[Arterial hypertension in the hemodialysis patient. A model of salt-sensitive hypertension in man]

Abstract

In uremic patient treated by hemodialysis (HD), a low potassium intake and a salt load due to diet and or a high sodium concentration in dialysate are often associated to refractory hypertension. Numerous reports in general population, based on epidemiologic and demographic data, have pointed to the relationship between sodium intake and hypertension. The degree of blood pressure fall in patients who have evidence of salt-sensitivity varies directly with the severity of the hypertension, being most prominent in those with higher pressures. Recent studies have suggested that a reduction of dialysate 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 mmol/L in combination with an attempt to lower salt intake by advising the patients to eat a NaCl-restricted diet of no more than 6-8 g/day. During the period under study, dialysis time was kept constant. A significant increase of ultrafiltrate sodium concentration was observed during the first week after 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 +/- 13 mmHg) without a change 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 decrease in peripheral resistance. A link between sympathetic overactivity as it is found in haemodialysis patients and sodium load could be a stimulating hypothesis. It is concluded that increasing dialysate sodium in short dialysis is responsible for the high prevalence of arterial hypertension often insufficiently controlled by antihypertensive medication. In hemodialysis patients with refractory hypertension, the lowering of the dialysate sodium concentration is indicated.