Xenon

Xenon is a dense, colourless gas found in the Earth's atmosphere in trace amounts. Cullen and Gross first reported the anaesthetic properties of xenon in humans in 1951. Xenon offers many advantages over nitrous oxide, for which it could theoretically become a suitable replacement. Unfortunately it is difficult to manufacture, which makes it extremely expensive, precluding its use in mainstream anaesthesia. However, anaesthetic machines with the ability to deliver xenon are likely to become available thanks to a mechanism by which xenon can be recovered and recycled, making it far more economical. Xenon, in common with nitrous oxide and ketamine, acts by non-competitive inhibition of NMDA receptors in the CNS.

Physical properties 

Xenon has a blood/gas partition coefficient of 0.14–0.2, which is lower than that of nitrous oxide (0.47) and therefore provides rapid induction of and recovery from anaesthesia. Xenon is more potent than nitrous oxide, with a MAC of 70%. It does not undergo biotransformation, and it is harmless to the ozone layer. 

Systemic effects 

Studies so far have found no cardiorespiratory adverse effects or reduction in local organ perfusion; in fact, to date it has demonstrated both cardio- and neuroprotective properties through a variety of mechanisms. It is not irritating to the respiratory tract. Xenon is a competitive inhibitor of the 5-HT3 receptor and is therefore thought to reduce the incidence of PONV.