The Clinical Study On Target Controlled Infusion Of Propofol And Remifentanil In Elderly Patients

ObsjectiveThe elderly patients have been an important and special group with population aging in the world. However, there are not detailed information about a proper target concentration of propofol and remifentanil in the elderly patients in different age. We try to determine the effective plasma concentration of propofol(EC_P50) by TCI for loss of consciousness(LOC) in 50% of elderly patients aged 60～69yr and 70～79yr, and the effective plasma concentration of reminfentanil(EC_R50) by TCI combining propofol to prevent response to tracheal intubation(TI) and skin incision(SI) in 50% of elderly patients of that population, wish to provide some information for clinical anesthesia.MethodsWe recruited 151 ASAⅠ-Ⅲpatients aged 60～79yr, scheduled for elective surgery requiring tracheal intubation. They were divided into two groups according to their age: groupⅠ(60～69yr) and groupⅡ(70～79yr). In the first part of the study enrolling 40 patients, EC_P50 were determined with a modified Dixon's up-and-down method in two stages. The test space in the first stage was 0.5μg/ml,and the first patient in each group received an initial plasma concentration of propofol of 2.5μg/ml. After 3 or more negative-positive up-and-down crossovers, the initial test space was reduced to 0.2μg/ml. There were 6 or more negative-positive up-and-down crossovers in the second stage. EC_P50 were obtained by calculating the mean values for crossover midpoints in the second stage of each group. 111 patients in the second part of the study were divided into four groups according to receiving different stimuli (TI or SI):30 in groupⅠ-TI(TI of 60～69yr) , 30 in groupⅡ-TI(TI of 70～79yr), 26 in groupⅠ-SI(SI of 60～69yr) and 25 in groupⅡ-SI(SI of 70～79yr). Same to the first part, EC_R50 were determined with a modified Dixon's up-and-down method. The initial test space in the first stage was 0.5 ng/ml,and was reduced to 0.2 ng/ml in the second stage. The target plasma concentration of propofol was EC_P50 from the first part, and it might be adjusted with BIS value between 50 and 60. The first patient in group TI and all patients in group SI received an initial plasma concentration of reminfentanil of 3.5 ng/ml. After TI, the plasma concentration of reminfentanil in group SI was set at the designed concentration according to the up-and-down sequence, and the first patient in group SI received an plasma concentration of reminfentanil of 2.5 ng/ml. Then EC_R50 in groupⅠ-TI,Ⅱ-TI,Ⅰ-SI andⅡ-SI were calculated as the first part.ResultsTo patients aged 60～69yr, EC_P50 was 2.22μg/ml,and combining propofol with BIS value between 50 and 60,EC_R50 of group TI and group SI were 2.90ng/ml and 1.90ng/ml respectively. To patients aged 70～79yr, EC_P50 was 1.81μg/ml,decreasing compared with groupⅠ(P<0.05) , and EC_R50 of group TI and group SI were 3.16ng/ml and 1.77ng/ml respectively, similar to groupⅠ(P>0.05).ConclusionThe elderly patients in different age should be administered an accurate plasma concentration of propofol and remifentanil individually by TCI. To patients aged 60～79yr, EC_P50 descends with aging, and the plasma concentration of remifentanil combining propofol to prevent response to TI and SI could be adjusted according to status of individual patient, and influence on hemodynamics should be cautioned. Further studies are needed to seek proper concentration of propofol and remifentanil in patients of advanced age and with critical cardiovascular or pulmonary disease.