Effects Of Epidural Dexmedetomidine With0.25％Ropivacaine Hydrochloride On Analgesia And Sedation In Arthroscopic Knee Surgery Patients

Objective: Epidural anaesthesia with ropivacaine hydrochloride is themost common approach which is used for lower limb surgery, andpostoperative pain relief is an important issue with ropivacaine. But highconcentration of local anaesthetics have intense sensory and motor block andcan cause injury due to the greater cardio-vascular and central nervous systemtoxicity, which is very difficult to first aid. So it is a necessity to find the otherway to use epidural anaesthesia safely. Dexmedetomidine is a highly selectiveα2-adrenergic agonist which has been used for analgesia and sedation.and ithas an eight-fold greater affinity for a2-adrenergic receptors than clonidine.The analgesic action of intrathecal or epidural clonidine was demonstratedclinically. Yoshitomi et al[1]demonstrate that Dexmedetomidine enhances thelocal anesthetic action and decrease ED50of local anesthetic. Brummett et al[2]report the approach of combining ropivacaine with Dexmedetomidine did notdetect any neurotoxicity.The present study choose Dexmedetomidine(Dex) on the0.25％ropivacaine hydrochloride combined with epidural anesthesia, finding theoptimum concentration of Dexmedetomidine with local anesthetic andviewing the effect on local anaesthetics, such as hemodynamic, analgesia andsedative potentiating effects of epidurally administered Dexmedetomidinewhen combined with local anaesthetics in lower limbs surgeries.Methods：A total of eighty patients of both gender aged25-60years,American Society of Anaesthesiologist (ASA) physical status I and II whounderwent single arthroscopic knee surgery were enrolled into the presentstudy. Patients were randomly divided into four groups: D₁group(Dex0.125μg/kg), D₂group(Dex0.25μg/kg), D₃group(Dex0.5μg/kg), D₄ group(Dex1μg/kg), comprising20patients each, injection ropivacainehydrochloride at a time,20ml of0.25%, was administered epidurally(introduced at L_1-2 interspace, inserted3cm into the epidural space in adecurrent direction) in both the groups. On arrival in the operating room,patients were preloaded with Hydroxyethyl starch130/0.4Sodium ChlorideInjection at8-10ml/kg. All patients were monitored (PHILIPS IntelliVueMP50) with automated non-invasive blood pressure, pulse oximetry andelectrocardiogram. HR, MAP were recorded before anesthesia(T₀), afterepidural anesthesia10minutes(T₁), while incise the skin(T₂), into the articularcavity(T₃),after into the articular cavity15minutes (T₄) until the operationfinished(T₅). Intraoperative pain scores and sedation were recorded whileincise the skin(T₂), into the articular cavity(T₃),after into the articular cavity15minutes (T₄) until the operation finished(T₅). Besides cardio-respiratoryparameters, SPO2, various block characteristics were also observed whichincluded sensory analgesic level and motor blockade at the beginning and endof the operation. Postoperatively, time to first pain and rescue analgesic, sideeffects, such as nausea, vomiting and uroschesis. At the end of study, data wascompiled systematically and analyzed using SPSS13.0, Value of P<0.05isconsidered significant and P<0.01as highly significant.Results：There were no significant differences between the four groupswith regard to gender, age, height, weight, sensory analgesic level, amount ofbleeding and duration of surgery, as well as MAP and heart rate at beforeanesthesia(T₀).1MAP and heart rate decreased in every group at after epidural anesthesia10minutes(T₁), while incise the skin(T₂), into the articular cavity(T₃),after intothe articular cavity15minutes (T₄) until the operation finished(T₅) than atbefore anesthesia(T₀)(P<0.01), and decreased in every group at T₂-T₅than atT₁(P<0.01), MAP in D₂,D₃, D₄groups were lower than D₁at T₂-T₅, whilethere were no significant differences between the three groups of D₂,D₃andD₄. At T₁-T₅, heart rate in D₃were lower than D₁(P<0.05), and no differencesbetween other groups. 2At T₂, pain scores in D₂, D₃and D₄groups were lower than D₁. Pain scoresin D₃were lower than D₂at T₃-T₄, but there were no significant differencesbetween D₃and D₄.3Patients who needed fewer analgesic in D₃and D₄than other groups. Butthere were no differences among the groups in the incidence of beginning topain.4Ramsay scores were significantly higher in D₃-D₄than D₁-D₂at every timeand higher in D₄than D₃, Ramsay scores in D₁and D₂had no significantdifferences.5At the beginning and at the end of operation, motor blockade was fewer inD₄than D₁and D₃.6Intraoperative, SPO2of four patients in group D₄had decreased, but canreturn to normal by some means.7Postoperatively, side effects in every group had no differences, but that werelower in D₃than other groups.8No differences were were found among the groups in the incidence ofmovement and period in hospital.Conclusion:1Dexmedetomidine has effects on MAP and heart rate, but their have novariation with concentration of Dexmedetomidine.2When Dexmedetomidine below the dose of0.5μg/kg, antinociceptive andsedative effects have variation with concentration of Dexmedetomidine, butwhen the dose to0.5μg/kg, antinociceptive effects have no variation withconcentration of Dexmedetomidine.3There is a ceiling effect of Dexmedetomidine on sensory block.4The main finding in this study was that Dexmedetomidine added as adjunctto light concentration of ropivacaine hydrochloride in patients undergoingsingle arthroscopic knee surgery, also has the advantage of increasinganalgesia for epidural analgesia. Dexmedetomidine0.5μg/kg providescomparable stable hemodynamics and establishment of sensory anesthesia,prolonged postoperative analgesia, lower consumption of postoperative analgesic for epidural analgesia, and much better analgesia and sedation levels.Above all, Dexmedetomidine0.5μg/kg seems to be a better epidural adjuvantadd to ropivacaine hydrochloride in lower limbs surgeries.