Objective To predict propofol-induced sedation by using bispectral analysis and to access
cardiorespiratory effects of the
different sedation levels of propofol by using OAA/S scores. Methods Twenty patients undergoing operations of low extremies under continuous epidural anesthesia were administered 70～150 mg intravenous propofol until the OAA/S scores decreased from 5 to 1. Recovery from sedation was observed until the OAA/S scores returned to 5. Bispectral index (BIS), spectral edge frequency (SEF) and
cardiorespiratory parameters were recorded according to different OAA/S scores during both the onset and recovery phases. Results The BIS and SEF exihibited significant correlation with OAA/S scores ( P <0.001). Heart rate, respiratory rate and blood pressure decreased when OAA/S score was lowered to 1. When OAA/S score reached most severe
depression was found and P ET CO 2 increased simultaneously. Conclusion Using BIS and SEF to predict the depth of propofol-induced sedation is reliable. When using propofol to induce sedation, we recommend a BIS value greater than 80 to achieve an OAA/S score of 3 or greater to avoid severe cardiorespiratory depression.