Estimating The Plasma-effect Site Equilibrium Rate Constant (K_e0) Of Propofol In Anesthesia Induction And Maintenance Stage

Objective:To estimate the plasma effect-site equilibrium rate constant (Keo) of propofol in anesthesia induction and maintenance phase, find out the differences in Keo between induction and maintenance phase, provide a reference for clinical application.Materials and Methods:29cases of elective surgery patients in ASA I or II were selected, no preoperative medication was used. Target concentration of effect site was4μg/ml in induction of anesthesia, and in maintenance phase when target control was stable and BIS was55-65,30mg and50mg propofol were separately used by intravenous injection. By recording the change of BIS in induction and maintenance phase of general anesthesia, according to the propofol pharmacokinetic model reported by Schnider and Marsh, calculate the propofol plasma-effect site equilibrium rate constants accordance with Minto proposed Tpeak.Results:Under Schnider’s pharmacokinetic model, Keo of anesthesia induction phase is0.62[0.38,1.19] min-1, Ke0of maintenance phase after a30mg dose is0.10[0.043,0.31] min-1, Keo of maintenance phase after a50mg dose is0.13[0.055,0.27] min-1. Analysis Keo of induction phase and maintenance phase (a small dose of30mg), P<0.01; analysis Ke0of induction phase and maintenance phase (a high dose of30mg), P<0.01; analysis Ke0of a small dose of30mg and Ke0that of a high dose of50mg in maintenance phase, P>0.05. Under Marsh’s pharmacokinetic model, Ke0of anesthesia induction phase is1.62[1.13,2.68]min-1, Ke0of maintenance phase after a30mg dose is0.43[0.21,0.97] min-1, Ke0of maintenance phase after a50mg dose is0.51[0.26,0.88] min-1. Analysis Ke0of induction phase and maintenance phase (a small dose of30mg), P<0.01; analysis Ke0of induction phase and maintenance phase (a high dose of30mg), P<0.01; analysis Ke0of a small dose of30mg and Ke0of a high dose of50mg in maintenance phase, P>0.05.Analysis Ke0in induction phase of Schnider and Marsh’s pharmacokinetic model, P<0.01; analysis Ke0in maintenance phase (a small dose of30mg) of Schnider and Marsh pharmacokinetic model, P<0.01; analysis Ke0in maintenance phase (a high dose of50mg) of Schnider and Marsh pharmacokinetic model, P<0.01.Conclusion:Both Schnider and Marsh’s pharmacokinetic model:there is significant difference between Ke0of anesthesia induction phase and that of maintenance phase (both30mg and50mg), there is no significant difference between the Ke0of30mgand50mg added bolus in maintenance phase. There is significant difference in Keo of induction phase,30mg and50mg added bolus in maintenance phase between Schnider pharmacokinetic model and that of Marsh pharmacokinetic model.