Calcium chloride within carbon dioxide absorbents prevents Compound A production from sevoflurane.

Calcium chloride (CaCl2)-containing carbon dioxide (CO2) absorbers are characterized by their ability to produce almost no pentafluoroisopropenyl fluoromethyl ether (Compound A), a potentially nephrotoxic byproduct of sevoflurane, in vitro. However, the precise role of CaCl2 in this process remains unclear. We aimed to clarify the role of CaCl2 in vitro and determine whether CaCl2-containing CO2 absorbents produce Compound A during prolonged surgery under low- and minimal-flow sevoflurane anesthesia using Japanese brand Yabashi Lime-f (YL-f). In vitro, a reaction between 1 L of sevoflurane gas (8%) with 5% CO2 and an absorbent specimen (20 g) with or without water was performed in an artificial closed-circuit system for 15 or 60 min at 45 °C. In vivo, patients scheduled for colorectal resection received 2.0 vol% sevoflurane at fresh gas flows of 2.0, 1.0, or 0.5 L/min (N = 6) with YL-f. Gas samples from the anesthetic circuit were collected 6 h after induction and at the conclusion of surgeries lasting over 7 h. Compound A concentrations were measured using gas chromatography-flame ionization detection. Compound A production was observed in CaCl2-free absorbents but not in those containing CaCl2 in vitro. During 60-min reactions, CaCl2-free YL-f derivatives produced a median 3.5 ppm of Compound A, with higher concentrations (7.1 ppm) observed upon the addition of 3 mL of water. YL-f did not produce Compound A, regardless of the presence of water. Compound A was not detected in in vivo samples. In conclusion, CaCl2 suppresses Compound A production from sevoflurane, likely by trapping water within the anesthetic circuit.