The degradation, absorption, and solubility of volatile anesthetics in soda lime depend on water content.

Abstract

Absorption of anesthetic into soda lime may delay induction of anesthesia and degradation by soda lime may produce toxic products. We determined whether the moisture content of soda lime influences the mechanisms underlying absorption (saturable uptake), degradation, and solubility (nonsaturable uptake). We placed liquid anesthetic (sevoflurane, isoflurane, halothane, enflurane, or desflurane) in 581-mL equilibration flasks containing soda lime of various water contents (0%-15.1% H2O) and sampled the vapor concentrations repeatedly for 24-35 h. Loss of vapor from the gas phase was partitioned into absorption, degradation, and solubility factors by regression analyses. We also found that soda lime in absorbers may dry from H2O contents of 15% to 4%-8.5% in routine clinical use. Our observations suggest that during induction of anesthesia a portion of the delivered anesthetic may be lost to the soda lime, rather than delivered to the patient. In addition, the potential for production of toxic products may be increased when volatile anesthetics are used with dry soda lime.