Soda lime

Its purpose is to eliminate carbon dioxide (CO2) from breathing gases, preventing carbon dioxide retention and, eventually, carbon dioxide poisoning. The creation of soda lime involves treating slaked lime with a concentrated sodium hydroxide solution. The primary components of soda lime include: calcium oxide (CaO) constituting approximately 75%, water (H2O) accounting for around 20%, sodium hydroxide (NaOH) making up about 3%, and potassium hydroxide (KOH) present at approximately 0.1%. During general anesthesia, a patient's exhaled gases, containing carbon dioxide, pass through an anaesthesia machine's breathing circuit, containing a soda lime canister filled with soda lime granules. Medical-grade soda lime includes an indicating dye that changes color when it reaches its carbon dioxide absorption capacity. To ensure proper functioning, a carbon dioxide scrubber (or soda lime canister) should not be used if the indicating dye is activated. Standard anesthesia machines typically contain up to 2 kilograms (4.4 lb) of soda lime granules. Recent carbon dioxide absorbents have been developed to minimize the risk of toxic by-product formation resulting from the interaction between the absorbent and inhaled anesthetics, like halothane.