Factors Affecting the Concentration of Compound A Resulting from the Degradation of Sevoflurane by Soda Lime and Baralyme Registered Trademark in a Standard Anesthetic Circuit

Background Sevoflurane anesthesia is usually performed with fresh gas flow rates greater than 2 l/min due to the toxicity of compound A in rats and limited clinical experience with sevoflurane in low-flow systems. However, to reduce costs, it would be useful to identify ways to reduce compound A concentrations in low-flow sevoflurane anesthesia. This goal of this study was to determine if compound A concentrations can be reduced by using soda lime with water added. Methods Low-flow sevoflurane anesthesia (fresh gas flow of 1 l/min) was performed in 37 patients using soda lime with water added (perhydrated soda lime) or standard soda lime as the carbon dioxide (CO2) absorbent. The soda lime was not changed between patients, but rather was used until CO2 rebreathing occurred. The perhydrated soda lime was prepared by spraying 100 ml distilled water onto 1 kg fresh soda lime, and water was added only when a new bag of soda lime was placed into the canister. Compound A concentrations in the circle system, soda lime temperatures, inspired and end-tidal CO2 and end-tidal sevoflurane concentrations, and CO2 elimination by the patient were measured during anesthesia. Results Compound A concentrations were significantly lower for the perhydrated soda lime (1.9 +/- 1.8 ppm; means +/- SD) than for the standard soda lime (13.9 +/- 8.2 ppm). No differences were seen between the two types of soda lime with regard to the temperature of the soda lime, end-tidal sevoflurane concentrations, or CO2 elimination. Compound A concentration decreased with the total time of soda lime use for both types of soda lime. The CO2 absorption capacity was significantly less for perhydrated soda lime than for standard soda lime. Conclusions Compound A concentrations in the circuit can be reduced by using soda lime with water added. The CO2 absorption capacity of the soda lime is reduced by adding water to it, but this should not be clinically significant.

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The Anesthesia Machine: Managing Exhaled and Waste Gases

10.2310/anes.18281 ◽

2019 ◽

Author(s):

Christine Jette

Keyword(s):

Carbon Monoxide ◽

Malignant Hyperthermia ◽

Operating Room ◽

Improve Patient Safety ◽

Soda Lime ◽

Anesthesia Machine ◽

Co2 Absorption ◽

Carbon Dioxide Absorption ◽

Compound A ◽

Anesthetic Gases

Effective and safe CO2 absorption is critical to the anesthesia circle system to prevent rebreathing and hypercapnia. Advances in the original soda lime–based absorbents and their container systems continue to improve patient safety, reducing the risk of compound A and carbon monoxide production, with seemingly little compromise to the efficiency of CO2 absorption capabilities. Scavenging systems and the removal of waste anesthesia gases remain a critical component to anesthesia care, and vigilance to maintain approved systems is a key to operating room staff safety. Advances in anesthesia machine design have resulted in more complicated internal breathing circuits that are increasingly difficult to rid of trace anesthetic gases. This inadvertently led to a necessary change in guidelines on anesthesia machine preparation for patients susceptible to malignant hyperthermia (MH). This review contains 5 figures, 6 tables, and 59 references. Keywords: carbon dioxide absorption, carbon monoxide, CO2 absorption, compound A, malignant hyperthermia machine preparation, operating room safety, scavenging systems, waste anesthesia gases

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