OBJECTIVE Mayer wave (~10 s) blood pressure (BP) oscillations may represent rhythmic vasomotor activity. However, it remains unclear if volatile anesthetics disturb the coherence between heart rate (HR) and BP rhythms in this region, which may result in improperly affecting BP-HR modulation by the baroreflex, especially when sympathetic stimulation is evoked during general anesthesia using sevoflurane-nitrous oxide (Sev-N2O). METHODS Twenty-seven patients were anesthetized with Sev-N2O, followed by surgical incision which induces Mayer wave augmentation. Baseline status before surgical incision was compared with that of 19 awake volunteers, and with status after surgical incision. Baroreflex function was assessed by gain and coherence by transfer function analysis, and the baroreflex effectiveness index (BEI). BP Mayer waves were measured by BP variability at a low frequency (LF) of ~0.1 Hz, and spontaneous baroreflex sensitivity (BRS) was obtained by assessing transfer function gain at LF (BRSLF), and the sequence technique (BRSSEQ). RESULTS Sev-N2O anesthesia markedly reduced Mayer waves by 93%, BRSLF by 42%, BRSSEQ by 81%, BEI by 37%, coherence by 42%, and the number of coherent segments by 73%, compared with awake controls. During sympathetic stimulation by surgical incision, however, augmentation of Mayer waves (-1.57±0.72 vs. -0.60±1.00, ln mmHg2 P<0.001) did not improve depressed coherence above 0.5 (0.37±0.09 vs. 0.43±0.11) or BEI (0.17±0.13 vs. 0.13±0.05). CONCLUSIONS Sev-N2O anesthesia alters the link between HR and BP Mayer wave oscillation even during sympathetic stimulation, indicating weak spontaneous baroreceptor-HR modulation during general anesthesia.