INTRAVENOUS OR EPIDURAL CLONIDINE FOR INTRAOPERATIVE AND POSTOPERATIVE ANALGESIA

Background. Intravenous and epidural clonidine both produce postoperat ive analgesia. Several experimental reports demonstrate a spinal site of action for the analgesic effects of this alpha2-adrenoceptor agonis t. Therefore, the authors evaluated the clinical analgesic benefits of using clonidine, both intra- and postoperatively, by the epidural or the intravenous route. Methods: Using a randomized prospective double- blind study design, 40 patients, between 18 and 50 yr of age, undergoi ng intestinal surgery under general propofol/nitrous oxide anesthesia, were enrolled. Before anesthesia, an epidural catheter was inserted a t the L1-L2 interspace. At induction, a clonidine infusion was started at the doses of 4 mug/kg in 1 0 ml during 20 min, followed by 2 mug . kg-1 . h-1 (5 ml/h) during 12 h, either by the epidural (group 1) or by the intravenous (group 2) route. Intraoperatively, increased blood pressure and heart rate not responding to additional propofol bolus (0 .5 mg/kg) was treated with a bolus of alfentanil (7 mug/kg). Postopera tively, morphine boluses (1.5 mg) were given through a PCA device acco rding to the patient's need. Intraoperative analgesia was assessed by the alfentanil requirements. Postoperative analgesia was assessed by r ecording the morphine requirements, the visual analogue scale (VAS) at rest and after mobilization, and the patients' analgesia scale at 0, 3, 6, 12, 18, 24, and 36 postoperative hours. Sedation analogue scale and side effects were also recorded. Heart rate and blood pressure wer e particularly detailed during the first 2 h of the clonidine infusion . Plasma clonidine concentrations were measured after 20 min and 6, 12 , and 24 h. Results: Epidural clonidine significantly reduced the intr aoperative alfentanil requirements (0.93 +/- 1.2 in group 1 vs. 2.4 +/ - 1.8 mg in group 2). The postoperative morphine requirements were als o reduced during the first 6 h (8.3 +/- 5.8 in group 1 vs. 17.8 +/- 13 .4 mg in group 2). The VAS were comparable in both groups, despite the better patients' analgesia score reported in the epidural group durin g the first 12 h. There was no difference in sedation score at any tim e interval considered. Epidural and intravenous clonidine reduced hear t rate and blood pressure to the same extent. The plasma clonidine con centrations were less in the epidural group only after the loading dos es. Conclusions: Epidural clonidine reduces the intra- and early posto perative analgesic requirements when compared with the same dose given by the intravenous route. The side effects were similar with the two routes of administration.