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Desflurane - MAC, Boiling point, blood gas coo efficient, oil gas coefficient mechanism of action indication and contraindications

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desflurane AND pharmacology

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desflurane prescribing information MAC blood gas partition coefficient boiling point contraindications

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https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?set…

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Desflurane

PropertyValue / significance
MACAbout 6% in a healthy adult at 1 atmosphere, oxygen. MAC decreases with increasing age and with concurrent opioids, benzodiazepines, nitrous oxide, etc. High MAC means it is relatively less potent than agents such as sevoflurane or isoflurane.
Boiling point22.8°C at 1 atm
Vapor pressure669 mmHg at 20°C. Its high vapor pressure and boiling point near room temperature require a dedicated heated, pressurized, electronically controlled vaporizer.
Blood-gas partition coefficient0.42 (commonly quoted 0.42-0.45 at 37°C)
Oil-gas partition coefficient18.7 at 37°C
MetabolismVery low, <0.1%. More than 99% is eliminated unchanged through the lungs.
Odor / airway effectPungent and airway-irritant. Can cause coughing, breath-holding, laryngospasm, and sympathetic stimulation if concentration is increased abruptly.
The manufacturer’s listed physical constants are blood-gas coefficient 0.424, olive-oil-gas coefficient 18.7, and boiling point 22.8°C. DailyMed prescribing information

Meaning of the coefficients

  • Low blood-gas coefficient (0.42): little desflurane dissolves in blood, so alveolar and brain partial pressures rise and fall quickly. This produces rapid induction, rapid emergence, and good titratability, especially after prolonged anesthetics.
  • Oil-gas coefficient (18.7): reflects lipid solubility and correlates broadly with anesthetic potency. Because its oil-gas solubility is modest, desflurane is less potent, hence its relatively high MAC.

Mechanism of action

Desflurane is a volatile halogenated ether general anesthetic. There is no single receptor mechanism. It produces hypnosis, amnesia, immobility, and unconsciousness through combined CNS effects:
  • Enhances inhibitory neurotransmission, including GABA-A and glycine receptor activity.
  • Activates background potassium channels, particularly two-pore-domain K+ channels, causing neuronal hyperpolarization.
  • Reduces excitatory synaptic transmission, including effects on NMDA receptors, presynaptic voltage-gated calcium channels, and neurotransmitter release.
  • Spinal cord actions are especially important for immobility in response to surgical stimulus.

Indications

  1. Induction and maintenance of general anesthesia in adults.
  2. Maintenance of general anesthesia in pediatric patients only after induction by another agent and after tracheal intubation.
  3. Particularly useful when rapid wake-up is desirable, for example:
    • Long operations
    • Obesity, because low blood solubility permits relatively fast recovery
    • Ambulatory anesthesia, when airway suitability permits
    • Situations requiring prompt postoperative neurological assessment
It is indicated for adult induction and/or maintenance, and for maintenance only in intubated pediatric patients after induction with another agent. DailyMed indications

Contraindications

Do not use desflurane in:
  1. Known or suspected susceptibility to malignant hyperthermia (MH), including relevant personal or family history.
  2. Patients in whom general anesthesia itself is contraindicated.
  3. Pediatric inhalational induction.
  4. Known hypersensitivity to desflurane or other halogenated anesthetic agents.
  5. Previous unexplained moderate to severe hepatic dysfunction, jaundice, fever, or eosinophilia after desflurane or another halogenated anesthetic.

Important cautions, not always absolute contraindications

  • Reactive airway disease or asthma: Avoid inhalational induction because desflurane is pungent and may provoke coughing, laryngospasm, bronchospasm, and increased airway resistance.
  • Coronary artery disease or severe ischemic heart disease: Rapid rises in concentration may cause tachycardia and hypertension from sympathetic activation, increasing myocardial oxygen demand. Do not use it as the sole induction agent where this is undesirable.
  • Raised intracranial pressure / intracranial mass lesion: Can raise cerebral blood flow and intracranial pressure. If used, employ controlled ventilation and generally keep concentration at or below 0.8 MAC as appropriate.
  • Risk of postoperative nausea and vomiting: Like other volatile anesthetics, it can contribute.
  • It can trigger malignant hyperthermia, particularly when combined with succinylcholine in susceptible people.
Exam memory line:
Desflurane = MAC 6%, blood-gas 0.42, oil-gas 18.7, boiling point 22.8°C, fastest volatile recovery, pungent airway irritant, dedicated vaporizer, avoid pediatric inhalational induction and MH susceptibility.
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