RESUMO
Objective To investigate the changes in auditory evoked potential index (AEPI) during endotracheal intubation and the effects of intravenous lidocaine or topical anesthesia of larynx and vocal cords with tetracaine on intubation response. Methods Thirty-six patients classified as ASA physical status and Mallampati intubation status I or II , aged 19-55 yr scheduled for elective surgery under general anesthesia were randomly divided into 3 groups with 12 patients in each group: (1) control group (C) ; (2) intravenous lidocaine group (L) and (3) topical tetracaine group (T). The patients were premedicated with intramuscular atropine 0.01 mg?kg-1 and phenobarbital 0.1 g. Anesthesia was induced with midazolam 30 ?g ? kg-1, fentanyl 3 ?g ? kg-1 and propofol 1.5-2.0 mg?kg-1 . Direct vision tracheal intubation was performed at 3 min after vecuronium 0.1 mg?kg-1 . In group L 1 % lidocaine 1 mg ? kg-1 was given i. v. after propofol injection. In group T the suproglottic area and vocal cords were sprayed with 1% tetracaine 3-5 ml before intubation. All intubations were performed by the same anesthesiologist. BP, HR, SpO2 and AAI value were recorded 1 min before and 1 min after intubation. The time between vecuronium injection and tracheal intubation was also recorded.Results AAI value, MAP and HR significantly increased after endotracheal intubation in all 3 groups. The increase in AAI value in group T was significantly larger than that in group C and L. The increase in MAP and HR in group L after intubation was significantly smaller in group L than in group C and T. There was no significant difference in MAP and HR between group C and T after intubation. Conclusion AAI is more sensitive than MAP and HR in terms of detecting the increase in AAI value induced by responses to tracheal intubation. Neither intravenous lidocaine nor tetracaine topical anesthesia of vocal cords inhibits the intubation. Intravenous lidocaine can attenuate the cardiovascular response to intubation.