Information ⬇
- Compound A
- Sevoflurane undergoes base catalyzed degradation in carbon dioxide absorbents to form a vinyl ether designated as compound A (Fig. 17-13: Compound a levels produced from three carbon dioxide absorbents during 1 minimum alveolar concentration sevoflurane anesthesia delivered at a fresh gas flow of 1 L/min (mean not equal to SE)). The production of compound A is enhanced in low-flow and closed-circuit breathing systems and by warm or very dry carbon dioxide absorbents.
- Species differences are present in the threshold for compound A–induced nephrotoxicity. (The β-lyase–dependent metabolism pathway for compound A breakdown to cysteine-S conjugates is less in humans than rats.) There is a high probability that renal injury in patients receiving sevoflurane does not occur regardless of the fresh gas flow rate.
- Carbon Monoxide and Heat
- Carbon dioxide absorbents degrade sevoflurane, desflurane, isoflurane, and isoflurane to carbon monoxide (patients at risk for carbon monoxide intoxication) when carbon dioxide absorbent has become desiccated (water content <5%).
- The degradation is the result of an exothermic reaction of the anesthetics with the absorbent.
- Instances of carbon monoxide poisoning have occurred when the carbon dioxide absorbent has been presumably desiccated because an anesthetic machine has been left on with a high fresh gas flow passing through the carbon dioxide absorbent over an extended period.
- Although desflurane produces the most carbon monoxide with anhydrous carbon dioxide absorbents, the reaction with sevoflurane produces the most heat. This is an exothermic reaction with the potential for fires and patient injuries.
- Although sevoflurane is not flammable at <11%, formaldehyde, methanol, and formate may result from degradation at high temperatures and when combined with oxygen may be flammable.
- Generic Sevoflurane Formulations. Although the generic formulations of sevoflurane are chemically equivalent, the water content of the formulations differs, resulting in different resistance to degradation to hydrogen fluoride when exposed to Lewis acids (metal halides and metal oxides that are present in modern vaporizers).
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