It is a newer all fluorinated congener of isoflurane which has gained popularity as an anaesthetic for out patient surgery. Though it is highly volatile, a thermostatically heated special vapourizer is used to deliver a precise concentration of pure desflurane vapour in the carrier gas (N,0 +0,) mixture. Its distinctive properties are lower lipid solubility as well as very low solubility in blood and tissues, because of which induction and recovery are very fast. Depth of anaesthesia changes rapidly with change in inhaled concentration giving the anaesthetist better control. Postanaesthetic cognitive and motor impairment is shortlived, so that patient can be discharged a few hours after surgery.

The mechanism of action of the inhalational agents is still unclear. Inhalational anesthetics are thought to work via interaction with different ion channels present throughout the central and peripheral nervous system by blocking excitatory channels and enhancing the activity of inhibitory channels. Other proposed mechanisms are that these agents work by affecting the membrane bilayer. The structure of desflurane is similar to that of isoflurane except for the addition of a fluorine atom. This addition changes the physical properties of desflurane compared to other inhalational agents. The vapor pressure of desflurane at 20 degrees Celsius is 681 mm Hg, with a boiling point of 22.8 degrees Celsius. Desflurane requires the use of a temperature-controlled, pressure-regulated vaporizer, as opposed to a variable bypass vaporizer. The molecular weight of desflurane is 168 grams, and a very small percentage of the anesthetic is metabolized by the body compared to other inhalational agents.

Desflurane is 5 times less potent than isoflurane; higher concentration has to be used for induction, which irritates the air passage and may induce coughing, breath holding and laryngospasm. A somewhat pungent odour also makes it unsuitable for induction. Rapid induction sometimes causes brief sympathetic stimulation and tachycardia which may be risky in those with cardiovascular disease. The degree of respiratory depression, muscle relaxation, vasodilatation and fall in blood pressure are similar to that with isoflurane. Cardiac contractility and coronary blood flow are maintained. Lack of seizure provoking potential arrhythmogenicity and absence of liver as well as kidney toxicity are also similar to isoflurane. Desflurane is rapidly exhaled unchanged. As such, it can serve as a good alternative to isoflurane for routine surgery as well, especially prolonged operations. If closed circuit is used, the soda lime should be fresh and well hydrated to prevent formation of carbon monoxide. 

Desflurane, along with the other inhalational agents, sevoflurane and Isoflurane, is a potent vasodilator and can cause a decrease in blood pressure by decreasing systemic vascular resistance (SVR). A concomitant increase in heart rate sometimes occurs. Cardiac output is typically preserved with the use of this agent. Desflurane dilates cerebral arteries and causes a decrease in cerebral metabolic rate. Desflurane also causes an increase in intracranial pressure (ICP), like other inhalational anesthetics. This increase in intracranial pressure can be targeted by hyperventilation and hypocapnia in a patient as carbon dioxide (CO2) autoregulation is maintained with use. There is also a dose related depression in electroencephalogram (EEG) activity with the use of desflurane. When used to maintain anesthesia in the pediatric population, after induction with another inhalational agent, desflurane was associated with an increased rate of emergence delirium.

Rapid increases in desflurane concentration can cause a transient but clinically significant elevation in heart rate and blood pressure. These effects are secondary to catecholamine release, which is more pronounced with desflurane than isoflurane or sevoflurane. This resulting sympathetic response is controllable by concurrent administration of esmolol, clonidine, or the use of an opioid. Slowing the rate of increase in the concentration of desflurane can also decrease the catecholamine release. Volatile anesthetics promote skeletal muscle relaxation and enhance the effects of neuromuscular blocking agents. Desflurane enhances the effects of rocuronium, greater than either sevoflurane, isoflurane, or intravenous anesthetics. As with all inhaled anesthetics, there is a decrease in the ventilatory response to carbon dioxide.

Desflurane contraindications include induction of anesthesia in nonintubated pediatric patients because of a high incidence of moderate to severe upper airway adverse events. Pediatric patients are at high risk of laryngospasm. Desflurane is also contraindicated in patients with known or suspected susceptibility to malignant hyperthermia. If the patient has a history of moderate to severe hepatic impairment following general anesthesia with desflurane, the use of desflurane should be avoided. Additionally, if a patient has intracranial hypertension, desflurane is contraindicated, as is the case with all such volatile agents.

Published : Oct 18 2023