High magnesium dialysate does not improve intradialytic hemodynamics or abrogate myocardial stunning.

Abstract

Hemodialysis (HD) induces myocardial stunning and is associated with adverse cardiovascular outcomes. Intradialytic hypotension is a modifiable determinant of myocardial stunning. Magnesium (Mg) is reported to be valuable in maintaining intradialytic blood pressure, which potentially would protect against demand myocardial ischemia. This study aimed to compare high vs. low dialysate Mg effects on intradialytic hemodynamics and HD-induced myocardial stunning. Twenty stable prevalent HD patients entered a randomized cross-over trial of low (0.5 mmol/L) vs. high (1.0 mmol/L) dialysate Mg. Patients were studied after 2 weeks of standard HD with each Mg concentration. Serial echocardiography assessed myocardial stunning, measured by left ventricular regional wall motion abnormalities (RWMAs). Continuous intradialytic hemodynamics were measured noninvasively using thoracic bioimpedance. Median predialysis serum Mg was higher with high dialysate Mg (1.45[1.29-1.55] vs. 1.03[0.98-1.1] mmol/L, P < 0.0001). There was no significant difference in maximum intradialytic reduction in systolic BP. There was no significant difference in stroke volume, total peripheral resistance, and cardiac output. Overall ventricular global longitudinal strain (GLS) (as a sensitive marker of contractile function) was higher before dialysis in high Mg group, but there was no difference in GLS at peak stress. However, we showed a significant correlation between Mg changes and GLS changes, r = -0.47, P = 0.02. There was no difference in mean number of peak stress RWMAs per patient (4.0 ± 2.2 vs. 4.3 ± 2.9, P = 0.5). Ultrafiltration volume, a critical determinant of stunning, was not different between high and low dialysate Mg studies (1.35[0-3.3] vs. 1.5[0-2.8], P = 0.49). Manipulation of magnesium by altering dialysate magnesium concentration does not influence intradialytic hemodynamic response or HD-induced myocardial stunning in the short term. However, decreasing Mg changes appears to decrease GLS changes.