Effect of intravenous magnesium sulfate on blood magnesium parameters

Magnesium sulfate was administered intravenously (0.6 mEq/kg body weight over 10 min) to 13 patients with hypertrophic cardiomyopathy undergoing electrophysiologic testing. Total serum, ultrafilterable and protein-bound serum, mononuclear blood cell (MBC) content and concentration, and red blood cell (RBC) concentration of Mg were measured at the following intervals: (1) baseline (before Mg infusion), (2) at the end of infusion, and (3) approximately 40 min after the end of infusion. The total serum, ultrafilterable, and protein-bound fractions rose immediately after infusion and fell by 40 min. The RBC Mg rose and fell less sharply than the serum parameters after Mg infusion. In contrast, the MBC Mg content continued to rise significantly at 40 min after Mg infusion, and MBC concentration showed a continued trend to rise, although this was not statistically significant.