Prediction Error of a Marsh’s Pharmacokinetic Parameter Set for Propofol TCI in Korean

Ho-Yeong Kil, M.D., Seung Joon Lee, M.D., Sang Ki Min, M.D.*

Department of Anesthesiology, Hallym University Hospital, Ajou University Hospital*, Seoul, South Korea

Background: Marsh`s pharmacokinetic parameter set is most widely used for target controlled infusion for propofol. However, Marsh`s model was derived from European population, and it is uncertain whether this model is adequate for oriental, especially korean.

Methods: Aftert IRB approval and ethical committee, informed consent was obtained from thirty ASA 1 adult patients who underwent minor orthopedic surgery. Atropine 0.5 mg was injected as premedication. ECG, pulse oximeter, radial artery cannulation for blood sampling and checking vital sign, IV line for drug infusion was prepared. All patients were received general anesthesia with propofol TCI(Mater TCI) supplemented by 67% N20 and 33% 02. Initial target of propofol was 6 mcg/ml and maintained around 4-6 mcg/ml according to bispectral index(40-50). In the middle of surgery, target concentration was increased to 6 mcg/ml and maintained until effect concentration was reached to same concentration. Three min after equilibration, blood sample was drawn from radial artery(3 ml) for estimation of concentration using HPLC. Target concentration was decreased gradually at the interval of 1 mcg/ml until end of surgery and blood sample was drawn as above mentioned method. Samples of 1-6 mcg/ml were compared with control sample value which was drawn before drug injection. Prediction error(%) was obtained from following formula: measured conc.-predicted conc./predicted conc.x100.

Results: Prediction errors at each concentration were as follows:

Target conc.(mcg/ml)	Measured Conc.(mcg/ml)	Prediction Error(%)
1	0.98+/-0.42	-2
2	1.85+/-0.56	-7.5
3	3.05+/-0.73	1.7
4	4.62+/-0.98	15.5
5	5.81+/-1.23	16.2
6	7.22+/-1.32	20.3

Conclusions: Prediction errors of propofol concentration derived from Marsh model were less than 25% in the concentration range of 1-6 mcg/ml, which was considered as usual concentration for clinical practice.