Low-sodium haemodialysis without fluid removal improves blood pressure control in chronic haemodialysis patients

Hypertension is an important and well-established risk factor for both cardiovascular and cerebrovascular disease. Hypertension is much more common in patients on renal replacement therapy than in the general population. Up to 80% of patients on renal replacement therapy are hypertensive and about 50% of dialysis patients die from cardiovascular causes. Salt and water overload are major factors exacerbating hypertension in the dialysis population. This was a prospective crossover study of 10 patients examining the effect of haemodialysis for 2 weeks using usual (Na+ 138-140 mmol/L) sodium dialysate with a 2-week period of low (reduced by an average of 5 mmol/L Na+ to 133 mmol/L on average) sodium dialysate on inter-dialytic ambulatory blood pressure (ABPM) and trans-thoracic bioimpedance (TTB). Ten patients, mean age 67 years, completed the study (two women and eight men). No patient became severely hyponatraemic during the study period. Mean 48 h inter-dialytic blood pressure (BP) fell from 141/83 to 133/78 (P < 0.01). Mean arterial BP measured immediately prior to TTB fell from 92.8 mmHg to 87.5 mmHg (P < 0.01) during the low-sodium haemodialysis period. Afterload (systemic vascular resistive index - SVRI) measured by TTB fell significantly during the low-sodium haemodialysis period (SVRI on Na+-140 = 3426 cf. Na+-134 = 2281; P = 0.01). Dialysate sodium reduction without extra fluid removal had a beneficial effect on inter-dialytic 48-h blood pressure in chronic stable haemodialysis patients. Lowering dialysate sodium reduced the systemic vascular resistance index as measured by TTB. Reduction of dialysate sodium was well tolerated, although mild dizzines and cramps did occur. These data suggest that sodium overload and water overload may have independent effects on BP and that simple-to-achieve and modest changes in dialysate sodium could usefully augment the action of antihypertensives in dialysis patients.