SPECTRAL-ANALYSIS OF HEMODYNAMICS DURING INFUSIONS OF EPINEPHRINE ANDNOREPINEPHRINE IN MEN

Spectral analysis of fluctuations in heart rate (HR) and arterial bloo d pressure (BP) during a 6-h infusion of epinephrine (15 ng.kg(-1).min (-1)) or norepinephrine (30 ng.kg(-1).min(-1)) in 10 normotensive male s was used to analyze effects of peripheral sympathetic nervous system activity and adrenal medullary discharge on cardiovascular variabilit y. Power spectra were calculated for each 5-min period for HR, systoli c BP, and diastolic BP to yield power values for three frequency bands : low (0.02-0.06 Hz), mid (0.07-0.14 Hz), and high (0.15-0.40 Hz). Inf usion of epinephrine and norepinephrine induced plasma concentrations of epinephrine and norepinephrine, respectively, within the high physi ological range. Spectral analysis showed that low-frequency fluctuatio ns of BP during infusions of epinephrine and midfrequency fluctuations of BP during infusion of norepinephrine changed in opposite direction s. These fluctuations may represent different components of short-term cardiovascular control mechanisms during situations that mimic increa sed sympathoadrenal activity. No changes were observed in HR fluctuati ons or high-frequency fluctuations of BP after either catecholamine. O ur data imply that changes in concentrations of circulating catecholam ines cannot be unequivocally labeled as indexes of an altered sympatho adrenal involvement in short-term cardiovascular control.