Nitrous oxide increases enflurane concentrations delivered by Ethrane vaporizers

Area of Science:

• Anesthesiology
• Pharmacology

Background:

• Ethrane (enflurane) is a volatile anesthetic agent.
• Nitrous oxide is commonly used as a supplemental anesthetic gas.
• Vaporizer accuracy is critical for safe anesthetic delivery.

Purpose of the Study:

• To quantify the effect of nitrous oxide on enflurane output from Ethrane vaporizers.
• To assess the impact of varying gas flows on this interaction.
• To determine the clinical implications of altered enflurane delivery.

Main Methods:

• Two calibrated Ethrane vaporizers were tested.
• Enflurane concentrations were measured at total gas flows of 3, 5, and 8 L/min.
• Measurements were taken with oxygen alone and with 60% nitrous oxide in oxygen.

Main Results:

• Nitrous oxide increased enflurane concentrations by 20-40% across most dial settings.
• The effect was consistent regardless of total gas flow.
• Enflurane output at the lowest setting (0.25%) was 0.38%, unaffected by nitrous oxide.
• Maximum concentration changes occurred within approximately 5 minutes.

Conclusions:

• Nitrous oxide alters enflurane output from Ethrane vaporizers, potentially leading to anesthetic overdose.
• The lowest dial setting may not reliably deliver low enflurane concentrations.
• Further investigation into the mechanism of increased enflurane output is warranted.