• B R Tiffany, W A Berk, I K Todd, and S R White.
• Department of Emergency Medicine, Detroit Receiving Hospital and University Health Center, St. Antoine.
• Chest. 1993 Sep 1;104(3):831-4.

HypothesisIntravenous magnesium sulfate improves objective measures of expiratory flow in patients with acute severe exacerbations of asthma.DesignRandomized, double-blind, placebo-controlled trial.SettingUrban emergency department.ParticipantsForty-eight asthmatic patients aged 18 to 60 years with initial peak expiratory flow rate (PEFR) < 200 L/min who failed to double their initial PEFR after two standardized albuterol treatments.InterventionsSubjects were randomized to three groups: a loading dose of magnesium sulfate, 2 g IV over 20 min followed by 2 g/h over 4 h (infusion), magnesium sulfate, 2 g over 20 min followed by placebo infusion (bolus), or placebo loading dose and infusion (placebo). All subjects received standardized aminophylline and steroid therapy.MeasurementsThe PEFR and FEV1 were measured at the start of the loading dose, and 20, 50, 80, 140, 200, and 260 min later using a water-displacement spirometer. Changes from baseline were compared by one-way analysis of variance for repeated measures.ResultsMagnesium sulfate administration did not at any time significantly improve either FEV1 (F = 0.036, p = 0.96) or PEFR (F = 0.51, p = 0.61). This study had the power to detect a PEFR difference of 26 L/min and a FEV1 difference of 0.19 L between groups (beta = 0.20, alpha = 0.05 two-tailed significance).ConclusionUse of IV magnesium sulfate in addition to standard therapy does not provide clinically meaningful improvement of objective measures of expiratory flow in patients with moderate to severe asthma exacerbations.

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