[Clinical efficacy and pharmacokinetics of different concentrations of ropivacaine with the same dosage on blocking lumbar plexus with sciatic nerves].
OBJECTIVE
To test the clinical efficacy and pharmacokinetics of different concentrations of ropivacaine with the same dosage on blocking lumbar plexus with sciatic nerves.


METHODS
Written 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.


RESULTS
The 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.


CONCLUSIONS
With 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.
Xu
Hong-wei
HW
Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China.
Zhang
Lan
L
Cao
Wei
W
Zhang
Xiang
X
Zhang
Wen-sheng
WS
D000328:Adult; D000368:Aged; D000577:Amides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008160:Lumbosacral Plexus / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D000077212:Ropivacaine; D012584:Sciatic Nerve / Q000187:drug effects; D055815:Young Adult
D000577:Amides; D000077212:Ropivacaine