Introduction The purpose of this work was to compare the variability of mean arterial blood pressure and the nocturnal blood pressure dip in patients with sodium-sensitive and sodium-nonsensitive arterial hypertension on a lowsodium and high-sodium diet.
Material and methods The study group comprised 69 hospitalized patients (19 females and 50 males) with essential arterial hypertension grade I (mild) or II (moderate) according to ESH 2003. Three dietary sodium loads: 100-120, 10-20, 220-240 mmol/24 h were applied in succession for seven days each. A 24 h urine collection was done on day 6 and 7 of the low-sodium and high-sodium diets and used to measure urine volume and concentrations of sodium, potassium, and creatinine. On day 7 of the lowsodium and high-sodium diets blood pressure was monitored for 24 h according to the ABPM protocol with Spacelabs 90207 aparat and recalculated to obtain 24 h (24 h MAP), diurnal (DMAP), and nocturnal (NMAP) mean arterial pressures. Variability of mean arterial pressure was assessed by calculating standard deviation (SD) from all data of the 24 h recording. Nocturnal pressure dip was estimated with the nocturnal to diurnal ratio (N/D). Patients were classified as dippers for reductions of at least 10%, otherwise they were labeled non-dippers. Venous blood samples were obtained in the course of each sodium load to determine PRA, aldosterone, sodium, potassium, and creatinine concentrations using routine methods.
Results Patients with sodium-sensitive (SS) hypertension on low-sodium diet demonstrated significantly lower 24 h MAP, DMAP, and NMAP than sodium-resistant patients (SR). These three parameters were significantly elevated on high-sodium diet in SS as compared with SR patients. Ten SS (21.7%) and only one SR (4.3%) were non-dippers on low-sodium diet, the remaining 36 (78.3%) SS and 22 (95.7%) SR were dippers. On high-sodium diet, there were 30 (65.0%) non-dippers among SS and 3 (13.1%) among SR patients, the remaining 16 (35.0%) SS and 20 (86.9%) SR being dippers. The x² test revealed significantly more non-dippers category on high-sodium diet.
Conclusions Our high-sodium diet in sodium-sensitive hypertensive patients induced not only a significant rise in blood pressure, but also increased the 24 h pressure variability and reduced the nocturnal dip. Such changes are known to increase the risk of cardiovascular episodes. The present findings suggest that reduced sodium intake in SS patients may protect against cardiovascular morbidity by reducing arterial blood pressuure and normalizing the 24 h blood pressure rhythm.