title: The effects of isoflurane minimum alveolar concentration on withdrawal reflex activity evoked by repeated transcutaneous electrical stimulation in ponies.
abstract: The aim of this study was to quantify the effects of isoflurane at approximately the minimum alveolar concentration (peri-MAC) on the temporal summation (TS) of reflex activity in ponies. TS was evoked by repeated electrical stimulations applied at 5 Hz for 2 s on the digital nerve of the left forelimb of seven ponies. Surface electromyographic activity was recorded from the deltoid and common digital extensor muscles. TS thresholds and amplitude of response to stimulations of increasing intensities were assessed during anaesthesia at 0.85, 0.95 and 1.05 times the individual MAC, and after anaesthesia in standing animals. Under isoflurane anaesthesia, TS thresholds increased significantly in a concentration-dependent fashion and at each isoflurane MAC, the responses increased significantly for increasing stimulation intensities. A concentration-dependent depression of evoked reflexes with a reduction in the slopes of the stimulus-response function was observed for both muscles. The results demonstrated that with this model it is possible to describe and quantify the effects of anaesthetics on spinal sensory-motor processing in ponies.
authors.affiliation: Anaesthesiology Section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, Bern University, Bern, Switzerland. claudia.spadavecchia@kkh.unibe.ch
authors.forename: Claudia
authors.initials: C
authors.lastname: Spadavecchia
authors.forename: Olivier
authors.initials: O
authors.lastname: Levionnois
authors.forename: Peter
authors.initials: P
authors.lastname: Kronen
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
mesh_terms: D000769:Anesthesia, Inhalation / Q000662:veterinary; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004576:Electromyography / Q000662:veterinary; D006736:Horses / Q000502:physiology; D007530:Isoflurane / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D017288:Pain Threshold / Q000187:drug effects; D012018:Reflex / Q000187:drug effects*
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane