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October 16, 2007
9:00 AM - 11:00 AM
Room Hall D, Area G,
Sevoflurane Vaporizers Contain Lewis Acid Metal Oxides That Can Potentially Degrade Sevoflurane
Dennis A. Stephens, Ph.D., Evan D. Kharasch, M.D., Ph.D., Keith R. Cromack, Ph.D., Sanjay Shrivastava, Ph.D., Mario D. Saltarelli, M.D., Ph.D.
Department of Neuroscience and Anesthesia, Abbott Laboratories, Abbott Park, Illinois
Background: Sevoflurane exposure to Lewis acids, such as metal oxides, can cause sevoflurane degradation to hydrogen fluoride (HF) and other potential toxins. Water prevents such degradation and HF production, and sevoflurane (Abbott Ultane®) was reformulated in 1997 to contain >300 ppm water. Commercially marketed sevoflurane vaporizers may contain Lewis acids that could contact and potentially degrade sevoflurane that does not contain protective amounts of water. The purpose of this investigation was to identify and quantify potential Lewis acids and their sites of location within three commercially marketed sevoflurane vaporizers.

Materials and Methods: Three types of vaporizers (Draeger Vapor 2000, GE/Datex-Ohmeda Tec 7, and Penlon Sigma Elite), both new and old, were disassembled and examined by scanning electron microscopy, energy dispersive spectroscopy, and stereomicroscopy to determine which surfaces come into contact with sevoflurane (liquid or vapor) and which surfaces may contain potential Lewis acids. X-ray photoelectron spectroscopy and electron spectroscopy for chemical analysis was used to identify metal oxides, their oxidation state, and the surface depth of any oxides in contact with sevoflurane.

Results and Discussions:

Sevoflurane, both as liquid and vapor, is exposed to multiple potential Lewis acid contact sites within each vaporizer type. No substantial differences were observed between the new and used vaporizers.[table1]Conclusion(s): Potential Lewis acids were identified in all brands of vaporizers analyzed. If chemically active, potential Lewis acids in vaporizer components could lead to degradation of low-water sevoflurane formulations.

Acknowledgements: Supported by funding from Abbott Laboratories.

Anesthesiology 2007; 107: A1597
VaporizerSurface area of potential LA exposed to liquid (cm2)Surface area of potential LA exposed to vapor (cm2)
GE/Datex-Ohmeda Tec 7183189
Draeger Vapor 2000917481
Penlon Sigma Elite400429