Subanesthetic sevoflurane does not affect sympathetic or parasympathetic function.

To evaluate the effects of subanesthetic enflurane and sevoflurane on the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS), the blood level of norepinephrine (NE) and fluctuations in the R-R intervals were measured on electrocardiogram in humans given either 0.5 MAC enflurane or sevoflurane. Enflurane suppressed circulating plasma NE and elevated coefficients of variation (CV) of R-R intervals after 20 and 30 min of inhalation. In contrast, 0.5 MAC of sevoflurane slightly stimulated cardiovascular function without any change in blood NE. Sevoflurane lowered the CV to 84% of control after 30 min of inhalation. These results indicate that subanesthetic concentrations of sevoflurane are unlikely to perturb sympathetic and parasympathetic activities in humans without surgical stimulation when compared with enflurane.