Epidural clonidine analgesia following surgery: Phase I

Abstract

Epidurally administered clonidine has been reported to produce postoperative analgesia. To assess the efficacy, safety, and appropriate dose of epidural clonidine for postoperative analgesia, clonidine (range, 100-900 μg in 100-μg increments) was injected in 22 patients following abdominal surgery or total knee arthroplasty (TKA). Clonidine produced analgesia, as measured by change in verbal pain scores and supplemental iv morphine usage. The largest doses examined (700-900 μg) produced complete pain relief for 5.0 ± 0.8 h (mean ± SEM; range 2-11 h), without other sensory or motor blockade. Clonidine also produced dose dependent decreases in blood pressure, being less following small (100-300 μg) and large (700-900 μg) doses than following intermediate (400-600 μg) doses. Six patients required iv ephedrine for treatment of blood pressure decrease of > 30%. Clonidine decreased heart rate 10-30% and produced transient sedation. Oxyhemoglobin saturation, serum glucose, and arterial blood gas tensions were not altered by clonidine, whereas there was a small (28%) dose-independent decrease in serum cortisol following clonidine injection. Clonidine was absorbed in a dose-dependent manner into the systemic circulation, with plasma concentrations 0.1-3.3 ng/ml 1 h following injection. These results suggest that hemodynamic depression and short-lasting analgesia may limit the usefulness of bolus epidural clonidine analgesia in the postoperative setting.