The effect of cerebral monitoring on depth of anesthesia using auditory-evoked potential

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Monitoring depth of anesthesia may improve anesthetic dosing and postanesthetic recovery. The auditory-evoked potential (AEP) monitors provide an electroencephalogram-derived index, A-line autoregression index (AAI), that has been reported to correlate with central nervous system depressant effects of anesthetic drugs.

Patients and methods

Forty consenting female patients undergoing elective gynecological laparoscopic surgery procedures were assigned randomly to either a control group (standard clinical practice) or an AEP-monitored group. Although the AEP monitor was connected to all patients of both groups, in the control group, the inspired sevoflurane concentration was varied on the basis of standard clinical parameters (target=baseline hemodynamic parameters±15%). In the AEP-monitored group, the inspired sevoflurane concentration was titrated to maintain AAI (target=20±5).

Patients and methods

Heart rate, arterial blood pressure, inspiratory and expiratory gas concentration, and AAI were recorded in all patients of both groups, but AAI was made available only to the anesthesiologist assigned to AAI-monitored patients. The recovery times to achieve a white fast-track score greater than 12, an Aldrete score of 10, and the actual duration of postanesthesia care unit stay were determined.


The AAI-monitored group showed a reduction in the consumption of sevoflurane by 27% (18±5 vs. 13±4 ml/h, P=0.001) compared with the standard clinical parameters group (control) and also a highly significant reduction of end-tidal concentration of sevoflurane by 24% (2.5±0.3 vs. 1.9±0.5, P=0.000), but there was no significant difference between the two groups in the total doses of propofol, fentanyl, and cisatracurium. The average intraoperative AAI value in the AEP-monitored group was significantly higher than the control group (23.64±0.50 vs. 18.27±1.27, P=0.000).


The AAI-monitored group more rapidly achieved an Aldrete score of more than 9 (min) (32±8 vs. 40±7 min, P=0.028) and achieved fast-track eligibility of more than 12 (min) (28±10 vs. 45±12 min, P=0.002) compared with the control group. The duration of stay in the recovery room (72±28 vs. 102±48 min, P=0.02) was also significantly reduced in the AAI-monitored group.


The use of AEP monitoring as an adjunct to standard clinical monitors improved titration of anesthetic drugs therapy, facilitating early recovery.

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