Salt sensitivity of blood pressure in patients with primary hypertension

Objective measures of blood pressure (BP) sensitivity to 72-h salt depletion were evaluated. Salt sensitivity is defined as a measurable decrease of diastolic BP (DBP) after depletion. Changes in office auscultatory and oscillometric DBP were compared with oscillometric ambulatory DBP. In 35 women and men with mild hypertension, 24-h ambulatory DBP; sodium, potassium, albumin, and creatinine in 24-h urine; serum-creatinine; and body weight were measured before and at the end of the salt-free period. The oscillometric method detected larger and more uniform decreases in DBP compared to the auscultatory method. The salt depletion-induced changes in auscultatory DBP but not in ambulatory DBP were positively related to its baseline level. The salt sensitivity was positively related to the age and negatively related to the number of hypertensive symptoms. It was not related to body mass index and body weight decrease after salt depletion. The changes in ambulatory DBP were correlated to changes in office DBP (r = 0.46 for the auscultatory method; r = 0.58 for the oscillometric method). In only half the cases, the direction and size of pressure changes were reflected similarly in all three methods. Although the correlation between the methods points to the biological soundness of the salt sensitivity concept, the individual classification is prone to variation.