Laryngeal Reflex Study Under Propofol Anesthesia: Effect of Intravenous Lidocaine

Overview

To describe respiratory and laryngeal responses to laryngeal stimulation during propofol anesthesia in children. To determine whether the co-administration of lidocaine blunts these reflex responses. The outcome of primary interest is the reflex laryngospasm. Hypotheses: I: The severity of laryngospasm evoked by laryngeal stimulation is reduced 2 min. after iv. administration on 2mg/kg lidocaine in pediatric patients anesthetized with propofol (3mcg/ml). II:The incidence of laryngospasm elicited by controlled stimulation 10min. after iv. administration of lidocaine is equivalent to the response before the administration of lidocaine.

Based on our previous work assessing the laryngeal reflex responses in children, the use of propofol appears to be promising regarding a low incidence of laryngospasm. Compared with a sevoflurane-based anesthesia, the incidence was found to be significantly lower, but there is a high incidence of other reflex responses, such as coughing and expiration reflexes. The use of lidocaine has been advocated to reduce the incidence of laryngospasm in anesthetized children. However, based on clinical studies its effectiveness in the prevention or attenuation of laryngospasm is controversial. In a previous work using a established stimulation model (stimulating the laryngeal mucosa with a small amount of distilled water under direct fiberbronchoscopic observation), we observed a risk reduction of 60% of laryngospasm 2min. after the application of 2mg/kg bolus of lidocaine. This effect had already diminished after 10 min. The laryngeal reflex responses differ largely in children anesthetized with either inhalational anesthetics or with propofol. The impact iv administered lidocaine on laryngeal and respiratory reflex responses in children anesthetized with propofol has not been assessed, although this combination might result in a profound suppression of laryngeal reflex responses.