Application Of A-line Auditory Evoked Potential Index In Propofol Target Controlled Infusion And Remifentanil Anesthesia In The Elderly

Objectives To evaluate the value of A-Line auditory evoked potential index (AAI) for monitoring the depth of anesthesia during general anesthesia with propofol target-controlled infusion (TCI) and remifentanil in the elderly,comparing with bispectral index (BIS). And to assess the interaction between remifentanil and propofol TCI according to AAI. Methods Sixty ASAâ… -â…¡grade or aged 65～77yr patients undergoing elective abdominal surgery were enrolled in this study. Anesthesia was induced with propofol administered by Diprifusor. The target concentration (Ct ) of Propofol was increased every 3 minute from 1mg·L^-1 step by step , with 0. 5 mg·L^-1 each step until OAA/ S sedation score became zero. Tracheal intubation was facilitated with rocurium and remifentanil. At every step, the ability to respond to verbal commamd and trapezius squeeze using the Oberserver's Assesment of Alertness/Sedation Scale (OAA/S), eyeflash reflex were recorded against AAI, BIS, hemodynamics, and effect site concentration of propofol (Ce). Parameters were recorded simultaneously during tracheal intubation too. After that, patients were randomly allocated to one of three groups (1.5 mg·L^-1,2.0 mg·L^-1,2.5mg·L^-1 propofol). Remifentanil infusion rates (IR) on inhibiting skin incision response was determined by sequential experimental method according to AAI<30. Keep AAI<30 by changing the remifentanil infusion rates throughout the operation. If can not, exclude the patient and next patient repeat the same experiment. Resultsâ‘ OAA/S, AAI, BIS and mean arterial pressure (MAP) decreased with the propofol Ce increasing;â‘¡There is positive correlation between AAI, BIS and OAA/S(r=0.917, 0.939), and negative correlation between propofol Ce and OAA/S(r=-0.936). AAI and BIS were negative correlated with propofol Ce (r=-0.906,-0.933);â‘¢MAP and HR decreased after remifentanil infusion, but AAI and BIS didn't changed. MAP and HR increased obviously and AAI increased only on the time of 1, 2 minute after intubation comparing with preintubation. But BIS still keep changless.â‘£The remifentanil IR50(CI) on inhibiting skin incision of three groups were 0.139μg·kg^-1·min^-1 (PRO2.5), 0.178μg·kg^-1·min^-1 (PRO2.0), 0.191μg·kg^-1·min^-1 (PRO1.5);⑤There was no difference between groups about the time of opening eyes, extubution, replying and corresponding AAI after operation. Numbers of patients using nicardipine and esmolol was PRO1.5> PRO2.0> PRO2.5. Conclusion AAI can reflect the depth of sedation and has a rapid response to noxious stimulate during propofol TCI and remifentanil anesthesia in elderly. Propofol 1.5².0 mg·L^-1 and remifentanil 0.15～0.2μg?kg^-1?min^-1 can keep enough sedation and analgesia in the elderly.