Postoperative analgesia with dexmedetomidine

Dexmedetomidine is an alpha-2-receptor agonist with sedative and analgesia-sparing properties. In a recent study, the analgesic efficacy of dexmedetomidine in the early postoperative period was compared with that of morphine. The results of the study showed that the use of dexmedetomidine significantly reduced the early postoperative need for morphine and was associated with a slower heart rate in the poatanaesthesia care unit.

The alpha-2-receptor agonist dexmedetomidine has for a long time been known to have sedative properties and analgesia-sparing properties, whilst not being associated with respiratory depression. For these reasons, a group from the Department of Anesthesiology in Wisconsin, hypothesized that dexmedetomidine might prove useful in the postoperative period for patients having major surgical procedures that are associated with significant pain.The aim of the study, which was published in the most recent edition of “Anesthesia & Analgesia,” was to compare the analgesic efficacy of dexmedetomidine with that of morphine in the early postoperative period.The study group was 34 patients scheduled for elective inpatient surgery. The patients were randomized equally to receive either dexmedetomidine or morphine sulfate 30minutes before the end of surgery. The two groups were similar for patient demographics, ASA physical status, surgical procedure, baseline haemodynamics, and intraoperative use of drugs and fluids.In the postanaesthesia care unit (PACU) and up to 24hours after surgery, sedation and analgesia assessments with a visual analog scale (VAS) were recorded every 5minutes for 20minutes and then every 15minutes thereafter. Escape analgesia was given if the VAS pain was >50.Heart rate (HR), mean arterial blood pressure (MABP) and respiratory rate (RR) were also determined in the PACU.The research findings show that the patients who had received dexmedetomidine for postoperative pain had significantly slower early postsurgical heart rate (by an average of 16bm). Compared with the control group receiving only morphine, the patients receiving dexmedetomidine required 66% less morphine in the PACU. At one hour into the recovery period, only 6 of the 17 dexmedetomidine-treated patients required additional analgesia with morphine, compared wtih 15 of the 17 patients in the control morphine-receiving group. The secondary outcomes that were measured in the PACU revealed similar MABP, respiratory rates, sedation and nausea scores, and times to discharge from PACU between the two treatment groups. The researchers suggest that these findings show that dexmedetomidine, when used as postoperative analgesia, has the “potential advantage of reducing myocardial work and consequently may prove beneficial to reduce ischaemic tendencies in the those patients with coronary artery disease.”(Source: Anesthesia & Analgesia 2004; Volume 98: Pages 153-8)