Development and performance of a two-step desflurane-O(2)/N(2)O fresh gas flow sequence

Area of Science:

• Anesthesiology
• Pharmacology
• Medical Devices

Background:

• Maintaining precise anesthetic gas concentrations is crucial for patient safety.
• Desflurane requires specific delivery methods due to its properties.
• Optimizing anesthesia delivery unit machine (ADU) protocols can improve efficiency.

Purpose of the Study:

• To evaluate a combined oxygen/nitrous oxide (O2/N2O) fresh gas flow (FGF) and desflurane vaporizer (FD) sequence.
• To determine if this sequence can maintain end-expired desflurane (FAdes) at 4.5% using the ADU.
• To assess the predictability and clinical acceptability of the anesthetic gas concentrations.

Main Methods:

• Prospective randomized clinical study involving 42 patients.
• Patients received general endotracheal anesthesia with controlled mechanical ventilation.
• Interventions involved determining and testing specific O2/N2O FGF and FD sequences.

Main Results:

• A desflurane vaporizer (FD) setting of 6.5% for 15 minutes, followed by 5.5%, closely approximated the target end-expired desflurane (FAdes) of 4.5%.
• Prospective testing showed low median performance errors (-1%) and absolute performance errors (7.1%).
• Minor adjustments in FD or FGF were needed in a few patients to maintain target FAdes.

Conclusions:

• A simplified O2/N2O fresh gas flow (FGF) sequence with one change at 3 minutes (6 to 0.7 L/min) and one desflurane vaporizer (FD) change at 15 minutes (6.5% to 5.5%) effectively maintained anesthetic gas concentrations.
• The described sequence maintained anesthetic gas concentrations within predictable and clinically acceptable limits during the initial 20 minutes of anesthesia.
• This protocol offers a potentially simpler method for delivering desflurane anesthesia with the ADU.