The effect of two different administration methods of ropivacaine through femoral nerve catheter on postoperative pain relief

Objective To compare the effect of Ropivacaine by two different analgesic methods on pain relief after total knee replacement.Methods Forty patients for total knee replacement were randomly assigned to two groups,continuous group(group A,0.20% ropivacaine) and intermittent injection group (group B,0.33% ropivacaine).In group A,0.20% ropivacaine 5 ml/h was given through femoral nerve catheter,additional 5 ml (lock time 30 min) as patient controlled bolus.In group B,0.33% ropivacaine 20 ml was given through the catheter three times a day (q 8 h).All patients received intravenous fentanyl infusion for supplemental pain controll.Fentanyl was given as 10 μg/h and 20 μg by bolus if needed.VAS score in postoperative 48 h,sensation function of femoral nerve and Bromage score at 24 h after catheter removed were noted.Results On postoperation 24 h,VAS at rest or movement in group B is significantly lower than that in group A(P0.05 or P0.01).On postoperation 48 h,significant difference was detected between the two groups considering movement VAS(P0.05).Consumption of total ropivacaine in group B is lower than that in group A [(396±0) mg vs (562±47) mg,P0.01].Fentanyl consumption in group B were significantly lower than that in group A [(532±34) μg vs (557±44) μg,P0.05].No nerve function recovery delay was found in all patients.Conclusion The two analgesic methods both provide good postoperative pain control,little impact on nerve function.Analgesic comsumption was reduced by accepting 0.33% ropivacaine intermittently.