Figure 1. Individual recordings of integrated nerve activity and hemodynamic responses from two volunteers who received desflurane. (Top) Tracings from a placebo study. (Bottom) Tracings from a subject pretreated with 5.0 micro gram *symbol* kg sup -1 fentanyl. Comparisons at control, 2 min after propofol administration (2 mg *symbol* kg sup -1), and 2 and 4 min after the mask administration of desflurane are displayed. Propofol virtually abolished sympathetic activity. An earlier and greater activation of sympathetic nerve activity with an attenuated hemodynamic response was seen in the fentanyl-treated subject.