Airway Protective Reflexes Evoked by Laryngeal Instillation of Distilled Water Under Sevoflurane General Anesthesia in Children

In Brief To investigate how sevoflurane modifies airway protective reflexes in anesthetized children, we recruited patients younger than 12-yr-old for our study. Anesthesia was induced with inhaled sevoflurane in oxygen. The airway was managed with a laryngeal mask airway and the patient breathing spontaneously. Depending on the depth of anesthesia, the subjects were divided into two groups: Group 1 and Group 2 (1% and 2% of end-tidal sevoflurane concentration, respectively). Behaviors of the larynx were assessed mainly by the fiberscopic images of the larynx as well as respiratory flow and esophageal pressure. A small dose, 0.02 mL/kg of distilled water (minimum 0.2 mL) was instilled to the larynx through a channel of the scope to evoke an airway protective reflex from the larynx. The responses were categorized into passive (laryngeal closure, laryngospasm, and apnea) and active (cough, expiration reflex, and swallowing reflex) responses. Ten subjects were included in each group. In both groups, the primary responses were passive; however, in Group 1, active reflexes were also observed in 8 of 10 subjects; no subjects in Group 2 had active reflexes (P < 0.01). We concluded that, in children, the depth of general anesthesia with sevoflurane modified airway protective reflexes. IMPLICATIONS: Some of the upper airway troubles during anesthesia are related to airway protective reflexes evoked from the larynx. Sevoflurane should modify these reflexes; however, systematic studies have never been performed in children. Fiberoptic visual observation was combined with conventional pressure measurements to evaluate detailed responses of the larynx in sevoflurane-anesthetized children.