Performance of the rapidly extracted auditory evoked potentials index on detecting the recovery and loss of wakefulness in anesthetized and paralyzed patients

Purpose To assess the performance of the A-line~(TM) ARX-index(AAI) on detecting the recovery and loss of wakefulness in anesthetized and paralyzed patients. Methods Fourteen adult patients undergoing elective surgery,American Society of Anesthesiologists(ASA) physical status Ⅰ-Ⅱ,were anesthetized with propofol and vecuronium.Wakefulness was measured by the ability of the patient to respond to commands using the isolated forearm technique(IFT).After the patient responded,propofol was infused at 10 mg·kg~(-1)·h~(-1) until wakefulness was lost again.AAI was recorded continuously and analyzed off-line. Results The AAI showed a significant difference between the values registered 30 s before and 30 s after the recovery of wakefulness,and also between 30 s before and 30 s after the loss of wakefulness.The prediction probability(P_k) values for AAI were 0.786 and 0.864 during the transitions from unresponsiveness to wakefulness and from wakefulness to unresponsiveness.The area under the receiver operating characteristic(ROC) curve for the responsive and unresponsive values was 0.926(SE 0.002,95% CI 0.922-0.931),and the AAI values of 5%,50% and 95% predicted probability of wakefulness were 19(4.96%),29(50.25%) and 39(95.14%),respectively. Conclusions AAI may be a good predictor of recovery and loss of wakefulness for anesthetized and paralyzed patients.