[Monitoring depth of anesthesia: a comparision between electroencephalographic nonlinear index and bispectral index].

Objective: To compare the efficiency and accuracy of electroencephalographic nonlinear index (ENI) and bispectral index (BIS) in monitoring depth of anesthesia during general anesthesia.

Methods: Thirty patients undergoing elective abdominal surgery were recruited. The ability of ENI and BIS to distinguish between the anesthetic states (awake, loss of eyelash reflex, loss of response, steady anesthesia, first reaction and extubation) was analyzed with prediction probability (Pk). Correlation between ENI and BIS was tested by nonparametric Spearman rank correlation analysis, with data paired from awake through to extubation. The clinical performances of ENI and BIS were evaluated with success rate, responsiveness, and recovery time.

Results: ENI and BIS were better than mean arterial pressure (MAP) and heart rate (HR) for distinguishing between the states of anesthesia. ENI correlated strongly with BIS from the stage of awake through to extubation (r = 0.93). No differences were found between ENI and BIS in success rate and responsiveness; but the recovery time was shorter with ENI than with BIS.

Conclusion: ENI and BIS provide similar information reflecting the states of anesthesia, which allows accurate distinguishment between different states of anesthesia. The clinical performance of ENI is better than that of BIS.