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Inhalational anesthetics

Last updated: March 4, 2021

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Inhalational anesthetics are used for the induction and maintenance of general anesthesia as well as sedation. The exact mechanisms by which they act are still unknown. The most common inhalational anesthetics are sevoflurane, desflurane, and nitrous oxide. Of these, sevoflurane is the most common because of its rapid onset of action and the fact that patients recover quickly from it. Inhalational anesthetics cause respiratory depression, a decrease in arterial blood pressure and cerebral metabolic demand, and an increase in cerebral blood flow. While side effects differ based on the substance (e.g., halothane can cause hepatotoxicity), the most common side effect is nausea.

  • Inhalational anesthetics provide both analgesia and narcosis and can be used for induction and maintenance of general anesthesia.
  • The exact mechanism of action of inhalational anesthetics is still unknown.
  • The most widely used inhalational anesthetics are:
    • Nitrous oxide
    • Desflurane
    • Sevoflurane
    • Isoflurane
    • Enflurane (no longer marketed in the US)
    • Halothane (no longer marketed in the US)
    • Methoxyflurane


Pharmacokinetic principles

Pharmacodynamic principles

Pharmacokinetics and pharmacodynamics of common inhalational anesthetics


General effects

  • Anesthesia
  • Sedation/narcosis
  • ↓ Respiration
  • ↓ Arterial blood pressure
  • Myocardial depression
  • ↓ Cerebral metabolic demand
  • ↑ Cerebral blood flow
  • ↑ ICP
  • Postoperative: nausea and vomiting

Specific characteristics of common inhalational anesthetics

Specific characteristics
Nitrous oxide
  • Can cause expansion of gas trapped in a cavity
  • Usually insufficient if used alone → often combined with a more potent inhalational anesthetic to achieve the “second gas effect”
  • Rapid onset and recovery
  • Very rapid onset and recovery
  • Pungent odor; irritates airways → not suitable for induction of anesthesia
  • Most commonly used inhalational anesthetic
  • Rapid onset and recovery
  • Nonpungent → suitable for induction of anesthesia
  • Most potent of the fluranes
  • Relatively slow onset and recovery
  • Pungent odor → not suitable for induction of anesthesia
  • Seizures (proconvulsive)
  • Medium speed of onset and recovery
  • Hepatotoxicity
  • Medium speed of onset and recovery



We list the most important adverse effects. The selection is not exhaustive.

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