Ionized magnesium levels and the ratio of ionized calcium to magnesium in asthma patients before and after treatment with magnesium

Objective. Prior studies have been equivocal about the efficacy of magnesium therapy in acute asthma exacerbations. We hypothesize that pretreatment ionized magnesium (Mg²⁺) levels and/or the ratio of ionized calcium to ionized magnesium (Ca²⁺/Mg²⁺) may have been confounding variables in these previous studies. Here, we report on the incidence of abnormal divalent ion levels in our asthma population. Material and methods. The study was designed as a randomized, double-blind, placebo-controlled trial of intravenous magnesium. Inclusion criteria were: age >18 years, percentage predicted forced expiratory volume (FEV₁) <75 % after an initial beta-agonist. African-American patients (AA) at an urban university hospital were randomized to 2 g IV Mg or placebo. Mg ²⁺ and Ca²⁺/Mg²⁺ levels were measured pre- and post-infusion. Data were reported as means±SD. Student's t-test and Fisher's exact test were used where appropriate (α=0.05, two tailed) Results. Fifty-five AA patients (mean age of 42.7 years±15.6 years, range18-75 years) were studied. A significantly (p<0.05) lower level of Mg²⁺ was found in asthma (AS) patients compared with that in the AA group, by 0.03 mmol/L (95 % CI, 0.007-0.053 mmol/L). The AS group had a mean increase in Ca²⁺/Mg²⁺ ratios over the AA group, of 0.27 (95 % CI, 0.16-0.38); 100 % of patients with abnormal divalent ion levels were corrected with IV magnesium. Conclusions. We identified a subgroup of asthmatic patients with significant abnormalities in their divalent ion concentrations, which was corrected with IV magnesium.