The early inhaled anesthetics suffered from stability problems, leading to explosions and operating room fires. By halogenating the ether and hydrocarbon anesthetics, the explosiveness and flammability of the drugs were diminished, and the number of operating room fires decreased. Halogenation clearly stabilizes the inhaled agent and all inhaled anesthetics used today contain halogens.
Sporadic reports of fires involving sevoflurane can be found in the literature.4-6 The operating room fires involving sevoflurane all involved the recapture process and recirculating equipment. In an attempt to decrease operating room personnel exposure to the volatile anesthetics being exhaled by the patient, as well as to reduce the acquisition costs of the drug, recirculating breathing apparatus were developed. These breathing apparatus are designed to capture the expired gas, remove the carbon dioxide, and then allow the patient to inhale the anesthetic gas again. Different carbon dioxide absorbents are used such as calcium hydroxide, barium hydroxide, and sodium hydroxide. When the absorbent inadvertently dries out, as a result of the continuous flow of fresh gas, sevoflurane can break down and produce hydrogen in an exothermic reaction. The generation of hydrogen and heat may have been responsible for the reported fires that began in the anesthetic equipment.6 Other anesthetics have not had this same problem but all are monitored for their degradation products when exposed to carbon dioxide absorbents. Toxic metabolites of the inhaled anesthetics, such as the fluoride anion, are also a concern and discussed in the individual drug monographs.
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