clinical study.AnimalsEighteen Scottish blackface lambs 3-6 weeks of age and weighing 10-17 kg.MethodsAfter intramuscular medetomidine, anaesthesia was induced and maintained with either isoflurane (group I) or sevoflurane (group S) delivered in oxygen. Meloxicam, morphine, a constant rate infusion of ketamine and atracurium were given intravenously (IV) during surgery. Lungs were ventilated to maintain normocapnia. with peak inspiratory pressures of 20-25 cmH(2) O. Ephedrine or dextran 40% was administered when mean arterial pressure (MAP) was <55 mmHg. Intrathecal morphine, and IV meloxicam and edrophonium were injected before recovery. Time to loss of palpebral reflex (TLPR) upon induction, cardiorespiratory variables, time at first swallowing and other movement, tracheal extubation, vocalisation, spontaneous head lifting (>1 minute), reunion with the ewe, and the number of MAP treatments were recorded. Statistical analysis utilised anova, Mann-Whitney, t-test or Pearson's correlation test as relevant. p < 0.05 was considered significant.ResultsEnd-tidal carbon dioxide (mean ± SD) was significantly lower in group S (5.5 ± 0.6 kPa) than in group I (5.8 ± 0.5 kPa) while MAP (70 ± 11 mmHg) and diastolic arterial blood pressure (60 ± 11 mmHg) were higher in group S than in group I (65 ± 12 and 54 ± 11 mmHg, respectively). No differences were found with TLPR and MAP treatments. Time (median, range) from end of anaesthesia to ewe-lamb reunion was briefer (p = 0.018) in group S (48, 20-63 minutes).ConclusionIsoflurane and sevoflurane are both suitable for maintaining general anaesthesia in lambs although sevoflurane, as used in this study, allows a more rapid reunion with the ewe.Clinical RelevanceThe principal advantage of sevoflurane over isoflurane during prolonged anaesthesia in lambs is a more rapid recovery.© 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

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