Effects of Different Doses of Remifentanil Combined with Propofol on Anesthesia Induction

Objective To investigate the effects of the different doses of remifentanil combined with propofol on hemodynamics,the depth of anesthesia in patients during anesthesia induction and the appropriate dose of remifentanil.Methods 80 patients of ASA I~II,scheduled for elective surgery under general anesthesia,were randomly divided into 4 groups(n=20): fentanil group(Group F: 3～4 μg·kg-1) and remifentanil group(Group R).Group R were divided again into three groups based on the different doses of remifentanil(Group R1: remifentanil 0.1μg·kg-1·min-1,Group R2: remifentanil 0.2μg·kg-1·min-1and Group R3: remifentanil 0.4μg·kg-1·min-1).Anesthesia was induced with midazolam 0.05mg·kg-1,fentanyl or remifentanil,cis-atracurium 0.15 mg·kg-1,propofol 1 mg·kg-1 followed by continuous infusion 2mg·kg-1·h-1.Tracheal intubation and mechanically ventilation were performed 5 minutes later.Heart rate(HR),systolic blood pressure(SBP),diastolic blood pressure(DBP),mean arterial pressure(MAP),heart rate variability(HRV) and bispectral index(BIS) were recorded before induction of anesthesia(T0),just before intubation(T1),immediately(T2),at 3min,5min and 10min after tracheal intubation.At the same time,the adverse cardiovascular events including bradycardia,tachycardia,hypertension and hypotension and the time of losing consciousness were also recorded.Results ① HR and BP in each group were reduced significantly at T1 time point compared with those at T0,especially in group R3(P0.01).HR and BP in each group after tracheal intubation were increased.and they were higher than those at T0 time point(P0.05) in group F and group R1,but HR,BP at T4 and T5 in group R3 were less than those at T0(P0.01).② Compared with T0,HRV in group R1,R2 and F showed significantly at T1~T3(P0.05).There were no significant differences in group R2 at the different time points(P0.05).③ BIS in each group were reduced significantly after anesthesia induction(P0.01).BIS at T1~T4 in group R1 had significant differences compared with other groups(P0.05).④ The time of losing consciousness in group F were longer than those in group R(P0.01).There were no significant differences between group R1、R2、R3(P0.05).⑤ Tachycardia and hypertension in group R1and F after intubation Bradycardia and hypotension in group F and R3 were higher than those in group R1and R2(P0.05).Conclusion Remifentanil intravenously injected slowly(more than 60s) 1μg·kg-1 followed by iv infusion remifentanil 0.2μg·kg-1·min-1can get stable hemodynamics and satisfied depth of anesthesia.This dose of remifentanil is better dose for anesthesia induction when combined with propofol.