The influence of initial target effect-site concentrations of propofol on the similarity of effect-sites concentrations at loss and return of consciousness in elderly female patients with the Diprifusor system

Abstract

Background: Whether effect-site concentrations of propofol (Cep) at loss of consciousness and return of consciousness (LOC and ROC, respectively) in elderly women using Diprifusor are similar is unclear. We investigated whether differences in initial target Cep (Ctarget) alter similarities between Cep values at LOC and ROC.

Materials and methods: In this study, female patients (n = 58, age = 72.5 ± 1.1 years) undergoing knee arthroplasty were administered propofol with Diprifusor. Cep at LOC and ROC were estimated for different Ctarget values (3.0-4.5 μg/ml). Pearson's correlation coefficient analysis and simple regression were performed to assess the relationship between Cep at LOC and ROC for each Ctarget. Differences in correlation coefficients of regression lines obtained from each Ctarget group were determined using the t-test.

Results: The different Ctarget groups did not show significant differences in total propofol levels and in Cep values at LOC or ROC. However, Cep at ROC was significantly higher than Cep at LOC when Ctarget was 4.0 and 4.5 μg/ml, whereas these Cep values were not significantly different in low Ctarget groups. Strong positive correlations were observed between Cep at LOC and ROC for all Ctarget groups. Regression coefficients for the different Ctarget groups were not significantly different. Compared to low (≤3.5 μg/ml) Ctarget groups, high Ctarget groups showed significantly shorter time until LOC. Induction quality was not significantly different among the groups.

Conclusions: In elderly women, Cep values at LOC are strong predictors of Cep at ROC when Ctarget is 3.0-4.5 μg/ml. High Ctarget groups (≥4.0 μg/ml) exhibited shorter induction times with normal cardiovascular stability.

Keywords: Diprifusor; elderly female; initial target concentration; loss and return of consciousness; propofol.

Figure 1

Linear regression between Cep values at ROC and LOC in each Ctarget group. Strong positive correlations were found between Cep values at LOC and Cep values at ROC in all Ctarget groups. The regression lines used ROC as an outcome variable (y) and LOC as a predictor variable (x)