title: Effects of alfentanil on the equine electroencephalogram during anaesthesia with halothane in oxygen.
abstract: Opioids have variable effects on the minimum alveolar concentration of inhaled anaesthetics in the horse. During halothane anaesthesia at an end-tidal halothane concentration between 0.75 and 0.85 percent, the electroencephalogram (EEG) frequency power spectrum and the auditory evoked potential were recorded continuously in eight ponies during an infusion of approximately 40 micrograms kg-1 alfentanil over five minutes, and for a further 55 minutes. The spectral edge and median frequency of the EEG and the mid-latency of the auditory evoked potential at the time of maximum change of these variables were compared with those recorded before the start of the infusion. The mean (SD) spectral edge and median frequencies were reduced by 26 (5) percent and 36 (6) percent respectively. The mid-latency of the auditory evoked potential did not change. These cortical effects of alfentanil in the horse are qualitatively the same as in other species, suggesting that the alfentanil-induced excitement observed in horses in not of cortical origin.
authors.affiliation: Department of Veterinary Clinical Medicine, University of Cambridge.
authors.forename: C B
authors.initials: CB
authors.lastname: Johnson
authors.forename: P M
authors.initials: PM
authors.lastname: Taylor
mesh_terms: D015760:Alfentanil / Q000097:blood / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002490:Central Nervous System / Q000187:drug effects / Q000502:physiology; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology*; D003243:Consciousness / Q000187:drug effects / Q000502:physiology; D004338:Drug Combinations; D004569:Electroencephalography / Q000379:methods / Q000662:veterinary; D005072:Evoked Potentials, Auditory / Q000187:drug effects* / Q000502:physiology; D006221:Halothane / Q000008:administration & dosage / Q000494:pharmacology*; D006736:Horses / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007262:Infusions, Intravenous / Q000379:methods / Q000662:veterinary; D008297:Male; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D004338:Drug Combinations; D015760:Alfentanil; D010100:Oxygen; D006221:Halothane