Comparison of C50 for Propofol-remifentanil Target-controlled Infusion and Bispectral Index at Loss of Consciousness and Response to Painful Stimulus in Elderly and Young Patients

摘要

Background:In this prospective randomized study,we compared the predicted blood and effect-site C50 for propofol and remifentanil target-controlled infusion (TCI) and the bispectral index (BIS) values at loss of consciousness (LOC) and response to a standard noxious painful stimulus (LOS) in elderly and young patients,respectively.We hypothesized that the elderly patients will require lower target concentration of both propofol and remifentanil at above two clinical end-points.Methods:There were 80 American Society of Anesthesiologists (ASA) physical status Ⅰ Ⅱ unpremedicated patients enrolled in this study,they were divided into elderly group (age ≥65 years,n =40) and young group (aged 18-54 years,n =40).Propofol was initially given to a predicted blood concentration of 1.2 μg/ml and thereafter increased by 0.3 μg/ml every 30 s until Observer's Assessment of Alertness and Sedation score was 1.The propofol level was kept constant,and remifentanil was given to provide a predict blood concentration of 2.0 ng/ml,and then increased by 0.3 ng/ml every 30 s until loss of response to a tetanic stimulus.BIS (version 3.22,BIS Quattro sensor) was also recorded.Results:In elderly group,the propofol effect-site C50 at LOC of was 1.5 (1.4-1.6) μg/ml,was significantly lower than that of young group,which was 2.2 (2.1-2.3) μg/ml,the remifentanil effect-site C50 at LOS was 3.5 (3.3-3.7) ng/ml in elderly patients,was similar with 3.7 (3.6-3.8) ng/ml in young patients.Fifty percent of patients lost consciousness at a BIS value of 57.3 (56.4-58.1),was similar with that of young group,which was 55.2 (54.0-56.3).Conclusion:In elderly patients,the predicted blood and effect-site concentrations of propofol at LOC were lower than that of young patients.At same sedation status,predicted blood and effect-site concentrations of remifentanil required at LOS were similar in elderly and young patients.BIS were not affected by age.Low-propofol/high-opioid may be optional TCI strategy for elderly patients.