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

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.

Evaluation of entropy for monitoring the depth of anesthesia ：ompared with bispectral index： a multicenter clinical trial

Background As a new electroencephalogram （EEG） signal processing technique for monitoring the depth of anesthesia, entropy consists of two indices： reaction entropy （RE） and state entropy （SE）. Our study compared entropy with classical bispectral index （BIS） in reduction of myoelectrical interference and noxious stimuli with EEG signals. Methods Two hundred and eighty patients （ASA I-II, 18-60 years old） undergoing scheduled surgeries from seven medical centers were enrolled. Anesthesia induction was managed with propofol via the target-controlled infusion （TCI） system. The results of BIS, RE, SE, mean arterial pressure （MAP） and heart rate （HR） were recorded before anesthesia induction, at the moment of unconsciousness, before and 2 minutes after administration of muscle relaxant, and before and one and three minutes after the tracheal intubation. Results The values of half maximum effective concentrations （EC50）, 5% effective concentrations （EC05） and 95% effective concentrations （EC95） of propofol effect-site concentration at the onset of unconsciousness were 1.2 （1.1-1.3 μg/ml）, 2.5 （2.4-2.5 μg/ml） and 3.7 （3.7-3.8 μg/ml）, while those of the predicted plasma propofol concentration were 2.8 （2.7-2.9 μg/ml）, 3.9 （3.8-3.9 μg/ml） and 4.9 （4.8-5.0μg/ml）, respectively. The values of BIS, SE and RE were 62, 59 and 63 when 50% of patients lost consciousness, and 79, 80, 85 and 42, 37, 44, respectively, when 5% and 95% of patients were unconscious. The values of BIS, RE and SE dropped two minutes after the injection of muscle relaxant, but there were no significant differences between RE and SE. MAP and HR increased visibly, which indicated a reaction to tracheal intubation; the values of BIS, RE and SE, however, did not display any significant changes. Conclusions This large-sample multicentric study confirmed the values of RE and SE as approximating BIS value, at the onset of unconsciousness during propofol TCI anesthesia. After elimination of myoelectrical activation, all values of RE, SE and BIS decreased significantly and the three indices were less sensitive to noxious stimuli than cardiovascular responses.

基于BJS和TCJ的闭环麻醉给药控制软件设计

在麻醉过程中有效和适当地控制病人的麻醉深度是非常复杂的。针对开环靶控输注存在的操作不便和麻醉过程的个体差异,研究开发闭环麻醉给药控制软件,从BIS监护仪获取病人的麻醉深度指标,利用药代动力学原理、PID控制器控制TCI泵药物输注,解决开环TCI静脉麻醉不易控制和人为因素影响多的缺点,实现更为平稳、简单的麻醉过程,对个体化合理用药具有指导意义。