Compound A does not accumulate during closed circuit sevoflurane anaesthesia with the Physioflex

Area of Science:

• Anesthesiology
• Chemical Engineering
• Toxicology

Background:

• Sevoflurane is a widely used inhalation anesthetic.
• Closed-circuit anesthesia systems can potentially lead to the accumulation of volatile anesthetic degradation products.
• Soda lime is a common absorbent used in anesthesia circuits.

Purpose of the Study:

• To investigate the accumulation of sevoflurane degradation products, specifically Compound A, in a closed circle anesthesia system (Physioflex).
• To assess the safety of sevoflurane use in prolonged (>2 hours) abdominal surgeries.
• To determine if degradation products exceed toxicological thresholds.

Main Methods:

• Gas composition analysis of inspiratory and end-tidal gases during sevoflurane anesthesia in five adult patients undergoing abdominal surgery.
• Continuous gas flow (70 L/min) and a closed circle system with fresh soda lime were employed.
• Measurements were taken from the tracheal tube and inspiratory limb at various time points.

Main Results:

• Inspiratory Compound A (3-8 ppm) was detected after 10 minutes but did not accumulate over 2 hours.
• Expired Compound A concentrations were lower (1.5-3 ppm), indicating patient absorption.
• Compound A levels were significantly below the nephrotoxicity threshold in rats (by >20-fold).
• Other degradation products like Compound B and methanol were not detected.

Conclusions:

• Sevoflurane degradation products, including Compound A, did not accumulate to significant levels in the Physioflex closed circle system.
• Observed Compound A concentrations were well below established nephrotoxic thresholds.
• The study suggests sevoflurane can be used safely in closed-circuit anesthesia with soda lime for prolonged procedures.