After institutional ethical committee approval, ASAI-II 56 patients were divided as control and BIS groups. Anesthesia was induced by bolus remifentanil 1 μg/kg in both groups; propofol 2 mg/kg in was used in the control group while propofol was titrated to BIS 45- 65 values in the BIS group. Anesthesia was maintained by remifentanil and propofol infusions. Drug consumption, time to extubation and awareness were recorded.

Demographic parameters were similar between the groups. Consumption of propofol was lower, and time to extubation was shorter in the BIS group; there was no difference between awareness among groups.

BIS monitoring was helpful for propofol titration and decreased propofol consumption, but not enough to prevent reaction to noxious stimuli. Standard anesthesia titration considering hemodynamic parameters was enough for most ASA I-II patients for lumbar discectomies. BIS might be more helpful for patients who cannot show hemodynamic responses to noxious stimuli. More studies are needed to investigate the correlation between positioning and awareness using BIS monitoring. Keywords : Awareness, Bispectral index monitor, Propofol, Remifentanil, Lumbar discectomies