Hypertension in hemodialysis patients: a human model of salt sensitivity of blood pressure?

In uremic patient treated by hemodialysis (HD), a law potassium intake and a salt load due to diet and or a high sodium concentration in dialysat are often associated to refractory hypertension. Numerous reports in general po pulation, based on epidemioologic and demographic data, have pointed to the relationship between sodium intake and hypertension. The degree of blood p ressure fall in patients who have evidence of salt-sensitivity varies direc tly with the severity of the hypertension, being most prominent in those wi th higher pressures. Recent studies have suggested that a reduction of dial ysate sodium can control hypertension in maintenance haemodialysis patients . In this study, five hypertensive haemodialysis patients were assigned to a regime of lowering the dialysate sodium concentration from 142 to 135 mmo l/L in combination with an attempt to lower salt intake by advising the pat ients to eat a NaCl-restricted diet of no more than 6-8 g/day. During the p eriod under study, dialysis time was kept constant. A significant increase of ultrafiltrate sodium concentration was observed during the first week af ter lowering the dialysate sodium concentration. Post dialysis systolic and diastolic pressures showed a clear trend to fall (systolic pressure 174+/- 18 vs 118+/-13 mmHg, diastolic pressure 96+/-7 vs 75+/-3 mmHg) without a ch ange of dry weight. The reduction of the mean arterial pressure on 48 h was demonstrated with ambulatory blood pressure recording. The results of this study suggest that reducing the dialysate sodium concentration lead to a d ecrease in peripheral resistance. A link between sympathetic overactivity a s it is found in haemodialysis patients and sodium load could be a stimulat ing hypothesis. It is concluded that increasing dialysate sodium in short dialysis is respo nsible for the high prevalence of arterial hypertension often insufficientl y controlled by antihypertensive medication. In hemodialysis patients with refractory hypertension, the lowering of the dialysate sodium concentration is indicated.