• Hong-wei Xu, Lan Zhang, Wei Cao, Xiang Zhang, and Wen-sheng Zhang.
• Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China.
• Sichuan Da Xue Xue Bao Yi Xue Ban. 2009 May 1;40(3):495-8.

ObjectiveTo test the clinical efficacy and pharmacokinetics of different concentrations of ropivacaine with the same dosage on blocking lumbar plexus with sciatic nerves.MethodsWritten informed consents from 60 ASA I or II patients scheduled for unilateral lower-extremity surgery were obtained. The patients were randomly divided into two groups (n=30 each). Group A received 60 mL (lumbar-plexus 36 mL, sciatic nerve 24 mL) of 0.3% ropivacaine. Group B received 45 mL (lumbar-plexus 27 mL, sciatic nerve 18 mL) of 0.4% ropivacaine. Sensory and motor functions were evaluated at 2, 5, 10, 15, 20, 25, 30, and 35 minutes after drug injection. The duration of nerve blockade were recorded. Blood samples were randomly taken from 24 patients (12 for each group) for testing plasma ropivacine levels at 5, 15, 25, 35, 45, 60, 90, and 120 minutes after drug injection. The total plasma ropivacaine were determined by HPLC. The pharmacokinetic parameters were calculated using computer program DAS ver 2.0.ResultsThe onset time of nerve blockade in the two groups showed no difference. The length of blockade by ropivacaine in group A was shorter than in group B. The patients in group A had higher scores of sensory than the patients in group B. But group A had lower percentage of patients with > or = 2 Bromage scales than group B. The main pharmacokinetic parameters in group A and B were: Cmax (3.17 +/- 1.24) mg/L and (2.40 +/- 0.72) mg/L; tmax (25 +/- 12.3) min and (29 +/- 11.4) min, AUC(0-infinity) (248 +/- 45) mg/(L x min) and (215 +/- 56) mg/(L x min); t1/2alpha (25.5 +/- 9.5) min and (37.0 +/- 12.9) min; t1/2beta (208 +/- 89.0) min and (215 +/- 95.8) min, respectively.ConclusionWith the same dosage, ropivacaine, in a lower concentration achieves better insensate. The plasma concentration-time curve for ropivacaine fits into a two-compartment pharmacokinetic model. The larger volume of ropivacain produces greater Cmax, and AUC(0-infinity) than the lower volume of ropivacain with the same dosage.

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