Does a reduction in dialysate sodium improve blood pressure control in haemodialysis patients?

Introduction: There has been debate as to the value of lower sodium dialysates to control blood pressure in haemodialysis patients, as sodium is predominantly removed by ultrafiltration. Methods: Re-audit of clinical practice following reduction in dialysate sodium concentration. Results: Overall dialysate sodium concentration decreased from 138.9 +/- 1.7 to 137.8 +/- 1.7 mmol/L (mean +/- standard deviation), resulting in a reduction in pre- and post-dialysis mean arterial pressure (MAP) of 4 mmHg (from 100.6 +/- 15.6 to 97.1 +/- 15.6, P < 0.01 and from 91.7 +/- 15.6 to 87.1 +/- 14.6, P < 0.001 respectively), yet fewer patients were prescribed antihypertensives (49.6 vs 60.6%), and less antihypertensive medications/patient (mean 0.86 vs 1.05), ultrafiltration requirements (2.8% vs 3.2% body weight, P < 0.001), and symptomatic intradialytic hypotension (0.19 vs 0.28 episodes per week, P < 0.001). A multivariable model showed that for a dialysate sodium of 136 mmol/L, younger patients had higher MAP than older patients (0.35 mmHg lower MAP/year older; but with a dialysate sodium of 140 mmol/L, there was minimal association of MAP with age (0.07 mmHg higher MAP/year older). Conclusion: Change in clinical practice, amounting to a modest reduction in dialysate sodium was associated with a reduction not only in pre- and post-dialysis blood pressures, but also ultrafiltration requirements and symptomatic intradialytic hypotension. However, this effect on blood pressure was most marked for older patients and women, within minimal effects for younger patients, and lesser effects for men, suggesting that dialysate sodium reduction alone may help improve blood pressure control, but requires additional factors such as dietary sodium restriction to be effective in younger male patients.