Analgesic and hypnotic effects of subanaesthetic concentrations of xenon in human volunteers: comparison with nitrous oxide.

The purpose of this study was to examine the effects of xenon and nitrous oxide in equipotent doses of 0.3 MAC on pain threshold and auditory response time in six healthy male volunteers. Compared with 100% oxygen inhalation, xenon and nitrous oxide significantly increased the pain threshold as measured by a radiant heat algometer. There was no significant difference in analgesic effects between xenon and nitrous oxide. Xenon significantly prolonged the response time to auditory stimuli compared with 100% oxygen, but nitrous oxide did not. The inhibitory effect of xenon on the auditory response time was significantly greater than that of nitrous oxide. The same six volunteers were studied to test if naloxone antagonized analgesia induced by xenon or nitrous oxide. The analgesic effects of xenon and nitrous oxide did not differ with or without naloxone.