COMPARISON OF THE ANALGESIC POTENCY OF XENON AND NITROUS-OXIDE IN HUMANS EVALUATED BY EXPERIMENTAL PAIN

We have compared the analgesic potency of MAC-equivalent concentration s of xenon (10, 20, 30 and 40%) and nitrous oxide (15, 30, 45 and 60%) in humans using a multimodal experimental pain testing and assessment technique. We tested 12 healthy volunteers in a randomized, single-bl ind, crossover study. The following experimental pain tests were used: nociceptive reflex to repeated stimuli; pain tolerance to maximal eff ort tourniquet ischaemia; electrical stimulation; mechanical pressure; and cold. Reaction time was also measured. Xenon and nitrous oxide pr oduced analgesia to ischaemic, electrical and mechanical stimulation, but not to cold pain. There was no difference in MAC-equivalent concen trations of xenon and nitrous oxide. Both increased reaction time in a similar manner. Xenon and nitrous oxide evoked nausea and vomiting in a large number of volunteers.