XENON-THE STRANGER🌪

🍭colorless, odourless, tasteless gas

🍭four times denser than air. 

🍭density and viscosity are substantially higher than those of other inhalational anaesthetics. 

🍭occurs in extremely low concentrations (0.0875 ppm) in the atmosphere, hence its name from the Greek ‘xenos’ meaning ‘stranger’. 

🍭Xenon has been used experimentally as an anaesthetic for more than 50 years 

🍭Recently there has been a renewed interest in xenon as a safe, effective and more environmentally friendly substitute for nitrous oxide (Sanders et al. 2003). 

🍭manufactured by fractional distillation of liquefied air, currently at a cost of US $10 per litre (i.e. about 2,000 times the cost of producing N2O). This high cost is the major factor limiting its more widespread use, even when used in low-flow delivery systems. 

🍭Xenon has many of the properties of an ideal anaesthetic. 

🍭Its blood/gas partition coefficient (0.12) is lower than that of any other anaesthetic, giving rapid induction and emergence. 

🍭It is unlikely to be involved in any biochemical events in the body, and is not metabolised. 

🍭Xenon causes no significant changes in myocardial contractility, blood pressure or systemic vascular resistance, even in the presence of severe cardiac disease (Sanders et al. 2005). 

🍭The unique combination of analgesia, hypnosis, and lack of haemodynamic depression in one agent would make xenon a very attractive choice for patients with limited cardiovascular reserve 

🍭In contrast to other inhaled anaesthetic agents, xenon slows the respiratory rate and increases the tidal volume, thereby maintaining minute ventilation constant. 

🍭Airway pressure is increased during xenon anaesthesia, due to its higher density and viscosity rather than direct changes in airway resistance (Baumert et al 2002). 

🍭Because of its high cost xenon must be used in low-flow closed circuits. Crucial to this method of administration is accurate measurement of the concentration of xenon in the circuit. This measurement is generally difficult as xenon is  diamagnetic and does not absorb infrared radiation (commonly used to measure the  concentrations of other agents), and its low reactivity precludes the use of specific fuel cell or electrode-type devices. 

🍭Xenon conducts heat better than other gases, and a technique based on thermal conductivity has proved to be effective (Luginbuhl et al 2002). 

🍭Because xenon is heavier than air, the speed of sound is slower in xenon than that in air, and this difference has been also been used to measure xenon concentration. 

🍭Because xenon is a normal constituent of the atmosphere, it does not add to atmospheric pollution when emitted from the anaesthesia circuit. This is in contrast to the other inhalational anaesthetics, which have ozone-depleting potential and pollute the atmosphere when released from the anaesthesia system (Marx et al. 2001). 

🍭On a molecular basis, N2O is 230 times more potent as a greenhouse gas than carbon dioxide. N2O released as a waste anaesthetic contributes roughly 0.1% of total global warming. The lifetime of N2O in the atmosphere is long—approximately 120 years. 

🍭The anaesthetic actions of xenon are thought to result primarily from noncompetitive inhibition of  NMDA receptors (De Sousa et al. 2000), a property it shares with nitrous oxide. 

🍭In common with other NMDA receptor antagonists, xenon appears to have neuroprotective properties (Sanders et al. 2003). 

🍭Xenon is also an excellent analgesic, an action mediated by NMDA receptors (De Sousa et al. 2000). 

🍭Xenon also inhibits the plasma membrane Ca 2+   pump, altering neuronal excitability and inhibiting the nociceptive responsiveness of spinal dorsal horn neurones. 

(Reference : Jürgen Schüttler •  Helmut Schwilden Modern Anesthetics ,Handbook of Experimental Pharmacology, vol 182)