Pharm 101: Nitrous Oxide

Class

Inhaled anaesthetic


Pharmacodynamics
  • Incomplete gaseous inhaled anaesthetic
    • Have high vapour pressures and low boiling points
    • Gas form at room temperature
  • Minimal Alveolar Concentration (MAC) > 100%
    • MAC is the anaesthetic concentration that produces immobility in 50% of patients exposed to a noxious stimulus
  • Mechanism of action not fully understood, thought to potentiate GABA-A receptors

Pharmacokinetics
  • Absorption through gas exchange in alveoli
  • Not metabolised
  • Low solubility, reaches high arterial tension rapidly
    • Low Blood:Gas partition coefficient 0.47
  • Rapid equilibrium in brain and fast onset of action
    • Rapid onset and recovery

Organ system effects
  • CNS:
    • Analgesia
    • Euphoria
    • Increased cerebral blood flow and ICP
  • CVS:
    • Dose-dependent myocardial depression
    • Preserved CO due to simultaneous sympathetic nervous system activation
  • Respiratory:
    • Bronchodilation
  • Renal:
    • Reduction in both GFR and renal blood flow, overall increase in filtration fraction

References

Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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