Dexmedetomidine is a selective alpha-2 adrenergic agonist. It is used to provide sedation and as an adjunct to a general anesthesia. BIS is sometimes considered an objective method to precisely determine how much propofol and remifentanil is needed during anesthesia. Since dexmedetomidine has both analgesic and “MAC sparing” properties, a closed-loop propofol / remifentanil drug delivery system might objectively demonstrate a decrease in the requirements of both in the presence of a dexmedetomidine infusion. Using such a system could also allow an objective assessment of the influence of a background dexmedetomidine infusion on hemodynamic responses, postoperative analgesia, and postoperative nausea and vomiting.
Dr. Marc Fischler and coauthors from the Department of Anesthesiology, Hôpital Foch, Suresnes, France, and coauthors randomized 66 patients scheduled for nonhemorrhagic elective surgery to receive dexmedetomidine or saline placebo as part of their closed-loop BIS-guided anesthesia delivery system administering a propofol and remifentanil anesthetic. The results of their investigation are published in this month’s issue of Anesthesia & Analgesia in the article “Dexmedetomidine Reduces Propofol and Remifentanil Requirements During Bispectral Index-Guided Closed-Loop Anesthesia: A Double-Blind, Placebo-Controlled Trial.”
Patients in the dexmedetomidine group received a bolus of 1 μg/kg administered over 10 minutes followed by a continuous infusion of 0.5 μg·kg-1·h-1 until skin closure. Patients were given morphine 0.1 mg/kg and paracetamol 1 g IV 45 minutes before the anticipated end of surgery. The patients who received dexmedetomidine were asleep about 1 minute faster, needed 23% less propofol and 25% less remifentanil during induction, 29% less propofol yet comparable amounts of remifentanil during anesthesia maintenance. Following surgery patients in the dexmedetomidine typically asked for morphine 4 hours after their procedure, compared to 1 hour for patients in the placebo group, suggesting sustained analgesia following an intraoperative dexmedetomidine infusion. Intraoperative ephedrine use, postoperative shivering, pruritus, and nausea and vomiting were similar between groups. No patient had intraoperative recall.
The results are not unexpected. The advantage of this study is that the closed-loop system is not influenced by clinician biases or preferences
Dexmedetomidine is a useful addition to a propofol/remifentanil anesthetic combination and can help supplement analgesia postoperatively.