The accuracy of target-controlled infusion of propofol in Chinese / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the accuracy of target-controlled infusion (TCI) of propofol using pharmacokinetic parameters reported by Marsh to predict plasma propofol concentration in Chinese. MethodsTwenty-two ASA I - II patients were divided into two groups group Y aged65 yr ( n = 11). Patients with liver, kidney or cardiovascular diseases were excluded. The patients were premedicated with pethidine 50mg and phenobarhital 0.1 g im. Radial artery and internal jugular vein(IJV) were cannulated. The pharmacokinetic parameters incorporated in the Graseby 3500 pump we used were V1=228 ml-kg-1 , K10 =0.119 min-1 ,K12=0.112 min-1, K2l=0.055min-1 , K13 =0.0419 min-1 ,K31 =0.0033 min-1. Target concentration was started with 2ug-ml-1 and increased at increment of 1ugml-1 until loss of consciousness. The patient was then intubated. When target concentration of propofol was increased, the concentration of inhalation anesthetic was reduced to maintain hemodynamic stability. When target concentration of propofol was increased, arterial blood sample was taken 1-3 times for determination of plasma propofol concentration measured by HPLC (Agilent 1100) . Then blood samples every 10-15 min. For each sample prediction error(PE) and constancy error(CE) were calculated. For each patient median prediction error(MDPE), median absolute prediction error(MDAPE) . Median absolute constancy error (MDACE) and median constancy error (MDCE) were calculated.ResultsThere was remarkable initial overshot. PE and absolute PE were 63.3 % and 66.2 % in group E and 62.1 % and 62.7% in group Y. CE and absolute CE were -0.3% and 12.7% in group E and 0.6% and 13.5% in group Y. The median value of MDPE ( = the median value of MDAPE) was 78.1 % in group E and 66.1% in group Y. The median value of MDCE was 0.2% (group E) and 0.8% (group Y) and MDACE was 12.5% (group E) and 13.5% (group Y) . The measured concentrations were significantly linearly correlated with the premedicated concentrations. Conclusion TCI system with propofolpharmacokinetic parameters reported by Marsh can lead to initial overshot and underestimate the measured plasma propofol concentration but it can maintain a stable plasma concentration