CARBON-MONOXIDE PRODUCTION FROM DEGRADATION OF DESFLURANE, ENFLURANE,ISOFLURANE, HALOTHANE, AND SEVOFLURANE BY SODA LIME AND BARALYME(R)

Anecdotal reports suggest that soda lime and Baralyme(R) brand absorbe nt can degrade inhaled anesthetics to carbon monoxide (GO). We examine d the factors that govern CO production and found that these include: 1) The anesthetic used: for a given minimum alveolar anesthetic concen tration (MAC)-multiple, the magnitude of CO production (greatest to le ast) is desflurane greater than or equal to enflurane > isoflurane >> halothane = sevoflurane. 2) The absorbent dryness: completely dry soda lime produces much more CO than absorbent with just 1.4% water conten t, and soda lime containing 4.8% or more water (standard soda lime con tains 15% water) generates no CO. In contrast, both completely dry Bar alyme(R) and Baralyme(R) with 1.6% water produce high concentrations o f CO, and Baralyme(R) containing 4.7% water produces concentrations eq ualing those produced by soda Lime containing 1.4% water. Baralyme(R) containing 9.7% or more water and standard Baralyme(R) (13% water) do not generate CO. 3) The type of absorbent: at a given water content, B aralyme(R) produces more CO than does soda lime. 4) The temperature: a n increased temperature increases CO production. 5) The anesthetic con centration: more CO is produced from higher anesthetic concentrations. These results suggest that CO generation can be avoided for all anest hetics by using soda lime with 4.8% (or more) water or Baralyme(R) wit h 9.7% (or more) water, and by using inflow rates of less than 2-3 L/m in. Such inflow rates are low enough to ensure that the absorbent does not dry out.