'Adjuvant' drug lowers anesthetic dose

FOR patients undergoing surgery, adding a sedative drug called dexmedetomidine can not only lower the anesthetic dose but also delay the time until strong pain relievers are needed after surgery, reports a study in the April issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

The study using dexmedetomidine as an adjuvant agent was conducted by Dr. Marc Fischler of H?pital Foch, Suresnes, France, and colleagues. It included 60 patients undergoing surgery and anesthesia with two widely used intravenous anesthetic drugs: propofol and remifentanil. Patients were randomly assigned to receive the commonly used sedative drug dexmedetomidine, or an inactive placebo (saline solution).

Read the article in Anesthesia & Analgesia

The doses of propofol and remifentanil required for surgery were compared between groups. The anesthetics were given through an automated "closed-loop" system, which adjusted doses according to a measure of brain activity (the bispectral index) to precisely maintain a target level of anesthesia. This provided an objective measure of depth of anesthesia, minimizing variations in anesthetic dose.

The amounts of anesthetic drugs needed to induce anesthesia were significantly lower in patients receiving dexmedetomidine. The propofol induction dose was 30% lower and the remifentanil induction dose 25% lower, compared to patients receiving placebo.

The propofol dose needed to maintain the desired level of anesthesia was also about 30 percent lower in the dexmedetomidine group. The maintenance remifentanil dose was unaffected by dexmedetomidine.

Controlling pain after surgery

There was also evidence of an analgesic effect of dexmedetomidine. The median time to the first patient request for morphine was four hours after surgery in the dexmedetomidine group, compared to one hour in the placebo group.

There was no difference in recovery time, and no increase in the rate of delayed recovery, among patients receiving dexmedetomidine. Other adverse effects were also similar in the dexmedetomidine and placebo groups.

Dexmedetomidine is commonly used as a sedative for patients receiving mechanical ventilation in the intensive care unit. An alpha-2 adrenergic agonist, dexmedetomidine acts through a different mechanism than propofol or other anesthetics, suggesting that it might be a useful supplement for anesthesia.

While previous studies have shown that dexmedetomidine can reduce anesthetic and analgesic doses in patients undergoing surgery, this new study is the first to show an "anesthetic-sparing" effect using the bispectral index as an objective measure of anesthetic requirements.

The results of this randomized trials show that a relatively low dose of dexmedetomidine can reduce anesthetic dose while also helping to control pain after surgery, without prolonging recovery time. "Dexmedetomidine is a useful adjuvant that reduces anesthetic requirement and provides postoperative analgesia," Dr. Fischler and coauthors conclude.