Some science behind the scenes

Xenon

Xenon is a colorless, heavy, odorless noble gas. It occurs in the Earth's atmosphere in trace amounts - 87±1 parts per billion (nL/L), or approximately 1 part per 11.5 million, and is also found in gases emitted from some mineral springs.

Xenon is obtained commercially as a byproduct of the separation of air into oxygen and nitrogen. After this separation, the liquid oxygen produced will contain small quantities of krypton and xenon. By additional fractional distillation steps, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which is extracted either via adsorption onto silica gel or by distillation. Finally, the krypton/xenon mixture may be separated into krypton and xenon via distillation.

Extraction of a litre of xenon from the atmosphere requires 220 watt-hours of energy.  For this reason it is expensive.

Xenon is used in flash lamps and arc lamps, and as a general anaesthetic.

Although Lazharev, in Russia, apparently studied xenon anaesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by J. H. Lawrence, who experimented on mice. Xenon was first used as a surgical anaesthetic in 1951 by Stuart C. Cullen, who successfully operated on two patients.

Its use as an anaesthetic, however, is due to increase considerably as, although it is expensive, advances in recovery and recycling of xenon have made it economically viable. Unlike nitrous oxide (N2O), xenon is not a greenhouse gas and so it is also viewed as environmentally friendly. Any Xenon vented into the atmosphere is being returned to its original source, so “no environmental impact is likely”.

Xenon is 50% more potent than N2O as an anaesthetic. Thus it can be used in concentrations with oxygen that have a lower risk of hypoxia.

Xenon is also in theory ‘non-toxic’. But of course it is viewed as non-toxic because it hasn’t been experimented on much and no clinical papers have yet emerged which show damage. And there are no reports of hallucinations, or out of body experiences, or anything like that either, which may mean it is relatively non-toxic.

One of the odd side effects is that it lowers the resonant frequencies of the vocal tract when inhaled. This produces a characteristic lowered voice timbre, an effect opposite to the high-timbred voice caused by inhalation of helium.

See website: Erowid.org

Background papers

Anasthesiol Intensivmed Notfallmed Schmerzther. 2007 Nov;42(11):784-91.
[Xenon--the ideal anaesthetic agent?]. - [Article in German] Bein B Höcker J, Scholz J.
Klinik für Anästhesiologie und Operative Intensivmedizin, Universitätsklinikum Schleswig-Holstein, Campus Kiel.
The noble gas xenon, besides its anaesthetic and analgesic properties, shows many characteristics of an ideal anaesthetic agent. However, due to high production costs, its application is limited In daily clinical routine.

Recent studies suggested not only outstanding haemodynamic stability and rapid emergence from anaesthesia, but also xenon's capacity to mediate protection against ischaemic damage in various organs and tissues.

Since xenon is devoid of toxicity and relevant side effects, it could be beneficial at least in a subset of patients at high risk, and xenon therefore may become a reasonable alternative in this patient population.

PMID: 18040933

Anesteziol Reanimatol. 2011 Mar-Apr;(2):4-7 [Low-flow xenon anesthesia in surgical patients with hypertension]. [Article in Russian]
Rashchupkin AB, Burov NE.
A comparative study of central hemodynamics in 60 patients with essential hypertension during low flow anesthesia with xenon and nitrous oxide is carried out. The main group consisted of 30 patients, 22 male and 8 female, in the median age of 45.9 +/- 23 years. 22 patients out of those had 2nd stage essential hypertension, while the other 8 had 3rd stage. The control group consisted of 30 patients, 20 male and 10 female, in the median age of 45.1 + 1.3 years. 4 patients had 3rd stage essential hypertension, 26 patients had 2nd stage. The both groups were clinically comparable by the character and severity of the main disease, the carried out surgery (open cholecystectomy) and the qualification of surgeons. Results of the research showed, that low flow monoanesthesia with xenon abruptly eradicated the unfavourable consequences of induction of anesthesia (3-5 mg/kg of sodium thiopental or 2-2.5 mg/kg of propofol) and had a positive effect on the parameters of central hemodynamics of patients with essential hypertension. Xenon anesthesia, compared to nitrous oxide, rapidly stabilized the parameters of blood pressure and heart rate and can be recommended as a method of choice in patients with essential hypertension and compromised myocarium. Nitrous oxide with bolus of regular fentanyl doses doesn't reliable anesthesiological protection during open cholecystectomy and shows signs of toxicity.

PMID: 21692217

Ann Fr Anesth Reanim. 2010 Sep;29(9):635-41. doi: 10.1016/j.annfar.2010.04.006. Epub 2010 Jul 27.
[Benefits and indications of xenon anaesthesia]. [Article in French] Delhaye O Robin E Bazin JE Ripart Lebuffe G Vallet B. Fédération d'anesthésie-réanimation, CHRU de Lille, rue Polonovski, Lille cedex, France.

OBJECTIVE:
To analyze the current knowledge related to xenon anaesthesia.

DATA SOURCES:
References were obtained from computerized bibliographic research (Medline), recent review articles, the library of the service and personal files.

STUDY SELECTION:
All categories of articles on this topic have been selected.

DATA EXTRACTION:
Articles have been analyzed for biophysics, pharmacology, toxicity and environmental effects, clinical effects and using prospect.

DATA SYNTHESIS:
The noble gas xenon has anaesthetic properties that have been recognized 50 years ago. Xenon is receiving renewed interest because it has many characteristics of an ideal anaesthetic. In addition to its lack of effects on cardiovascular system, xenon has a low solubility enabling faster induction of and emergence from anaesthesia than with other inhalational agents. Nevertheless, at present, the cost and rarity of xenon limits widespread use in clinical practice. The development of closed rebreathing system that allowed recycling of xenon and therefore reducing its waste has led to a recent interest in this gas.

CONCLUSION:
Reducing its cost will help xenon to find its place among anaesthetic agents and extend its use to severe patients with specific pathologies.

Copyright (c) 2010. Published by Elsevier SAS.
PMID: 20667685