Fig. 11. Mean arterial pressure (MAP), heart rate (HR), and muscle sympathetic activity (MSA; total activity) in the awake state, after induction of anesthesia with propofol, when patients were intubated, and during maintenance of general anesthesia with nitrous oxide (70% end-tidal), a combination of nitrous oxide and isoflurane (0.3% and 0.6% end-tidal), and equianesthetic isoflurane (1.2% end-tidal) alone. Data are mean ± SD. During anesthesia with nitrous oxide, MSA increases in comparison with propofol anesthesia. Isoflurane decreases MSA in a dose-dependent manner. Equianesthetic doses of isoflurane combined with nitrous oxide decrease MSA to a much lesser extent than when isoflurane was administered alone. Symbols indicate statistical significance (  P < 0.05) for comparisons with the awake control group (*), with 70% nitrous oxide (†), and with 0.6 vol% isoflurane plus 70% vol% nitrous oxide (▵). Derived from and used with permission from Sellgren  et al. 187