Bronchodilating Effect of Intravenous Magnesium Sulfate in Acute Severe Bronchial Asthma: METHODS
All patients presenting to the emergency department of our hospital with acute severe asthma received standard treatment: 2.5 mg ( = 0.5 ml) albuterol in 4.5 ml saline solution delivered by a powered nebulizer every 4 h; methylprednisolone, 40 mg given intravenously every 12 h; ampicillin, 4 g daily intravenously, or doxycycline, 200 mg orally if signs of infection were present; intravenous aminophylline, 720 to 960 mg daily, adjusted in order to achieve serum theophylline levels between 10 and 20 jig/ml; supplemental oxygen, when necessary, delivered by nasal prongs.
Patients were then admitted to the study protocol after informed consent was received and when meeting the following criteria: a previous diagnosis of bronchial asthma (atopic or nonatopic), with spirometry confirming reversible bronchoconstriction (FEV, below 75 percent predicted, FEV,/FVC less than 60 percent, and an FEV, increase of 15 percent or more after beta^agonist administration) and the present diagnosis of acute, severe asthma, defined by clinical examination and by a FEV, of less than 40 percent predicted.
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Exclusion criteria were: heart failure, pneumonia, life-threatening conditions or neoplastic disorders, acidemia or hypercapnia, and patients who required mechanical ventilation.
Six patients entered the study (aged 45 to 60 years); 12 studies were performed as follows: the first morning after admission, early albuterol administration was suspended under close medical supervision. All other medications were given as before. At 8 am, the best result of three successive blows into a Vitalograph spirometer (Vitalograph Ltd., Buckingham, England) was used to measure baseline FEV,. Infusion of MgS04 was then started for 20 min at 0.615 mmol/min. Spirometry was repeated at the end of the MgS04 infusion and again 30 min later. The latter FEV, values were considered as baseline data for the evaluation of the effect of albuterol inhalation (2.5 mg in 4.5 ml saline by a powered nebulizer in 20 min), which was started immediately after the third session of blows. Finally, spirometry was again performed at the end of the albuterol inhalation.
Throughout the MgS04 infusion and the albuterol inhalation period, blood pressure, heart rate, auscultatory phenomena, subjective findings and adverse effects were closely monitored. Venous blood was sampled just before and at the end of the MgS04 infusion, to measure serum Mg concentration (dry chemistry method, Kodak Ektachem) and red blood cell Mg content (FAAS method). The same procedure was repeated the next day.
Statistical analysis was performed with an IBM PC XT computer running a SPSS/PC + statistics program (SPSS Inc, Chicago).
The Wilcoxon paired test at a significance level of p<0.05 was used when appropriate.