Fig. 5. Relation of the effect site concentration and the Bispectral Index (BIS) at the time of syringe drop to the effect site ramp rate. With the wrong rate constant (  A ), it seemed that at higher ramp rates, more propofol was required at the effect site to induce syringe drop. However, when the individualized rate constant values were used, the effect site concentration associated with syringe drop was independent of the rate of increase of the effect site propofol concentration (  B ). This was consistent with the BIS results (  C ) showing that the BIS at the time of syringe drop seemed to be independent of the rate of increase of effect site propofol concentration.