Experiences with the new inhalational agents in low-flow anesthesia and closed-circuit technique. Monitoring and technical equipment.

Abstract

During recent years interest has focused on two completely fluorinated ethers, desflurane and sevoflurane, which promise a shorter induction of and emergence from anesthesia. Their physicochemical properties differ from isoflurane, enflurane and halothane, thus requiring new technical equipment and leading to a change in anesthesiological procedures. Low-flow anesthesia with desflurane can be performed, the technical equipment is available, especially vaporizers and gas analyzers. In contrast to anesthesia with isoflurane, enflurane and halothane, the initial high-flow wash-in period with desflurane can be shorter and the vaporizer setting can remain unchanged after fresh gas flow reduction. In order to administer desflurane and sevoflurane in closed circuit technique, new technical equipment is needed. Therefore, a computer controlled anesthesia machine was modified and the feedback mechanism to maintain the end-tidal anesthetic concentration was simulated. Isoflurane, desflurane or sevoflurane needed the same time for wash-in. Wash-out was slower with isoflurane; however, the technical equipment should be adapted to increase the elimination of the new agents. The consumption of desflurane and sevoflurane is effectively reduced by low-flow and closed circuit anesthesia.