Research title : Objective asesssment of anesthetic depth under general anesthesia and conscious sedation using BIS monitor

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The Bispectral Index (BIS) monitor is used to assess anesthetic depth during anesthesia, and the present study investigated amnestic effects, estimated cerebral concentration of propofol (PPF), and BIS value following PPF administration by target control infusion.[Experiment 1] As a basic experiment, the relationship between the BIS value during PPF administration and estimated cerebral concentration of PPF was investigated, which revealed that a correlation existed between the BIS value and estimated cerebral concentration. However, the assessment of consciousness and amenesia levels based on the BIS value proved impossible.[Experiment 2] The amnestic effects of PPF during sedation induction and awakening were investigated. During the induction, amnestic effects were obtained at an estimated cerebral concentration of 0.91±0.21μg/ml, and during awakening, amnestic effects were obtained at an estimated cerebral concentration of 0.65±0.18μg/ml. Therefore, when under sedation, amnestic ef … More fects could be maintained at a lower concentration of PPF when compared to induction.[Experiment 3] During awakening following PPF administration, the effects of awakening stimulation on BIS value and post-sedation amnestic effects were investigated. The results showed that there was a rapid increase in BIS value if awakening stimulation was actively delivered after PPF administration. When awakening stimulation was delivered, although the estimated cerebral concentration of PPF was high, amnestic effects were lost and memory was regained. However, the BIS value required for memory recovery ranged widely, and no consistent tendencies were observed.[Experiment 4] In patients who were scheduled to undergo general anesthesia, in order to ascertain the effects of pre-medication on preoperative BIS value and memory, BIS value and amnestic effects were assessed upon the patient's entry in the operating room. The results showed significant differences in BIS value and amnestic effects among the different types of pre-medication. This suggests that the BIS monitor is also useful in assessing pre-medication. Less