Systemic and regional hemodynamics in low, normal and high cardiac output borderline hypertension.

SUMMARY Forty-one patients with borderline hypertension were subdivided into groups with low, normal, and high cardiac index. Cardiac output, intra-arterial pressure, renal blood flow, splanchnic blood flow, plasma volume, red cell mass and plasma renin activity were determined concomitantly, and derived hemodynamic indices were calculated. Cardiac output, arterial pressure and plasma renin activity were also measured after head-up tilt and isometric handgrip. Heart rate and stroke index were significantly higher in patients with normal and high cardiac output than in patients with low cardiac output. A significant difference was also found between the three groups in total blood volume, total peripheral resistance, renal and hepatic blood flow, whereas plasma renin activity and plasma volume did not differ significantly. Cardiac output correlated with plasma (r = 0.500), total blood (r = 0.630) and central blood volumes (r = 0.782). In contrast, a negative correlation was observed between total peripheral resistance, plasma (r = -0.440) and total blood (r =-0.644) volumes. Furthermore, cardiac output, renal (r = 0.550) and hepatic (r = 0.625) blood flows correlated. The response of cardiac output and total peripheral resistance to tilt was more pronounced in high than in low cardiac output borderline hypertension (P < 0.05) whereas handgrip responses were similar in the three groups. We conclude that the fluid volume state is a major determinant of cardiac output and/or peripheral resistance in borderline hypertension with renal and hepatic blood flow varying in parallel. The magnitude of cardiac output, renal and hepatic blood flow depends mainly on the shift of the circulating blood volume to the central circulation.