Hemodynamic effects of nicotinic acid infusion in normotensive and hypertensive subjects

Nicotonic acid (NA) infusions are associated with peripheral vasodilation from the generation of vascular prostaglandins with minimal effects on blood pressure (BP) in normotensive subjects. We studied the effects of a NA infusion in 10 hypertensive and 11 normotensive individuals to further characterize systemic hemodynamic responses to NA using pulse waveform analysis. Blood pressure, stroke volume, cardiac output, total peripheral resistance, large and small artery elasticity were determined before and after a 1-h NA infusion. In the normotensives, systolic, diastolic, mean BP, and pulse pressure were not affected by NA. In contrast, the hypertensive subjects experienced a decrease in mean BP from 105 +/- 2 mm Hg to 100 +/- 3 mm Hg (P <.01) accompanied by significant decreases in systolic, diastolic, and pulse pressures. The differential BP response occurred despite comparable increases in heart rate (11% to 13%, P </=.05) and similar decreases in total peripheral resistance (6%, P </=.05) in both groups. However, the normotensive group demonstrated a decrease in overall vascular compliance, measured as stroke volume to pulse pressure ratio, from 2.12 +/- 0.09 to 1.93 +/- 0.09 mL/mm Hg (P <.05). This finding was supported by a decrease in C1 (large artery compliance), assessed by pulse waveform analysis, from 15.8 +/- 1 to 14.2 +/- 1 mL/mm Hg (P <.05). In contrast, overall compliance and C1 were unchanged after the NA infusion in the hypertensive group. These results suggest that there is a differential hemodynamic response to NA infusion in normotensive and hypertensive individuals. The adjustment in vascular compliance may be an important factor in determining overall BP response to NA.