The rationale for this study comparing different types of anesthetic maintenance is based on the amount of systemic metabolic breakdown and the low repartion rates within the various tissues and the very rapid elimination of desflurane in respect to the other common inhalation and intravenous anesthetics as possible factors in the rate of recovery of cognitive function and the appearance of post operative delirium. After general anesthesia with desflurane there is less residual hypnotic agent for elimination in the circulation and tissue with respect to the amount given than with propofol or sevoflurance (1-3).