• Yuan-Shiou Huang, Liu-Chi Lin, Billy K Huh, Michael J Sheen, Chun-Chang Yeh, Chih-Shung Wong, and Ching-Tang Wu.
• Department of Anesthesiology, Tri-Service General Hospital and National Defense Medical Center, Taipei, Taiwan, Republic of China.
• Anesth. Analg. 2007 May 1;104(5):1230-5, tables of contents.

BackgroundCombinations of epidural clonidine, local anesthetics, and opioids have improved postoperative analgesia after total knee arthroplasty. In this study we sought to determine the optimal epidural bolus dose of clonidine, which provides the best analgesia and fewest side effects.MethodsEighty ASA I-III patients, who underwent total knee arthroplasty were randomly assigned to one of four groups of 20 patients each. Identical epidural anesthesia procedures were used for all groups. After surgery, groups C0, C1, C2, and C4 received patient-controlled epidural analgesia (PCEA) with clonidine (0, 1.0, 2.0, or 4.0 mug/mL, respectively) and morphine (0.1 mg/mL) in 0.2% ropivacaine. The analgesia effect was estimated by PCEA consumption volume and visual analog pain scale at rest and with movement at 1, 2, 4, 12, 24, 48, and 72 h after surgery. Systolic blood pressure, heart rate, sedation, and sensory and motor blockade were also recorded for 72 h after surgery.ResultsThe PCEA consumption volume for groups C0, C1, C2, and C4 were 71.8 +/- 19.5 mL, 49.6 +/- 12.3 mL, 48.1 +/- 9.3 mL, and 39.4 +/- 9.0 mL, respectively. The clonidine groups experienced less postoperative pain (P = 0.002). In the C4 group, four patients had prolonged sensory blockade and one patient had both severe sedation and prolonged sensory motor blockade. No significant statistical difference in analgesic consumption (P = 0.78) and pain intensity (P = 0.66) between groups C1 and C2 were noted.ConclusionsThe optimal amount of epidural clonidine in a solution of morphine and ropivacaine for postoperative pain management is 1.0 microg/mL.

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