Intraoperative Clonidine in Spine Surgery: A Randomised Controlled Trial

Abstract

Patients undergoing spine surgery often experience post-operative pain. In this context, clonidine, an alpha-2 agonist, may be relevant due to its analgesic properties. We conducted a randomised, double-blinded, placebo-controlled trial to evaluate the effect of a single dose of intraoperative intravenous clonidine on post-operative opioid consumption, pain intensity and side effects. Patients undergoing spine surgery at Aarhus University Hospital, Denmark, were randomised to receive intraoperative clonidine (3 μg/kg) or placebo. The primary outcome was opioid consumption within the first 3 h after surgery. Secondary outcomes included opioid consumption within the first 6 h, pain intensity at rest and during coughing, post-operative nausea and vomiting (PONV), and sedation in the post-anaesthesia care unit (PACU). Additional outcomes included time to discharge from the PACU, length of hospital stay and daily opioid consumption after 1 month. Data from 120 patients (49 females, 71 males, mean age 65 ± 14 years) were available for analysis; 61 received clonidine and 59 received placebo. Post-operative intravenous morphine equivalents within 3 h were similar in the clonidine group 5 mg (0-15) and the placebo group 10 mg (0-15) (p = 0.58). Pain intensity at rest was 4 (0-5.5) in the clonidine group and 3 (0-5) in the placebo group upon arrival at the PACU (p = 0.20). No differences were observed between the clonidine and placebo groups regarding any secondary outcomes, except for hypotension, which was more frequent in the clonidine group (24 vs. 13 patients). A single dose of intraoperative clonidine did not reduce post-operative opioid consumption or pain intensity in patients undergoing spine surgery.

Keywords: intraoperative clonidine; postoperative pain; spine surgery.

FIGURE 1

Consort flow diagram. In total, 9 patients were excluded after randomisation. Of these, 7 were excluded before receiving the study drug: 5 due to bradycardia and/or hypotension following anaesthesia induction, as determined by the treating anaesthetist, and 2 due to surgery cancellation. An additional 2 patients were excluded after receiving the study drug due to surgical complications: 1 patient in the clonidine group experienced major bleeding during surgery and required admission to the intensive care unit (ICU), and 1 patient in the placebo group developed radicular pain and decreased strength, requiring an urgent MRI scan. For both patients, it was impossible to achieve any primary or secondary outcomes.

FIGURE 2

Pain intensity at rest and pain intensity during coughing. NRS, numeric rating scale. The median is represented by the bold horizontal line within the box. The box defines the interquartile range (IQR), with the upper and lower whiskers defining the minimum and maximum values, respectively.