Dialysate magnesium level and blood pressure

We investigated the way dialysate magnesium (dMg) concentrations could affect blood pressure (BP) during hemodialysis (HD).

Eight HD patients underwent four midweek HD treatments consecutively, using, during each four-hour HD session, one of the following four dialysate formulations, in randomized order, which differed only with regard to dMg and dialysate calcium (dCa) concentrations (in mmol/L): 0.75 dMg, 1.75 dCa (group I); 0.25 dMg, 1.75 dCa (group II); 0.75 dMg, 1.25 dCa (group III); 0.25 dMg, 1.25 dCa (group IV). Before HD and at four 60-minute intervals during the HD sessions, BP and noninvasive measurements of cardiac index (CI) were obtained. Additionally, 14 HD patients were treated for four weeks with 0.5 mmol/L dMg, followed by four weeks with 0.25 mmol/L dMg, and another four weeks with 0.75 mmol/L dMg, in random order. In all treatments dCa was 1.25 mmol/L. BP and symptoms were recorded during each HD session.

Mean arterial pressure (MAP) decreased to a significantly (P < 0.05) greater extent in group IV compared to the other groups. This substantial drop in MAP by 15.2% in group IV, paralleled by a 12.1% and 17% drop in CI and stroke index, respectively, was not seen in group II, despite comparable reductions in intradialytic serum Mg (sMg) of about 35% in both groups. In groups I and III, the increase in sMg by 2% did not compromise BP via vasodilatation. In the second study, treatment with 0.75 mmol/L dMg was superior to the other two treatments regarding intradialytic morbidity (P < 0.001) and BP stability (P < 0.05).

We (1) identified a dialysis solution containing 0.25 mmol/L Mg and 1.25 mmol/L Ca as a major cause of intradialytic hypotension (IDH) due to an impairment of myocardial contractility, and (2) showed that increasing dMg level to 0.75 mmol/L could prevent IDH frequently seen with the use of 1.25 mmol/L dCa. Thus, manipulating dMg levels independently or in concert with dCa levels might have important implications with regard to dialysis tolerance.