Desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether), under the brand name Suprane, is a highly fluorinated methyl ethyl ether used for induction and maintenance of general anesthesia. It was developed in the 1980s and approved by the FDA in 1992 as a faster acting and clearing inhalant anesthetic compared to previously used inhalant anesthetics. Like halothane, enflurane, and isoflurane, it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Additionally, it has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood. It is also lipophobic and hydrophobic, and therefore does not easily dissolve in blood.
Some drawbacks of desflurane are its low potency, its pungency, and its high cost (though at low flow fresh gas rates, the cost difference between desflurane and isoflurane appears to be insignificant). It may cause tachycardia and airway irritability when administered at concentrations greater than 10% by volume. Due to this airway irritability, desflurane is infrequently used to induce anesthesia via inhalation techniques.
Though it vaporizes very readily, it is a liquid at room temperature. Desflurane has a high vapor pressure and a low boiling point, requiring a specific anesthetic vaporizer.
Medical uses
Desflurane is a volatile inhalational anesthetic primarily used for the maintenance of general anesthesia in adults and for maintenance in pediatric patients after induction with other agents. Unlike intravenous anesthetics, inhalation anesthetics allow for better and more rapid control over the concentration, therefore more control over the depth of anesthesia. In addition, elimination is more rapid, resulting in shorter spans of respiratory depression. Desflurane is favored for its very rapid onset and offset of action, enabling swift induction and particularly fast recovery, which is advantageous for outpatient and day-case surgeries, and in populations where rapid emergence is critical, such as the elderly and obese patients. Desflurane has a low blood solubility because it is hydrophobic and lipophobic, which is why it has a fast onset and elimination
Adverse effects
Most common side effect of inhalant anesthetics is postoperative nausea and vomiting (PONV). Desflurane can cause increased intracranial pressure.
Contraindications
It is contraindicated for induction of general anesthesia in the non-intubated pediatric population due to the high risk of laryngospasm. It should not be used in patients with known or suspected susceptibility to malignant hyperthermia. It is also contraindicated in patients with elevated intracranial pressure.
Pharmacology
the exact mechanism of the action of general anaesthetics has not been delineated. Inhalant anesthetics work on the central and peripheral nervous systems by blocking excitatory ion channels and enhancing the activity of inhibitory ion channels, and reducing pain signals by inhibiting of spinal cord dorsal horn neurons. In addition, desflurane acts as an antagonist on excitatory glutamate receptors, as a negative allosteric modulator of the nicotinic acetylcholine receptor, as well as affecting other ligand-gated ion channels.
Desflurane induces a dose dependent reduction in blood pressure due to reduced systemic vascular resistance. However, rapid increases in desflurane may induce a transient sympathetic response secondary to catecholamine release. Even though it is highly pungent, it is still a bronchodilator. It reduces the ventilatory response to hypoxia and hypercapnia. Like sevoflurane, desflurane vasodilatory properties also cause it to increase intracranial pressure and cerebral blood flow. However, it reduces cerebral metabolic rate. It also promotes muscle relaxation and potentiate neuromuscular blockade at a greater level than sevoflurane.
{| class="wikitable" style="text-align:center"
|- class="hintergrundfarbe6"
! colspan="2"| Enantiomeres of desflurane
|-
| class=skin-invert-image|180 px|Structural Formula of (R)-Desfluran<br /><small>(R)-Enantiomer</small>
| class=skin-invert-image|180 px|Structural Formula of (S)-Desfluran<br /><small>(S)-Enantiomer</small>
|}
Physical properties
{|
|Boiling point : ||align=right| 23.5 °C or 74.3 °F ||(at 1 atm)
|-
|Density : || 1.465 g/cm<sup>3</sup>|| (at 20 °C)
|-
|Molecular Weight : ||align=right| 168 Daltons||
|-
|Vapor pressure: ||align=right| 88.5 kPa ||align=right| 672 mmHg|| (at 20 °C)
|-
| ||align=right| 107 kPa ||align=right|804 mmHg || (at 24 °C)
|-
|Blood:Gas partition coefficient: ||align=right| 0.42 ||
|-
| Oil:Gas partition coefficient : ||align=right| 19 ||
|-
|MAC : ||align=right| 6 vol % ||
|-
|}
Global-warming potential
As desflurane is a polyfluorinated ether, it is a greenhouse gas. The twenty-year global-warming potential, GWP(20), for desflurane is about 3700, meaning that one tonne of desflurane emitted is equivalent to 3700 tonnes of carbon dioxide in the atmosphere, much higher than sevoflurane or isoflurane. Sevoflurane and isoflurane are replacing desflurane globally as hospitals try to minimize their carbon footprint. It has been estimated that halogenated anaesthetic agents used by health systems covering 80% of global population in 2023 emitted about 2 million tonnes CO2eq, 70% stemming from desflurane. England, Scotland and parts of Canada have banned desflurane use (except in exceptional circumstances) due to its environmental impact.
However unlike nitrous oxide, which is also used as an anaesthetic and remains in the atmosphere for over a century, the atmospheric lifetime of desflurane at 14.1 years is similar to methane at 12.4 years. Some argue that GWP is not a suitable metric for such short lived climate pollutants, and that due to its negligible radiative forcing desflurane is not a significant part of greenhouse gas emissions from the healthcare sector.
References
Further reading
- )