EPIDURAL CLONIDINE TREATMENT FOR REFRACTORY REFLEX SYMPATHETIC DYSTROPHY

Background: Intraspinally administered alpha2-adrenergic agonists may relieve pain in sympathetically maintained pain (SMP) syndromes, such as reflex sympathetic dystrophy (RSD), by spinal, peripheral, and cent ral nervous system actions. This study examined analgesic efficacy and side effects of epidurally administered clonidine in patients with se vere, refractory RSD. Methods: Twenty-six patients with severe chronic pain consistent with RSD were studied in a randomized, blinded, place bo-controlled design. Cervical or lumbar epidural catheters were inser ted for patients with upper or lower extremity RSD, respectively, and patients received, in random order on three consecutive days, epidural injection of clonidine, 300 or 700 mug, or placebo. Pain (by visual a nalog score (VAS) and McGill Pain Questionnaire), sedation, blood pres sure, and heart rate were monitored at specified intervals for 6 h aft er injection. Patients who responded to clonidine, but not placebo, th en entered a trial of open-label, continuous epidural infusion of clon idine (10-50 mug/h). Results: Clonidine, but not placebo, caused pain relief, sedation, and decreased blood pressure and heart rate after bo lus epidural injection. The smaller clonidine dose (300 mug), produced pain relief and decreases in blood pressure and heart rate similar to those of the 700 mug dose, but with less sedation. Epidural clonidine was infused for a mean of 43 days in 19 patients at a mean rate of 32 mug/h for sustained analgesia. Conclusions: Transdermal clonidine has been demonstrated to produce analgesia in the area surrounding its ap plication site in patients with SMP. The current study indicates that extensive analgesia may be obtained by epidural administration. Sedati on and hypotension may limit bolus epidural clonidine administration f or RSD. The role for chronic epidural infusion of clonidine has not ye t been established.