Xenon: no stranger to anaesthesia.

Xenon derives its name from the Greek for `stranger' because of its rarity, representing no more than 8.75 3 10% of the atmosphere or 0.0875 ppm. Discovered in 1898, it is manufactured by fractional distillation of air and is used commercially for lasers, high intensity lamps, ̄ash bulbs, jet propellant in the aerospace industry, X-ray tubes, and in medicine. The total amount of xenon in the atmosphere would occupy around 10 litres at atmospheric pressure, which is more than 10 million times the amount currently produced each year. Xenon has been used experimentally in clinical anaesthetic practice for more than 50 yrs. Over this period of time, reports of clinical studies reveal that several hundred surgical patients have successfully received this noble gas as part of their anaesthetic regimen. Xenon's safety and ef®cacy pro®le in this setting appears to be unequalled and only its relatively high cost has precluded its more widespread clinical use. Concerns over cost are now being mitigated by technological developments in the delivery and recycling of xenon that will permit much less total gas to be expended for each anaesthetic administration. Over the last decade there has been renewed interest in the use of xenon as an anaesthetic, as investigators have sought to ®nd a safe and effective substitute for nitrous oxide, which has caused environmental concerns because of its ozone-depleting properties. Since then, studies have demonstrated several advantages of using xenon when compared with not only nitrous oxide, but most other potent inhalation agents. These include: 1. A pharmacokinetic bene®t as a result of its extremely low blood/gas partition coef®cient, which results in a rapid onset and offset of its action. 46 2. Less cardiovascular depression. 10 33 35 3. Neuroprotection. 64 4. Profound analgesia. 48 This review will deal with some of the bene®ts of xenon anaesthesia, with a view to identifying those areas where it may be used to clinical advantage.