Administration of sevoflurane using other agent-specific vaporizers.

Abstract

The current study investigated the concentration of sevoflurane that could be achieved when sevoflurane was administered using standard agent-specific halothane, isoflurane, and enflurane vaporizers. An artificial lung analog model was made by attaching the 3-L reservoir bag to the 15-mm end of the anesthesia circle system. The lung analog was attached and ventilated with oxygen and air at flow rates of 2 L/min each (total gas flow = 4 L/min), a tidal volume of 800 mL, a rate of 10 breaths/min, and an inspiratory-to-expiratory ratio of 1:2. The vaporizer was filled with sevoflurane and the dial turned to 1%. After a 10-minute equilibration period, the concentration of sevoflurane was measured. The vaporizer concentration was increased in 1% increments, and after a 10-minute equilibration, the sevoflurane concentration was recorded. The dial was increased from 1% to 5% for the halothane and isoflurane vaporizer and from 1% to 7% for the enflurane vaporizer. Each study was repeated five times at each incremental increase of 1% for each of the three vaporizers. The series of studies were repeated using a total gas flow of 8 L/min (oxygen 4 and air 4) instead of 4 L/min (oxygen 2 and air 2). Using the halothane or isoflurane vaporizers at the 5% setting, the maximum sevoflurane concentrations achieved were 3.0% and 3.1%, respectively. The sevoflurane concentration was a maximum of 6% using the enflurane vaporizer set at 7%. The sevoflurane concentration decreased significantly when using any of the three vaporizers at all concentrations when the gas flow was increased from 4 to 8 L/min. The current study demonstrates that clinically useful concentrations of sevoflurane can be achieved with the administration of sevoflurane through an enflurane vaporizer. Although this is not routinely recommended, in specific circumstances it may allow the use of sevoflurane in third-world countries if sevoflurane vaporizers are not available and the use of sevoflurane is clinically necessary.