Fig. 1. Effects of epinephrine, esmolol, nitroprusside, and norepinephrine on PEP (top), low-frequency systolic blood pressure variability (LF-BPV) (middle), and low-frequency heart rate variability (LF-HRV) (bottom) as compared with placebo. Nitroprusside increased LF-BPV and LF-HRV, whereas norepinephrine decreased LF-BPV and LF-HRV. Neither epinephrine nor esmolol had any effect on LF-BPV or LF-HRV.