Effects of volatile anesthetics on the activity of laryngeal 'drive' receptors in anesthetized dogs

Effects of halothane, isoflurane and sevoflurane on laryngeal drive recepto r activity were studied in the afferent activity of the superior laryngeal nerve in anesthetized spontaneously breathing dogs. Of 40 single units reco rded, most of them (65%) responded to the volatile anesthetics applied to t he isolated larynx at a concentration of 5%. The exposure to the anesthetic s resulted in either an inspiratory increase (15%), both inspiratory and ex piratory decrease (54%), or both inspiratory increase and expiratory decrea se (31%) responses. The average discharge frequency of the receptors tended to be decreased on inhalation of the anesthetics, where significant decrea ses were observed in both respiratory phases for halothane and at expiratio n for isoflurane, but in neither respiratory phase for sevoflurane. These r esults support an advantage of sevoflurane over halothane and isoflurane fo r induction of anesthesia to minimize the influence of the activity of lary ngeal drive receptors on the breathing pattern and airway stability.