A dose reduction study of local anesthetic with addition of dexmedetomidine on postoperative epidural analgesia after total knee arthroplasty

Background
Epidural analgesia is still the preferred method of postoperative analgesia for total knee arthroplasty in many countries. Dexmedetomidine is a new alpha-2 agonist which had many beneficial effects when administered epidurally. The aim of study was to provide effective postoperative analgesia with hemodynamic stability through reduction of the amount of epidural local anesthetic by adding dexmedetomidine.
Methods
75 patients, 50–70 years old, ASA physical status I–III undergoing total knee arthroplasty were randomly divided into three equal groups, group I received 0.125% bupivacaine 5 ml/h for postoperative analgesia, group II received 4 ml of a mixture of bupivacaine 0.125% and dexmedetomidine 0.2 μg/kg/h and group III received 3 ml of a mixture of bupivacaine 0.125% and dexmedetomidine 0.2 μg/kg/h. Postoperative pain were scored by visual analog scale (VAS), sedation score, postoperative nalbuphine consumption and hemodynamic parameters were recorded every 4 h for 48 h postoperatively.
Results
The demographic data were comparable in all groups. VAS (visual analog scale) of pain showed a significant reduction between the two groups II, III and group I with insignificant difference between groups II and III at both rest and movement. The mean of nalbuphine consumption during the study period was significantly reduced in group II, III than in group I with insignificant difference between groups II and III. Sedation scores were significantly higher in groups II and III compared to group I. Heart rate was more reduced in groups II and III than in group I with insignificant difference between the groups. The mean arterial blood pressure was significantly reduced in group I than groups II and III from hour 8 till the end of the study.
Conclusion
Dexmedetomidine is an effective adjuvant to epidural bupivacaine for postoperative analgesia after total knee arthroplasty through reducing the amount of local anesthetic.