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Absorbents differ enormously in their capacity to produce compound A and carbon monoxide
C R Stabernack1, R Brown, M J Laster
1Department of Anesthesia, University of California, San Francisco, California 94143-0464, USA.
Unlabelled:
Concern persists regarding the production of carbon monoxide (CO) and Compound A from the action of carbon dioxide (CO(2)) absorbents on desflurane and sevoflurane, respectively. We tested the capacity of eight different absorbents with various base compositions to produce CO and Compound A. We delivered desflurane through desiccated absorbents, and sevoflurane through desiccated and moist absorbents, then measured the resulting concentrations of CO from the former and Compound A from the latter. We also tested the CO(2) absorbing capacity of each absorbent by using a model anesthetic system. We found that the presence of potassium hydroxide (KOH) and sodium hydroxide (NaOH) increased the production of CO from calcium hydroxide (Ca[OH](2)) but did not consistently affect production of Compound A. However, the effect of KOH versus NaOH was not consistent in its impact on CO production. Furthermore, the effect of KOH versus NaOH versus Ca(OH)(2) was inconsistent in its impact on Compound A production. Two absorbents (Amsorb) [Armstrong Medica, Ltd, Coleraine, Northern Ireland], composed of Ca(OH)(2) plus 0.7% polyvinylpyrrolidine, calcium chloride, and calcium sulfate; and lithium hydroxide) produced dramatically lower concentrations of both CO and Compound A. Both produced minimal to no CO and only small concentrations of Compound A. The presence of polyvinylpyrrolidine, calcium chloride, and calcium sulfate in Amsorb appears to have suppressed the production of toxic products. All absorbents had an adequate CO(2) absorbing capacity greatest with lithium hydroxide.
Implications:
Production of the toxic substances, carbon monoxide and Compound A, from anesthetic degradation by carbon dioxide absorbents, might be minimized by the use of one of two specific absorbents, Amsorb (Armstrong Medica, Ltd., Coleraine, Northern Ireland) (calcium hydroxide which also includes 0.7% polyvinylpyrrolidine, calcium chloride, and calcium sulfate) or lithium hydroxide.