Epidural clonidine enhances postoperative analgesia from a combined low-dose epidural bupivacaine and morphine regimen.

In a randomized, double-blind, placebo-controlled trial, the value of adding clonidine to a low-dose epidural regimen for postoperative pain treatment was assessed. Twenty-four patients scheduled for hysterectomy during combined thoracic epidural (bupivacaine and morphine) and general anesthesia were studied. Postoperative analgesia consisted of epidural bupivacaine (5 mg/h) and morphine (0.1 mg/h) for 12 h. In addition, the patients randomly received clonidine (75 micrograms), followed by an infusion of 18.75 micrograms/h or saline solution (placebo) epidurally. Pain was evaluated at rest, during cough, and during mobilization every hour. Sensory level of analgesia was evaluated by pinprick. We found no significant difference in pain scores at rest between the clonidine and placebo groups but an enhanced analgesic effect by clonidine during cough and mobilization (P less than 0.05). Arterial blood pressure decreased significantly during clonidine infusion and remained lower than in the control group throughout the study. We conclude that a continuous low-dose epidural clonidine infusion enhances analgesia from a combined low-dose epidural bupivacaine and morphine regimen after hysterectomy; however, the concomitant decrease in arterial blood pressure during epidural clonidine deserves further study before such a regimen can be recommended.