FRCA Notes

Xenon

  • Xenon is an inert noble gas that makes up 0.0000087% of the atmosphere
  • It has no occupational or environmental hazards
  • It has 9 isotopes: 7 stable and 2 radioactive isotopes


MAC Blood:gas coefficient Oil:gas coefficient Molecular weight Boiling point Critical temperature Safe ppm
71% 0.114 1.9 262 -108ºC 16.6ºC -
  • Non-flammable
  • Odourless
  • No greenhouse gas effects

Manufacture

  • Manufactured by the fractional distillation of air
  • Costs approximately 2,000x that of producing nitrous oxide

Elimination

  • Does not undergo metabolism but is eliminated 100% via the lungs

Respiratory

  • In contrast to other anaesthetic agents it causes increased VT
  • Reduces respiratory rate and can cause apnoea at high concentrations
  • It has a 3x higher density and 1.5x higher viscosity than nitrous oxide and as such may increase airway resistance in high concentrations
  • Doesn't cause diffusion hypoxia

Cardiovascular

  • Small reduction in HR due to vagotonic action
  • Doesn't alter myocardial contractility
  • Has ischaemic pre-conditioning effects on the heart

Neurological

  • Non-competitive antagonist at NMDA receptor
  • Increases CBF in a variable manner:
    • 135Xe may be used to measure CBF
    • May be used to enhance CT images of the brain
  • Significant analgesic properties
  • Some neuroprotective effects (BJA, 2022)