[The effects of intravenous infused magnesium on hemodynamics and renal water-sodium metabolism in patients with essential hypertension].

Mean arterial pressure (MAP), heart rate (HR), urine volume (UV), urinary excretion of sodium (UNaV), endogenous creatinine clearance (Ccr), fractional excretion of sodium (FENa) were measured before and after intravenous infusion of 10% magnesium sulfate (an initial dose: Mg 13.5 mg/m2.BSA/15 min; a maintenance dose: Mg 2.7 mg/m2.BSA/105 min) in 6 normotensive subjects (NT) and 12 mild-to-moderate essential hypertensives (EHT). Following magnesium infusion, serum magnesium concentration (s-Mg) increased and reached the level of about 1.8 times basal value. Significant increases of UV, UNaV and FENa in both NT and EHT, and a similar tendency of Ccr in EHT were observed, while no significant change in MAP nor HR was found in the two groups. The changes in UNaV (delta UNaV) were positively correlated with those in FENa (delta FENa) and a similar tendency was shown between delta UNaV and change in Ccr (delta Ccr) in all subjects. While there was no significant percentage change of s-Mg (% delta s-Mg) nor of Ccr (% delta Ccr), those of UNaV (% delta UNaV) and FENa (% delta FENa) were significantly greater in EHT. It is concluded from these findings that magnesium infusion produces diuresis and the natriuresis which might result from suppression of renal tubular reabsorption of sodium, without any change in systemic hemodynamics in NT and EHT. The pronounced natriuretic response to magnesium in EHT might contribute to the hypotensive mechanism of magnesium loading in EHT.