Sevoflurane

Sevoflurane (2,2,2-trifluoro-1-[trifluoromethyl] fluoromethyl ether), also called fluoromethyl, is a sweet-smelling, non-flammable, highly fluorinated methyl isopropyl ether used for induction and maintenance of general anaesthesia. Together with desflurane, it is replacing isoflurane and halothane in modern anaesthesiology. It is often administered in a mixture of nitrous oxide and oxygen. After desflurane it is the volatile anaesthetic with the fastest onset and offset. Though desflurane has the lowest blood/gas coefficient of the currently used volatile anaesthetics, sevoflurane is the preferred agent for mask induction due to its lesser irritation to mucous membranes.

Though it vaporizes readily, it is a liquid at room temperature and is administered via an anaesthetic vaporizer attached to an anaesthetic machine.

It was introduced into clinical practice initially in Japan in 1990.

In contact with the soda lime in a rebreathing apparatus that serves as carbon dioxide absorber sevoflurane forms at least two degradation products, Compound A [fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether] and Compound B [1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane], especially at higher temperatures and when the soda lime is desiccated. Compound A has been shown to cause renal necrosis in rats. In humans, direct histological evidence of renal toxicity has not been demonstrated, although there is dose-related proteinuria, glycosuria and enzymuria. During low-flow anaesthesia, when the lower fresh gas flow leads to decreased flushing of the circuit and increased temperature of the soda lime, Compound A may build up to clinically significant levels. As a result, sevoflurane is sometimes administered with a minimum fresh gas flow of 2 liters per minute, making it a relatively expensive choice for maintaining general anaesthesia.

Physical properties

Boiling point: 58.6 °C (at 101.325 kPa)

Density: 1.517-1.522 g/cm³ (at 20 °C)

MAC : 2 vol % 

Molecular Weight: 200 u 

Vapor pressure: 157 mmHg (20.9 kPa) (at 20 °C)

 197 mmHg (26.3 kPa) (at 25 °C)

 317 mmHg (42.3 kPa) (at 36 °C)

Blood:Gas Partition Coefficient: 0.6 

Oil:Gas Partition Coefficient: 47

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