The limitations of the monitoring anesthetic depth by bispectral index and auditory evoked potential index during propofol anesthesia

Objective: To analysis the limitations of the monitoring the depth of anesthesia by bispectral index(BIS) and auditory evoked potential index(AEPI) during Propofol anesthesia. Methods: Eight patients were studied under propofol anesthesia. BIS, AEPI, SAP,DAP,HR and propofol concentration were recorded during induction operation and recovery period. The correlation among BIS, AEPI and propofol concentration were analyzed. Patients were surveyed about awareness during operation the next day . Results: During induction and recovery period AEPI was correlated fairly well with BIS and Propofol concentration and r was 0.57, -0.48 and 0.59, -0.40 respectively. During operation period,AEPI increased sharply and was not correlated with BIS and propofol concentration( r was 0.17, -0.01 respectively) but only 2 patients had clinical signs of light anesthesia; meanwhile BIS and propofol concentration were well correlated( r =-0.61) .All the patients were not recall and awareness during operation. Conclusion: For some patients, neither AEPI nor BIS values can completely parallel with the depth of anesthesia during operation period.