Evaluation of antihyperalgesic and analgesic effects of 35% nitrous oxide when combined with remifentanil: A randomised phase 1 trial in volunteers

BACKGROUND Remifentanil is an effective drug in peri-operative pain therapy, but it can also induce and aggravate hyperalgesia. Supplemental administration of N2O may help to reduce remifentanil-induced hyperalgesia. OBJECTIVE To evaluate the effect of 35 and 50% N2O on hyperalgesia and pain after remifentanil infusion. DESIGN Single site, phase 1, double-blind, placebo-controlled, randomised crossover study. SETTING University Hospital, Germany from January 2012 to April 2012. PARTICIPANTS Twenty-one healthy male volunteers. INTERVENTIONS Transcutaneous electrical stimulation induced spontaneous acute pain and stable areas of hyperalgesia. Each volunteer underwent the following four sessions in a randomised order: 50 to 50% N2-O2 and intravenous (i.v.) 0.9% saline infusion (placebo); 50 to 50% N2-O2 and i.v. remifentanil infusion at 0.1 μg kg−1 min−1 (remifentanil); 35 to 15 to 50% N2O-N2-O2 and i.v. remifentanil infusion at 0.1 μg kg−1 min−1 (tested drug) and 50 to 50% N2O-O2 and i.v. remifentanil infusion at 0.1 μg kg−1 min−1 (gas active control). Gas mixtures were inhaled for 60 min; i.v. drugs were administered for 30 min. MAIN OUTCOME MEASURES Areas of pin-prick hyperalgesia, areas of touch-evoked allodynia and pain intensity on a visual analogue scale were assessed repeatedly for 160 min. RESULTS Data from 20 volunteers were analysed. There were significant treatment and treatment-by-time effects r...
Source: European Journal of Anaesthesiology - Category: Anesthesiology Tags: Perioperative medicine and pain Source Type: research