The analgesic effect of epidural clonidine after spinal surgery: a randomized placebo-controlled trial.

BACKGROUND Clonidine is an alpha(2) adrenoreceptor and imidazoline receptor agonist, which has analgesic, sedative, and minimum alveolar anesthetic concentration-sparing effects. It has been used orally, IV, and epidurally. In spinal surgery, there is a reluctance to use local anesthetic-based epidural analgesia postoperatively because of fears of masking important signs of nerve root or spinal cord injury. METHODS We randomized 66 patients undergoing uncomplicated decompressive spinal surgery to receive an epidural infusion of either clonidine (Group C) or saline placebo (Group P) postoperatively. Morphine consumption by patient-controlled analgesia device was recorded for 36 h. RESULTS Morphine consumption was significantly lower in Group C. The mean consumption at 36 h was 35 mg (95% confidence interval 21-50 mg) in Group C, compared with 61 mg (95% confidence interval 48-74 mg) in the control group. Nausea was significantly reduced in Group C (6.5%), when compared with placebo (38.2%). CONCLUSION Low-dose epidural clonidine significantly reduced the demand for morphine and reduced postoperative nausea with few side effects.