Journal: Eur J Anaesthesiol 25(11):869-875, 2008. 38 References
Reprint: Department of Anesthesiology, Tohoku University Hospital, 1-1 Seiryomachi, Aoba-ku, Sendai 980-8574, Japan (E Masaki, MD)
Faculty Disclosure: Abstracted by J. Joyce, who has nothing to disclose.
Dexmedetomidine, a specific α2-receptor agonist, has both sedative and analgesic-sparing properties. While significant antinociceptive effects of systemic and intrathecal administration of dexmedetomidine have been demonstrated in animal models, studies examining the analgesic effects of systemic administration of dexmedetomidine at doses causing sedation in human volunteers and postoperative patients report conflicting results.
The primary end-point of this study was to determine whether the intraoperative systemic administration of dexmedetomidine at doses causing sedation improves the postoperative pain status of patients undergoing lower abdominal surgery for gynecological disease. The authors also investigated whether co-administration of intraoperative systemic dexmedetomidine and epidural neostigmine results in postoperative analgesic effects without producing undesirable intraoperative events. The combination of both adjuvants may be useful for a decrease in postoperative opioid demand and a diminished need for epidural block, which contribute to a quicker postoperative normalization of patient abilities with as few associated side-effects as possible.
The main findings of this study are that intraoperative systemic dexmedetomidine did not change postoperative pain score, although co-administration of systemic dexmedetomidine and epidural neostigmine resulted in analgesic effects in late postoperative periods without producing undesirable perioperative events. These results suggest that the intraoperative systemic infusion of dexmedetomidine at doses causing sedation does not improve the postoperative pain of patients undergoing lower abdominal surgery under continuous epidural infusion with ropivacaine for postoperative pain control, but that the co-administration of both agents may be useful for postoperative pain control because of lack of serious side-effects such as respiratory depression and hemodynamic changes.
The anesthetic and analgesic-sparing effects of dexmedetomidine have been well documented in animal and human studies. In the present study, sevoflurane requirements to maintain the same BIS value were slightly and insignificantly reduced by dexmedetomidine. The intraoperative administration of dexmedetomidine resulting in changing concentrations of sevoflurane would not have had analgesic effects or would have minimally affected postoperative pain status, and thus did not improve the postoperative pain status. The co-administration of dexmedetomidine and epidural neostigmine produced analgesic effects in late postoperative periods. However, the clinical significance may be limited, because the postoperative analgesic effects were improved by the co-administration at only 24 and 72 hours, the period's diminished need for analgesics after surgery and the authors did not assess pain scores on movement.
Dexmedetomidine and neostigmine may interact with each other and have analgesic effects similar to those displayed by the co-administration of clonidine and neostigmine. It may be an additive or synergistic effect secondary to the different sites and mechanisms of action of dexmedetomidine and neostigmine. In the spinal cord, α2-receptor agonists produce antinociception by decreasing the release of glutamate from primary afferent nerve terminals, and by depressing the noxiously evoked activity of wide dynamic range neurons. |
