Regarding low-flow anaesthesia (LFA) with FGF <1 L/min in a circle absorber system, which statement is MOST accurate about the risk of accumulation of potentially harmful gases?

• A Carbon monoxide (CO) accumulates due to reaction of sevoflurane with wet soda lime; CO accumulation is the primary risk
• B N2O accumulates to toxic levels in LFA circuits within 30 minutes
• C Desflurane produces compound A in dry carbon dioxide absorbent during LFA
• D Compound A (vinyl halide) accumulates from sevoflurane degradation by desiccated/overheated soda lime/Baralyme; risk increases with LFA ✓

Explanation

Compound A is a nephrotoxic vinyl ether compound produced by the degradation of sevoflurane by carbon dioxide absorbents (especially Baralyme and desiccated/overheated soda lime). Its concentration in the breathing circuit increases with low fresh gas flows (because the compound accumulates) and with high temperatures in the absorbent. Desflurane and isoflurane degrade in DRY desiccated soda lime to produce carbon monoxide (CO), not compound A. FDA label requires FGF ≥2 L/min for sevoflurane in the USA (to prevent compound A accumulation), though European guidelines are less restrictive as clinical nephrotoxicity has not been demonstrated in humans at standard concentrations.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.