Diurnal Variation of Blood Pressure in Patients with Salt Sensitive Hypertension.

Variations of blood pressure (BP) and heart rate (HR) were evaluated in patients with essential hypertension (EH) under the conditions of low salt and high salt intake. Fourteen patients with EH were hospitalized and consecutively kept on a daily salt intake of 3 and 20g for 1 week each. Variations in BP were measured at intervals of 15 or 30min using automatic noninvasive BP recorders. Urinary excretion of norepinephrine (UNEV) was also measured serially. The patients whose mean BP was increased more than 10% by salt loading were classified as salt sensitive hypertensives (SS; n=6), while the rest were defined as salt resistant hypertensives (SR; n=8). In SR, averages of both systolic and diastolic blood pressure at night were significantly lower than those during the daytime for both low salt and high salt conditions. UNEV in SR was also decreased significantly at night in both conditions. In SS, however, the nocturnal fall in blood pressure was not significant during salt loading. Furthermore, in SS, UNEV was not decreased significantly during the night in either condition. These results suggest that salt loading in addition to incomplete inhibition of the sympathetic nervous system at night may be involved in the absence of a nocturnal decrease in BP in patients with salt sensitive hypertension. (Hypertens Res 1993; 16: 233-237)