Respiratory Reflex Responses of the Larynx Differ between Sevoflurane and Propofol in Pediatric Patients

Abstract

Background The effects of anesthetics on airway protective reflexes have not been extensively characterized in children. The aim of this study was to compare the laryngeal reflex responses in children anesthetized with either sevoflurane or propofol under two levels of hypnosis using the Bispectral Index score (BIS). The authors hypothesized that the incidence of apnea with laryngospasm evoked by laryngeal stimulation would not differ between sevoflurane and propofol when used in equipotent doses and that laryngeal responsiveness would be diminished with increased levels of hypnosis. Methods Seventy children, aged 2-6 yr, scheduled to undergo elective surgery were randomly allocated to undergo propofol or sevoflurane anesthesia while breathing spontaneously through a laryngeal mask airway. Anesthesia was titrated to achieve the assigned level of hypnosis (BIS 40 +/- 5 or BIS 60 +/- 5) in random order. Laryngeal and respiratory responses were elicited by spraying distilled water on the laryngeal mucosa, and a blinded reviewer assessed evoked responses. Results Apnea with laryngospasm occurred more often during anesthesia with sevoflurane compared with propofol independent of the level of hypnosis: episodes lasting longer than 5 s, 34% versus 19% at BIS 40 and 34% versus 16% at BIS 60; episodes lasting longer than 10 s, 26% versus 10% at BIS 40 and 26% versus 6% at BIS 60 (group differences P < 0.04 and P < 0.01, respectively). In contrast, cough and expiration reflex occurred significantly more frequently in children anesthetized with propofol. Conclusion Laryngeal and respiratory reflex responses in children aged 2-6 yr were different between sevoflurane and propofol independent of the levels of hypnosis examined in this study.