ORTHOSTATIC AND POSTPRANDIAL BLOOD-PRESSURE REDUCTION IN PATIENTS WITH ESSENTIAL-HYPERTENSION

1. The role of the sympathetic nervous system in orthostatic and postprandial blood pressure reduction in patients with essential hypertension was studied in 13 hypertensive patients and 10 age-matched normotensive subjects. 2. The blood pressure (BP), pulse rate, and plasma norepinephrine (NE) were measured: (i) every minute for 20 min in the upright position after overnight recumbency (ii) every 30 min after food intake for 3 h in the supine position. 3. Orthostatic BP reduction (> 13 mmHg in mean BP) was observed in eight hypertensive patients with a maximum after 4 min. Seven of these patients showed postprandial hypotension (> 13 mmHg) with a maximum 90 min after eating, while none of the normotensives exhibited such BP reductions. Before and during the tests the plasma NE levels were higher in hypertensive patients than in the normotensives. The plasma NE level was increased from 370 +/- 80 to 790 +/- 110 pg/mL 4 min after standing (P < 0.01) in hypertensive patients and from 220 +/- 40 to 530 +/- 90 pg/mL (P < 0.01) in normotensive subjects. The plasma NE level was decreased 90 min after food intake from 390 +/- 90 to 260 +/- 80 pg/mL in hypertensives. Changes in plasma NE correlated with those in mean BP after standing for 4 min (r = 0.379, P < 0.05) and also with those 90 min after food intake (r = 0.457, P < 0.05). 4. These findings suggest that patients with essential hypertension have abnormally increased basal sympathetic nerve activity at rest, and that their orthostatic and postprandial BP reductions may both be caused by impairment of the sympathetic nervous system and of cardiovascular reflexes.