Inadvertent change of volatile anesthetics in anesthesia machines.

Each month for 4 months, the contents of the enflurane and halothane vaporizers of 25 North American Dräger anesthesia machines were analyzed for enflurane and halothane by gas liquid chromatography. On five occasions a mixture of the two agents was found in a vaporizer. Such a mixture may lead to the unknowing delivery of markedly different anesthetic concentrations than expected and may endanger the patient. Analysis of the contents of 35 vaporizers of Ohio and Foregger machines did not show any case of accidental filling with the wrong agent. The vaporizers of the Ohio and Foregger machines are conspicuously different in appearance and location, while the similar appearance of the two vaporizers of the Dräger machine may have contributed to the mistakes in filling. We conclude that standard-keyed filling devices for volatile anesthetics are desirable.