Target-controlled infusion with propofol for conscious sedation in patients undergoing epidural anesthesia

Objective To investigate the feasibility of target-con trolled infusion (TCI) with propofol for conscious sedation in patients undergoing epidural anesthesia and determine the required target blood concentration.Methods Fifty ASA I - II patients (27 male, 23 female) aged 20-60 years undergoing operation in lower abdomen or on lower extremity under epidural anesthesia were included in this study. The block height was lower than T,. Baseline BIS, SEF, HR, and MAP were measured before epidural anesthesia. Target blood propofol concentration was initially set at 0.5μg·ml-1 . The level of sedation was evaluated using OAA/S scale. New target blood concentration was set at least after 3 min, the delay between blood concentration and concentration at effect site, by increment of 0. 1μg·ml until OAA/ S score was reduced to 3. The target blood propofol concentration at different OAA/S scores was determined and also the correlation between OAA/S and BIS. TCI system consisted of (1) laptop P II (2) Graseby 3500 computerized infusion pump and (3) RS232 connector. Stelpump 1.06P( written by Johan Coetzee) was used for control program, and Marsh pharmacokinetic parameters were used in this study. Blood propofol concentration was measured by high-performance liquid chromatography (HF'LC) .Results The median prediction error (MDPE) was -23.1% . The median absolute prediction error (MDAPE) was 27.6% . The target blood propofol concentration for conscious sedation (OAA/S 3) was (1.74 ?.13)fig' ml1 . There was a good correlation between BIS and target blood concentration (r= -0.80,P0.05). Conclusions TCI with propofol for conscious sedation in patients undergoing epidural anesthesia has the advantages of good control, appropriate sedation and less hemodynamic effect and can be used clinically.