Nitrous Oxide

• Clinical Considerations
  • Nonpungent
  • Low blood: gas coefficient allows for titration
• Cerebral
  • ↑ CMRO₂
  • ↑ CBF
• Cardiovascular
  • Minimal
  • Higher concentrations (>60%) [2]
    • ↑ HR
    • ↑ SV
    • ↑ MAP
  • May attenuate hemodynamic depressant effects of halogenated volatile agents
• Pulmonary
  • Least effect of the volatile agents
  • ↓ TV
  • ↑ RR
  • No change in minute ventilation unlike other volatile agents
• Renal
  • Minimal
• Hepatic
  • Minimal
• Neuromuscular
  • Not a triggering agent for malignant hyperthermia
• Contraindications
  • Pneumothorax
  • Small bowel obstruction
  • Otitis media
  • Air embolism
  • First trimester of pregnancy
  • Intraocular surgery with gas bubbles
    • No current guidelines on how long after the eye injection nitrous oxide administration should wait [5]
  • B₁₂ deficiency and methyl tetrahydrofolate reductase deficiency
    • Debatable, but consider avoiding in this population [6]
• Board Facts
  • Prolonged N₂O can cause vitamin B₁₂ deficiency and peripheral sensory and motor dysfunction, especially in chronic nitrous oxide abusers [7]
  • May increase risk of PONV especially at high concentrations [8]
  • Diffuses into endotracheal tube cuff over procedure and can lead to tracheal morbidity [9]
    • Consider inflating cuff with saline instead of air
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