RENAL HEMODYNAMIC-EFFECTS OF VASODILATION WITH NIFEDIPINE AND HYDRALAZINE IN PATIENTS WITH HEART-FAILURE

The central and renal hemodynamic effects of nifedipine were evaluated in 9 patients with severe chronic congestive heart failure. Oral nifedipine (34 .+-. 22 mg, mean .+-. standard deviation) was associated with a decrease in systemic vascular resistance from 1748 .+-. 436 to 1321 .+-. 302 dynes .cntdot. s .cntdot. cm-5 (P < 0.001) and mean arterial blood pressure from 96 .+-. to 87 .+-. 6 mm Hg (P < 0.05) and with an increase in cardiac output from 4.2 .+-. 1.1 to 4.9 .+-. 1.2 l/min (P < 0.001). Although renal vascular resistance decreased from 11,988 .+-. 2256 to 10,286 .+-. 3011 dynes .cntdot. s .cntdot. cm-5 (P < 0.05), no significant change was seen in renal blood flow (599 .+-. 120 to 640 .+-. 162 ml/min), glomerular filtration rate (62 .+-. 18 to 62 .+-. 17 ml/min), filtration fraction (18 .+-. 5 to 17 .+-. 6%), the ratio of renal/systemic vascular resistance (7.0 .+-. 1.0 to 7.9 .+-. 1.8) and the ratio of renal blood flow/cardiac output (0.15 .+-. 0.02 to 0.13 .+-. 0.03). I.v. hydralazine (10 .+-. 5 mg), given to 8 of the patients in a randomized crossover design, resulted in a larger increase in cardiac output than did nifedipine (38 .+-. 7 vs. 19 .+-. 10%, P < 0.001) and in an increase in total renal blood flow from 570 .+-. 152 to 645 .+-. 174 ml/min (P < 0.001). Renal vascular resistance decreased from 12,080 .+-. 2934 to 10,153 .+-. 2372 dynes .cntdot. s .cntdot. cm-5 (P < 0.001). The ratio renal/systemic vascular resistance increased from 6.9 .+-. 0.9 to 8.5 .+-. 1.3 (P < 0.001), and the ratio of renal blood flow/cardiac output decreased from 0.15 .+-. 0.02 to 0.13 .+-. 0.03 (P < 0.001). In spite of the improvement in renal blood flow, no change was noted in glomerular filtration rate (57 .+-. 18 to 57 .+-. 11 ml/min) or filtration fraction (16 .+-. 3 to 15 .+-. 3%). The strong arteriolar vasodilation of nifedipine involves the renal circulation and decreases abnormally elevated renal vascular resistance. This effect does not lead to an improvement of renal blood flow or glomerular filtration rate. Vasodilation with hydralazine results in significant improvement of renal perfusion, although renal blood flow does not increase proportionately as much as the total cardiac output. Despite improvement in renal perfusion, hydralazine, similar to nifedipine, does not increase glomerular filtration rate.