Accuracy of calculated volatile agent consumption from fresh gas content

Area of Science:

• Anesthesiology
• Pharmacoeconomics

Background:

• Accurate volatile anesthetic (VA) consumption measurement is crucial for agent-sparing strategies and billing.
• Weighing vaporizers is the gold standard but often impractical.
• Calculating VA consumption from fresh gas flow (FGF) and VA data offers a viable alternative.

Purpose of the Study:

• To evaluate the accuracy of calculating volatile anesthetic consumption using fresh gas composition compared to the gold standard of vaporizer weight difference.
• To assess the reliability of a formula-based method for determining sevoflurane and desflurane usage.

Main Methods:

• A prospective laboratory study compared formula-based VA consumption calculations with measured vaporizer weight differences.
• Ten sevoflurane and ten desflurane anesthesia cases were analyzed.
• Average differences and data spread between calculated and measured values were assessed.

Main Results:

• Calculated sevoflurane consumption showed a slight overestimation of 3.0 ± 2.9 ml (6.2%) compared to measured values.
• Calculated desflurane consumption also overestimated measured values by 3.5 ± 6.7 ml (5.0%).
• All calculated values fell within ±1.96 standard deviations of the measured values for both agents.

Conclusions:

• Formula-based calculation of volatile anesthetic consumption for sevoflurane and desflurane is sufficiently accurate for estimating economic impact.
• This calculation method allows for both retrospective analysis of anesthesia records and prospective use.
• The findings support the use of calculated VA consumption as a practical alternative to direct vaporizer weighing.