Comparative Evaluation of Ropivacaine and Fentanyl Versus Ropivacaine and Fentanyl with Clonidine for Postoperative Epidural Analgesia in Total Knee Replacement Surgery.

Introduction: Clonidine an alpha 2 adrenoceptor agonist possesses analgesic properties and has been used as an adjuvant in epidural analgesia. The addition of clonidine to other analgesics may result in enhanced analgesia through additive mechanisms or synergistic mechanisms. The enhanced analgesia may lead to a decrease in the dosage of analgesic drugs along with reduction of side effects.

Aim: The purpose of this study was to evaluate the effect of adding clonidine to epidural ropivacaine and fentanyl mixture in terms of quality of analgesia and side effects in patients of total knee replacement surgery.

Materials and Methods: A prospective randomised double blind study was conducted on 60 patients of ASA physical status I, II and III who underwent unilateral total knee replacement surgery under combined spinal epidural anaesthesia. Patients were divided into two Groups A and B randomly. Postoperatively Group A received continuous epidural infusion of ropivacaine 2 mg.ml-1 and fentanyl 2 μg.ml-1 along with clonidine 2 μg.ml-1 in the range of 3-7 ml.hr-1 while Group B received the ropivacaine and fentanyl epidural solution. The postoperative VAS scores, haemodynamic parameters, motor block, sedation, nausea, vomiting and any other significant side effects were noted. The two groups were compared with student's t-test, Pearson's Chi square test and t-test using SPSS statistical software.

Results: Visual analog scale scores were lower in Group A (3.38) than in Group B (3.72). The average infusion rate was lower in Group A (4.7 ± 0.7 ml.hr-1 ) than in Group B (5.5 ± 0.7 ml.hr-1 ). Patients in Group A required less dosage of rescue pain medication Paracetamol (1g i.v.), diastolic pressure and heart rate were lower in Group A. The groups were comparable in terms of sedation, motor block and nausea vomiting.

Conclusion: Clonidine added to a ropivacaine and fentanyl mixture augmented the postoperative epidural analgesia without significant side effects.