To minimize hemodynamic responses to laryngoscopy and endotracheal intubation, 10% lidocaine spray to laryngopharyngeal area seems to be favorable. The aim of this study was to evaluate plasma concentration and hemodynamic responses following different dose of 10% lidocaine spray before laryngoscopic intubation.

Fifteen patients (ASA I, II) were randomly allocated. Group I (n = 5) patients were received saline spray for control, group II (n = 5) patients were received 1 mg/kg 10% lidocaine spray on laryngopharynx before induction of anesthesia and received 1 mg/kg 10% lidocaine topical spray to trachea under direct laryngoscopic view one minute before intubation, group III (n = 5) patients were received 1.5 mg/kg lidocaine spray. Hemodynamic response were measured at baseline, postspray 1 min, postintubation, postspray 2, 4, 6, 8, 10 min. Arterial blood samples for lidocaine concentration analysis were obtained at baseline and 2, 4, 6, 8, 10, 20, 30, 60, 120 minutes after larygopharyngeal and intratracheal administration of lidocaine.

The highest lidocaine concentrations in arterial blood were 1.76 ± 0.52µgram/ml for group II, 2.86 ± 0.40µgram/ml for group III (mean ± SD) 2 to 10 minutes after laryngopharyngeal and intratracheal administration. There weren't any definitive toxic symptoms observed during the study. Hemodynamic responses of group II and III were not satisfactory but remarkably stable compared with group I. There were no differences between group II and III.

Sympathetic responses after 2-3 mg/kg lidocaine spray on laryngopharynx are favorably but not sufficiently attenuated during endotracheal intubation.