To the Editor:—

I read with interest the recent article by Knolle et al.  regarding the use of Amsorb (Armstrong, Coleraine, Northern Ireland) to detect the dehydration of conventional carbon dioxide (CO2) absorbents that contain strong bases. 1Amsorb is a new CO2absorbent, which does not  contain strong bases such as sodium or potassium hydroxide. 2The authors correctly note that the dehydration of strong base containing CO2absorbents cannot be detected in clinical practice, and this places patients undergoing general anesthesia at risk for potentially lethal carbon monoxide (CO) poisoning due to the degradation of volatile inhaled anesthetics by such dry absorbents.

Knolle et al.  found that by placing a layer of Amsorb either above or below a conventional CO2absorbent, depending on the direction of gas flow, a color change in the Amsorb can be used to detect the desiccation of the conventional absorbent. This could alert a clinician to change the conventional CO2absorbent to prevent CO formation when volatile inhaled anesthetics are employed.

However, the authors note that Amsorb itself has been shown to be an effective CO2absorbent, which does not produce CO when used with volatile inhaled anesthetics even when completely dry. 2,3Therefore, patients face no risk of CO poisoning when Amsorb alone is employed as the CO2absorbent.

My question to the authors is: why not simply use Amsorb alone as the CO2absorbent and avoid the risk of CO production at all? This would also avoid the need to specially prepare a conventional strong base containing CO2absorbent with a layer of Amsorb in the appropriate area and watch for a color change there.

Knolle E, Linert W, Gilly H: Using Amsorb to detect dehydration of CO2absorbents containing strong base. A nesthesiology 2002; 97: 454–9
Murray J, Renfrew C, Bedi A, McCrystral C, Jones D, Fee P: Amsorb, a new carbon dioxide absorbent for use in anesthetic breathing systems. A nesthesiology 1999; 92: 1342–8
Knolle E, Heinze G, Gilly H: Small carbon monoxide formation in absorbents does not correlate with small carbon dioxide absorption. Anesth Analg 2002; 95: 650–5