Objective. This study assesses the possibility that clonidine may decrease analgesic opioid demand in postoperative patients.

Methods. Twenty-five patients were allocated randomly after abdominal surgery to receive either an epidural bolus dose of fentanyl (1.0 mcg.kg⁻¹) followed by a 1.0 mcg.kg⁻¹h⁻¹ continuous epidural infusion, or an epidural bolus dose of fentanyl (1.0 mcg.kg⁻¹) followed by a continuous epidural infusion combining fentanyl 0.5 mcg.kg⁻¹.h⁻¹ and clonidine 0.3 mcg.kg⁻¹.h⁻¹. Pain was assessed at definite intervals on a visual analog scale (VAS) over 3 postoperative days. Epidural infusion was halved when VAS score was lower than 2. Patients were monitored with a pulse oxymeter over 12 hours during the first postoperative night. Plasma fentanyl was measured by radioimmunoassay when patients left the recovery room and at 8 a.m. on the first and the second postoperative days.

Results. VAS scores were comparable in the two groups of patients. The amount of fentanyl delivered was significantly lower in the fentanyl + clonidine group, as were the plasma fentanyl concentrations. The duration of SaO₂ < 90% episodes was significantly less prolonged in the fentanyl + clonidine group (3.5 ± 4.8 minutes versus 14.4 ± 14.6 minutes).

Conclusions. The combination of clonidine to epidural fentanyl allows a decrease in opioid requirements without impairing analgesia. Reduction of opioids administration may have beneficial effects on respiratory function in postoperative patients.