PERFORMANCE OF ERRONEOUSLY FILLED SEVOFLURANE, ENFLURANE AND OTHER AGENT-SPECIFIC VAPORIZERS

Objective. Erroneous filling of an agent-specific anesthesia vaporizer may result in concentration and potency outputs that are very differe nt from those expected from the concentration dial setting. Enflurane and sevoflurane have relatively similar saturated vapor pressures (SVP s 175 mmHg and 160 mmHg, respectively, at 20 degrees C) and potencies (MACs 1.68% and 2%, respectively). We derived an equation to relate th e vapor concentration output of an agent-specific vaporizer to the gas inflow splitting ratio (SR) created by the vaporizer and the SVP of t he potent inhaled agent. Methods. To test the validity of this equatio n, we filled an Enfluratec 4 enflurane vaporizer with sevoflurane and a Penlon PPV Sigma sevoflurane vaporizer with enflurane and compared t he vapor concentration outputs with our predictions. Results. The equa tion accurately predicted the vapor concentration outputs of the erron eously filled enflurane and sevoflurane vaporizers. The potency (MAC) output of the erroneously filled Enfluratec 4 vaporizer decreased by 2 2%-33%, and that of the Penlon PPV Sigma sevoflurane vaporizer increas ed by 21%-31% from those expected from the concentration dial settings . Conclusion. When an agent-specific variable bypass vaporizer is erro neously filled, the vapor concentration outputs can be predicted from the splitting ratio created by setting the vaporizer concentration dia l and the SVP of the agent.