Transdermal clonidine: does it affect pain after abdominal hysterectomy?

Clonidine has analgesic properties. We evaluated the analgesic effect of clonidine perioperatively. Forty patients undergoing abdominal hysterectomy received randomly the evening before surgery transdermal clonidine covered with overlay (CLO group) or the overlay alone (CTL group). Ten min before induction they received i.v. clonidine 1 microgram.kg-1 (CLO) or normal saline (CTL). Induction was accomplished with fentanyl 5 micrograms.kg-1, thiopentone 5 mg.kg-1, cis-atracurium 0.15 mg.kg-1 and maintenance with sevoflurane 2% in 70% N2O. Hemodynamic parameters were recorded intraoperatively. Pain was assessed by VAS at rest and movement 2, 4, 6, 8, 24, 48, 72 h and 30 days, postoperatively. During the first 8 h postoperatively all patients received controlled analgesia with fentanyl followed by morphine i.m. 0.15 mg.kg-1 and paracetamol. From 24-72 h postoperatively, patients received 75 mg propoxyphene and 600 mg paracetamol i.m., on demand. Arterial blood pressure was lower in the CLO group 0, 3, 10 min after intubation. There was no difference in pain or fentanyl consumption 8 h postoperatively. The CLO group required less analgesics 24 h postoperatively (p = 0.023). The two groups did not differ in pain or analgesic requirements 72 h and 30 days postoperatively. Clonidine had a weak opioid sparing effect 24 h post-operatively, but did not affect pain in long term.