Intraoperative low-dose naloxone reduced postoperative hyperalgesia but had no effect on pain when combined with high-dose remifentanil for elective thyroid surgery, in a recent study published in British Journal of Anesthesia.

Researchers randomly assigned 91 patients undergoing elective thyroid surgery to receive high-dose remifentanil (4 ng/mL) plus low-dose naloxone (0.05 µg/kg per hour), high-dose remifentanil plus placebo, or low-dose remifentanil (1 ng/mL) plus placebo. Pain thresholds and the incidence of hyperalgesia were evaluated 24 hours post-surgery. Pain intensity, analgesic consumption, and adverse events were measured 48 hours post-surgery.

At 24 hours, the pain threshold was significantly higher in the high-dose remifentanil-only group (median von Frey number 3.63) compared with the high-dose remifentanil group plus naloxone and the low-dose remifentanil-only groups (3.84 and 3.80, respectively; P =.01 for both).

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The incidence of hyperalgesia was higher in the high-dose remifentanil-only group compared with remifentanil plus naloxone or low-dose remifentanil (67.7% vs 33.3% vs 30%; P =.005). No difference was noted between the groups for postoperative pain intensity, analgesic consumption, or adverse events.

According to the study investigators, “the anti-hyperalgesic effect of naloxone is likely to be produced by antagonizing or modifying N-methyl-D-aspartate and µ-opioid receptor activities.” They concluded that “intraoperative use of low-dose naloxone combined with high-dose remifentanil reduced postoperative hyperalgesia compared with the use of remifentanil alone.”

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Koo CH, Yoon S, Kim BR, et al. Intraoperative naloxone reduces remifentanil-induced postoperative hyperalgesia but not pain: a randomized controlled trial [published online October 3, 2017]. Br J Anaesth. doi:10.1093/bja/aex253