Effect Of Adding Dexmedetomidine To Ropivacaine For Pre-Emptive Fomeral Nerve Block On Different Concentration Of Ropivacaine For Postoperative Continuous Femoral Nerve Block Analgesia

Purpose:To observe the effect of adding dexmedetomidine to ropivacaine for pre-emptive fomeral nerve block on different concentration of ropivacaine for continuous femoral nerve block analgesia.Method:Sixty patients (ASA Ⅰ,Ⅱ) undergoing general anethesia for Total Knee Arthroplasty (TKA)were divided randomly into four equal groups,Group Dl(n=15),Rl(n=15),D2(n=15),R2(n=15).We do the pre-emptive fomeral nerve block with 0.5% ropivacaine 15mL+dexmedetomidine 0.5μg/kg for group D1 and group D2 While with pure 0.5% ropivacaine 15mL for group R1 and group R2.Then install a catheter which connected to the PCA pump after surgery.Evaluating the effect of femoral nerve block via acupuncture.Then starting the induction with propfol and remifetanyl TCI mode for each group.Insert a laryngeal mask under the effect of Cisatracurium.Anesth.esia maintenance was provieded from 2% sevoflurane.Patients given fentanyl O.lmg and tramadol 200mg half an hour before skin closure for fear of remifetanyl induced hyperpathia.Remove the laryngeal mask when patient awake after surgery and send the patient into postanesthesia unit(PACU).Connecting between femoral nerve catheter and PCA pump(contains 0.25% ropivacaine 150ml in group D1 and group R1 while the concentration was 0.2% in group D2 and group R2;parameter setting:3mL/h, bolus 8mL, lockout 60min)was implement by nurse in PACU.Patients receive tramadol 100mg orally when unbearable pain occur.Take a record of following parameters:2h,4h,8h,24h,48h resting VAS score and active VAS score after surgery;PCA pressing times within 48h after operation;the number of patients who need tramadol within 48h after operation;the time first use tramadol; dose of tramadol within postoperative 48 hours;side effects or complication such as local anesthesia toxicosis,nerve injury,hematoma,hypotension,bradycardia,nausea,vomit,myasthenia, falling.Result:There was no significant difference neither in the resting VAS score nor in the acting VAS score between group R1 and R2 at each time point(P> 0.05); The resting and active VAS scores of group Dl were significantly lower than group R1 at 8h and 24h(P<0.05), there was no significant difference at the rest time points(P>0.05); The resting and active VAS scores of group D1 were significantly lower than group D2 at 24h(P<0.05), there was no significant difference at the rest time points(P>0.05); There was no significant difference neither in the resting VAS score nor in the acting VAS score between group D2 and R2(P>0.05) at each time point.PCA pressing times within 48h after operation in group D1 was significantly lower than group R1; PCA pressing times within 48h after operation in group D2 was significantly lower than group R2.There was no difference among the 4 groups in the time first use tramadol, number of patients who need tramadol and dose of tramadol within postoperative 48 hours.There were no side effects or complications observed in all patients.Conclusion:Adding dexmedetomidine to ropivacaine for pre-emptive analgesia enhance the analgesic effect of postoperative continuous femoral block after total knee arthoplasty.