Does the addition of clonidine affect duration of analgesia of bupivacaine wound infiltration in inguinal hernia surgery?

We conducted a prospective, randomized, double-blind study to compare analgesia obtained by wound infiltration using 29 ml of 0.25% bupivacaine alone, or with the addition of clonidine hydrochloride 150 micrograms. A third group received bupivacaine wound infiltration with clonidine 150 micrograms i.m. to control for the systemic effects caused by absorption of clonidine. We studied 46 adults undergoing elective inguinal hernia repair. The general anaesthetic technique, postoperative analgesia and wound infiltration technique were standardized. There was no difference in time to first analgesic request or to total analgesic consumption between the three groups during the 24-h study. Visual analogue scores (VAS) at rest and after coughing were noted over a 24-h period. The only difference was higher VAS scores at rest at 24 h in the control group who received i.m. clonidine. We conclude that for elective inguinal hernia repair, postoperative analgesia obtained by bupivacaine wound infiltration was not improved by the addition of clonidine 150 micrograms.