• E I Eger.
• Department of Anesthesia, University of California, San Francisco 94143-0464.
• Anesth. Analg. 1992 Oct 1;75(4 Suppl):S3-7; discussion S8-9.

AbstractSubstitution of fluorine for the single chlorine atom in isoflurane produces the new anesthetic, desflurane. This seemingly small change produces several pharmacologic changes. The potency of desflurane (MAC equals 6.0% in middle-aged patients) is one-fifth that of isoflurane (1.15%), with MAC for each agent decreased by aging, hypothermia, or the addition of depressants such as midazolam, fentanyl, or nitrous oxide. Some properties are similar: desflurane and isoflurane both depress respiration and neuromuscular contractility, and higher concentrations (e.g., 6%-8% desflurane) of both agents have a pungency that can provoke breath holding, laryngospasm, and salivation, particularly in infants and children. Of great importance, the substitution of fluorine for chlorine markedly decreases blood (desflurane blood-gas partition coefficient 0.42) and tissue solubility (e.g., brain-blood partition coefficient 1.3) relative to isoflurane (values 1.4 and 1.6, respectively). As a result, desflurane alveolar concentrations may be adjusted more rapidly and precisely; desflurane enters and leaves the lungs and tissues more rapidly; and recovery is quicker both for the short (first 10-20 min) and long (0.5-1.5 h) term. This greater precision of control and more rapid recovery are consistent with trends for new drug development in anesthesiology.

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