Desflurane

Desflurane

Systematic (IUPAC) name
2-(difluoromethoxy)-1,1,1,2-tetrafluoro-ethane
Pharmacokinetic data
Metabolism	Not metabolized
Biological half-life	Elimination dependent on minute ventilation
Identifiers
CAS Number	57041-67-5 Y
ATC code	N01AB07 (WHO)
PubChem	CID: 42113
IUPHAR/BPS	7156
DrugBank	DB01189 Y
ChemSpider	38403 Y
UNII	CRS35BZ94Q Y
KEGG	D00546 Y
ChEBI	CHEBI:4445 Y
ChEMBL	CHEMBL1200733 N
Chemical data
Formula	C3H2F6O
Molecular mass	168.038 g/mol
SMILES FC(F)(F)C(F)OC(F)F
InChI InChI=1S/C3H2F6O/c4-1(3(7,8)9)10-2(5)6/h1-2H Y Key:DPYMFVXJLLWWEU-UHFFFAOYSA-N Y
NY (what is this?)  (verify)

Desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane, enflurane, and isoflurane, it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Together with sevoflurane, it is gradually replacing isoflurane for human use, except in economically undeveloped areas, where its high cost precludes its use. It has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood.

Some drawbacks of desflurane are its low potency, its pungency and its high cost. It may cause tachycardia and airway irritability when administered at concentrations greater than 10 vol%. Due to this airway irritability, desflurane is infrequently used to induce anesthesia via inhalation techniques.

Though it vaporises very readily, it is a liquid at room temperature. Anaesthetic machines are fitted with a specialized anaesthetic vaporiser unit that heats liquid desflurane to a constant temperature. This enables the agent to be available at a constant vapor pressure, negating the effects fluctuating ambient temperatures would otherwise have on its concentration imparted into the fresh gas flow of the anesthesia machine.

Desflurane, along with enflurane and to a lesser extent isoflurane, has been shown to react with the carbon dioxide absorbent in anesthesia circuits to produce detectable levels of carbon monoxide through degradation of the anesthetic agent. The CO₂ absorbent Baralyme, when dried, is most culpable for the production of carbon monoxide from desflurane degradation, although it is also seen with soda lime absorbent as well. Dry conditions in the carbon dioxide absorbent are conducive to this phenomenon, such as those resulting from high fresh gas flows.

Pharmacology

Desflurane is known to act as a positive allosteric modulator of the GABA_A and glycine receptors, and as a negative allosteric modulator of the nicotinic acetylcholine receptor, as well as affecting other ligand-gated ion channels.

Physical properties

Boiling point :	23.5 °C or 74.3 °F	(at 1 atm)
Density :	1.465 g/cm³	(at 20 °C)
Molecular Weight :	168
Vapor pressure:	88.5 kPa	672 mmHg	(at 20 °C)
	107 kPa	804 mmHg	(at 24 °C)
Blood:Gas partition coefficient:	0.42
Oil:Gas partition coefficient :	19
MAC :	6 vol %

Global-warming potential

Desflurane is a greenhouse gas. Anesthesia gases used globally contribute the equivalent of 1 million cars to global warming. The twenty-year global-warming potential, GWP(20), for desflurane is 3714, meaning that one tonne of desflurane emitted is equivalent to 3714 tonnes of carbon dioxide in the atmosphere, much higher than sevoflurane or isoflurane. Taking into account the different amounts typically used in 1 hour of anesthesia (1 minimal alveolar concentration-hour), desflurane causes 26.8 times the global warming of sevoflurane.

Research

A recent clinical study found that desflurane has lower bispectral index and greater hypnotic effect than sevoflurane during the equipotent anesthesia.

References

Book references and additional reading

• Eger, Eisenkraft, Weiskopf. The Pharmacology of Inhaled Anesthetics. 2003.
• Rang, Dale, Ritter, Moore. Pharmacology 5th Edition. 2003.
• Martin Bellgardt: Evaluation der Sedierungstiefe und der Aufwachzeiten frisch operierter Patienten mit neurophysiologischem Monitoring im Rahmen der Studie: Desfluran versus Propofol zur Sedierung beatmeter Patienten. Bochum, Dissertation, 2005 (pdf)
• Susanne Lohmann: Verträglichkeit, Nebenwirkungen und Hämodynamik der inhalativen Sedierung mit Desfluran im Rahmen der Studie: Desfluran versus Propofol zur Sedierung beatmeter Patienten. Bochum, Dissertation, 2006 (pdf)
• Patel SS, Goa KL. (1995) "Desflurane. A review of its pharmacodynamic and pharmacokinetic properties and its efficacy in general anaesthesia." Drugs Oct;50(4):742-67. PMID 8536556.