Titration of Effect Site Concentration of Propofol for Conscious Sedation in Elderly Patients

Lee, Guie Yong

Abstract

BACKGROUND: Propofol is used for sedation during local and regional anesthesia. In order to evaluate the depth of sedation the bispectral index (BIS) and observer's sedation scoring (OAA/S) are widely used. However, there are few studies focused on elderly surgical patients during propofol-induced sedation for regional anesthesia. The goal of this study was to examine the effect site concentration of propofol for conscious sedation using the bispectral index (BIS) and hemodynamic changes in elderly patients.
METHODS
Sixteen patients aged 65 yrs or older presenting for elective surgery requiring regional anesthesia were studied. After performing spinal anesthesia, target plasma concentration of propofol was set at 2.5ng/ml. Effect site concentration was titrated by increasing and decreasing the target plasma concentration to maintain a BIS of 75 - 80. Effect site concentration, the OAA/S score, mean arterial pressure (MAP) and heart rate were measured for 1 hour every 5 minutes. Statistical analysis was performed using repeated measurement of ANOVA and correlation analysis.
RESULTS
The mean effect site concentrations was 1.3 +/- 0.2ng/ml and OAA/S score was 2.8 +/- 0.5 when the BIS was maintained between 75 - 80. The correlation coefficient for the effect site concentration versus the BIS was r = - 0.79. The MAP significantly decreased with an effect site concentration of propofol 1.0 and 1.2ng/ml and the heart rate significantly decreased at 1.2ng/ml. MAP decreased significantly at the level of conscious sedation.
CONCLUSIONS
The mean effect site concentration of propofol was 1.3 +/- 0.2ng/ml when the BIS was 75 - 80. There were significant correlation between the effect site concentration and BIS.