The Clinical Study Of Target-controlled Infusion Of Remifentanil,Propofol In Elderly Patients

ObjectiveWith the ageing of the population in our country,the elderly patients who need operation become more and more. The aim of this study was to compare effects of different target controlled plasma concentrations of remifentanil on the effective plasma concentration of propofol by TCI for loss of consciousness(LOC) in 50% of elderly patients aged 60-80yr,and to determine the effective plasma concentration of propofol by TCI combining remifentanil to prevent response to tracheal intubtion(TI) in 50% of elderly patients of that population. We try to find better combined for these two anesthetic agents in elderly patients,wish to provide some information for clinical anaesthesia.Methods105 ASAⅠ-Ⅱpatients, aged 60-80yr, scheduled for elective surgery requiring trachel intubation were recruited. In the first part of the study enrolling 90 patients,they were randomly divided into four groups according to target controlled plasma concentrations of remifentanil:GroupA(1ng/ml),GroupB(2ng/ml),GroupC(3ng/ml)andGroupD(4ng/ml).The EC50 of propofol 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 intial plasma concentration of propofol of 2.5μg /ml.After 3 or more negative-positive up-and-down crossovers,the intial test space was reduced to 0.2μg /ml. There were 6 or more negative-positive up-and-down crossovers in the second stage .The EC50 of propofol were obtained by calculating the mean values for crossover midpoints in the second stage of each group.There were 15 patients,aged 60-80yr, in the second part of the study.Same to the first part,EC50 of propofol were determined with a modified Dixon,s up-and-down method.The initial test space in the first stage was 0.5μg /ml,and was reduced to 0.2μg /ml in the second stage.The first patient in the second part received an initial plasma concentration of propofol of 2.5μg /ml.The plasma concentration of the next patient was set at the designed concentration according to the up-and-down sequence and the first patient..Then EC50 of propofol to prevent response to tracheal intubtion(TI) were calculated as the first part.ResultsIn the first part of the study,The EC50 of propofol was 2.50μg /ml in the groupA,2.24μg /ml in the groupB,2.16μg /ml in the groupC and 1.90μg /ml in the groupD.Comparing groupA,the EC50 of propofol was decreased significantly(P<0.05) in groupB,C,D.GroupD was decreased significantly(P<0.05)compared with groupB,C.In the second part of the study,to patients aged 60-80yr,EC50 of propofol by TCI combining remifentanil to prevent response to tracheal intubtion(TI) in 50% of elderly patients was 2.32μg /ml.ConclusionThe effects of different target controlled plasma concentrations of remifentanil on the EC50 of propofol were different in elderly patients.With the concentrations of remifentanil increased,the EC50 of propofol decreased in elderly patients. To patients 60-80yr,the plasma concentration of propofol combining remifentanil to prevent response to TI should 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.