Pharmacokinetics of different concentration of ropivacaine following lumbar plexus combined with sciatic nerve block / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the pharmacokinetics of ropivacaine following lumbar plexus combined with sciatic nerve block for knee arthroscopy. Methods After obtaining written informed consent 16 ASAⅠorⅡpatients of both sexes (8 males ,8 females) scheduled for unilateral knee arthroscopy under lumbar plexus combined with sciatic nerve block with ropivacaine were randomly divided into 2 groups (n = 8 each) : group A received 0.5% ropivacaine 30 ml (15.0 mg) and group B received 0.75% ropivacaine 30 ml (22.5 mg) . Blood samples were taken from radial artery immediately after and at 5, 10, 15, 30, 45, 60, 120 and 180 min after drug administration for determination of plasma ropivacaine concentration by HPLC. The pharmacokinetic parameters were calculated using 3p97 computer program. Results The two groups were comparable with respect to sex ratio (M/F), age, body weight, height, duration of operation and amount of fluid infused. The main pharmacokinetic parameters in group A and B were: Cmax(1.4?0.3) mg?L-1 and (2.7?0.9) mg?L-1;AUC (3.88?0.28) mg?L-1?h-1 and (7.13?0.65) mg?L-1?h-1;t1/2?(0.44?0.19)h and (0.60?0.34)h; t1/2?(3.4?0.4)h and (2.4?0.5)h. The Cmax in group B was significantly higher than that in group A. The Cmax of ropivacaine reached 3.57 mg?L-1 in group B. No patient developed central nervous system or cardiac toxicity.Conclusion The plasma concentration versus time curve is fitted to two-compartment pharmacokinetic model. Lumbar plexus combined with sciatic nerve block with 0.5% ropivacaine 30 ml is safer.