Can I Have My Cake and Eat It Too?

The less soluble, newer inhaled anesthetics desflurane and sevoflurane offer a more rapid recovery from anesthesia than more soluble older agents, such as isoflurane. However, this rapid recovery comes at a price: The new anesthetics are more expensive. Is it possible to have the best of both worlds by using isoflurane for most of anesthesia, reserving desflurane (or sevoflurane) for the final minutes? Could such an approach provide the economy of isoflurane and the rapid recovery of desflurane? Neumann and colleagues^[93] tested this premise. Volunteers were anesthetized for 2 hours on three occasions: once with 1.25 MAC of isoflurane; once with 1.25 MAC of desflurane; and once with 1.5 hours of 1.25 MAC of isoflurane, followed by 0.5 hour of a combination of desflurane and isoflurane (i.e., crossover approach). The combination provided a total of 1.25 MAC (i.e., desflurane was added as the isoflurane was eliminated, with the addition being sufficient to sustain a total of 1.25 MAC). To ensure economy, all anesthetics were delivered at a 2 L/min inflow rate.

Contrary to the premise, recovery after the crossover was no faster than recovery after isoflurane alone ( Fig. 5-22 ).

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Figure 5-22 Volunteers were anesthetized for 2 hours on three occasions: once with 1.25 minimum alveolar concentration (MAC) of isoflurane; once with 1.25 MAC of desflurane; and once with 1.5 hours of 1.25 MAC isoflurane, followed by 0.5 hour of a combination of desflurane and isoflurane (i.e., crossover administration). The combination provided a total of 1.25 MAC (i.e., desflurane was added as the isoflurane was eliminated, with the addition being sufficient to sustain a total of 1.25 MAC). All anesthetics were delivered at a 2-L/min inflow rate. At the end of 2 hours, anesthetic administration was discontinued and a non-rebreathing system applied. The digit symbol substitution test (DSST) was applied at 15-minute intervals, and the results are displayed as a percentage of the control (preanesthesia) results. Recovery of judgment and cognition as defined by the DSST was more rapid at 15, 30, and 45 minutes with desflurane given alone (asterisks indicate significant differences from isoflurane or crossover results). (Data from Neumann MA, Weiskopf RB, Gong DH, et al: Changing from isoflurane to desflurane towards the end of anesthesia does not accelerate recovery in humans. Anesthesiology 88:914–921, 1998.)