| OBJECTIVE The aim of this study was to compare a new auditory evoked potential index (ICO AEP index) and the bispectral index (BIS) to monitor the recovery and disappearance of wakefulness under the influence of muscle relaxants.MOTHODS Twenty-six ASA I-II patients,18-60yrs scheduled for elective surgery under general anesthesia were included in the study. For all patients in operation room (OR), bispectral index (BIS) was monitored by BISTM monitor of Convidien Company of American and new auditory evoked potential index (ICO Index) was monitored by AIRCRAFT Company of Spain. The isolated forearm technique was used as the indicator of wakefulness. The patient’s right arm was wrapped with soft surgical padding and a padded orthopedic tourniquet was placed over it. Patients received propofol via vein by Diprifusor TCI, the target concentration was set to4.0μg· mL-1. At the loss of eyelash reflex the orthopedic tourniquet was inflated to250mmHg and an intravenous rocuronium0.9mg· kg-1was administered. When the propofol effect-site concentration of3.0μg· mL-1was reached, the patient will be intubated and mechanical ventilated, the infusion of propofol would be stopped, and an experienced researcher would call the patient’s name and ask him to squeeze his hand in the patient’s right hand. When the patient responded immediately the propofol infusion was started again with a target concentration set to3.0μg· mL-1. The loss of consciousness was defined by the patient’s last response to the verbal command. The request for response was made until2min after the loss of response. Representative ICO and BIS values were compared using one way ANOVA with post hoc Tukey’stest. These values were as follows:ICO and BIS registered just before the induction, the minimum ICO and BIS (represented as the lowest value after induction for each patient), all ICO and BIS values during30s before and after the recovery of response, and during30s before and after the loss of response. All ICO and BIS values (per second) from2min after intubation to the time just before responding, and also the values from the time of loss of response to2min later were used as the unresponsive values. The responsive values were those recorded during the period from the recovery of response until the loss of response. All these responsive and unresponsive values were used to determine the receiver operating characteristic (ROC) curve, and the area under the ROC curve was calculated to summarize the discriminating power of ICO and BIS. Assessment of the non-linear association between ICO and BIS values (all the responsive and unresponsive values) and compared probability of wakefulness was accomplished with the binary logistic regression analysis.RESULTS The individual and mean (SD) ICO values at the following times:during the30s before recovery of wakefulness, during the30s after recovery of wakefulness, during the30s before loss of wakefulness, and during the30s after loss ofwakefulnesswere62.1±8.1、76.8±13.3,75.5±8.3.59.3±5.3, and the BIS values were67.6±3.4>74.2±3.9.73.6±3.3.65.2±4.0. There were of significant differences in ICO and BIS between the before and after of recovery and loss of wakefulness. The area under the receiver operating characteristic curve for the responsive and unresponsive values of ICO and BIS was0.921(95%CI0.918,0.925)、0.924(95%CI0.920,0.928), and no significant differences were between them. The ICO values of approximately5%、50%and95%predicted probability of wakefulness were54.2.66.8.79.4, and the BIS values were63.7、69.1、74.6. Logistic regression coefficient of ICO was significantly less than the BIS (0.234vs 0.540, P<0.001).CONCLUSION Both of ICO and BIS can be a good predictor of recovery and loss of wakefulness for anesthetized and paralyzed patients under muscle relaxation. ICO may be more valuable to monitor the wakefulness conversion. |
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