Fludrocortisone's Test in Salt Sensitivity

• Blood pressure difference [ Time Frame: Baseline and 11 weeks ] [ Designated as safety issue: Yes ]
  Patient will be analised for salt sensitivity in two phases: during the cycle of diets (low and high salt), lasting two weeks, and during administration of fludrocortisone (0.4 mg/day for 7 days). In the begin and finish of each phase (diets and fludrocortisone), blood pressure will be measure by oscilometric methods in the office and by ambulatory blood pressure monitoring (ABPM) and home blood pressure monitoring (HBPM) out-of-office. The difference of blood pressure between each phase will be used to classify the patient in salt sensitive or salt resistant.
  
  

The relationship between excessive salt intake and hypertension is well established in the literature. However, the intensity of blood pressure increase in response to such intake varies among individuals. The salt sensitivity is, therefore, measurement of blood pressure response to the variation of salt content in the diet in each individual. The importance of sensitivity to salt has been well demonstrated, with higher mortality in both hypertensive patients and in normotensives subjects. Despite this importance, the methods of assessment salt sensitivity are difficult to be adopted into clinical practice. The test considered the standard for sensitivity to salt is the administration of two cycles of low and high sodium diets, and checked the change in mean arterial pressure between the end of the first and second cycles. Note, therefore, that the supply of diets, as well as patient compliance, are difficult in routine clinical practice. The aim of this study is to compare the administration of fludrocortisone in identifying patients with salt sensitive with the gold standard low and high sodium diets. A experimental cross-over study, with 40 uncomplicated hypertensive patients, will be conducted. Initially, all patients are going to stay in a period of washout of antihypertensive medications with a duration of four weeks, receiving placebo. Following this, they will be submitted for salt sensitivity in two phases: during the cycle of diets, lasting two weeks, and during administration of fludrocortisone in a dose of 0.4 mg/day for 7 days. Between these two phases will be a period of four weeks. The order of the phases will be divided by simple randomization. Moreover, we will evaluate the relationship between blood pressure and 24-hour urinary sodium excretion during cycles of diet low / high sodium. After the study, the test accuracy of fludrocortisone will be analyzed by calculating the sensitivity, specificity and positive predictive value and negative, in addition to the construction of a ROC curve for determining a cutoff point to improve the specificity and sensitivity of the test.