Current and future perspectives on inhaled anesthetics.

The discovery of ether anesthesia made modern surgery possible. Successive improvements produced today's inhaled anesthetics, compounds that allow precise control over the anesthetic state without compromising safety. Such control extends to induction and maintenance of, and recovery from, anesthesia. The greatest emphasis is on the last, particularly the rapid recovery obtained with anesthetics with low solubility in blood and tissues. The lowest solubility is produced by halogenation with fluoride to the exclusion of other halogens. The safety of anesthesia has many components. Important among these is molecular stability that permits elimination of the unchanged anesthetic molecule in expired air and provides resistance to degradation by metabolism and by carbon dioxide absorbents. Halogenation with fluorine produces more stable, safer anesthetics. Greater stability, lower solubility, and rapid recovery can decrease direct and indirect costs.