Asthma in adults (acute): magnesium sulfate treatment
Asthma is a common and heterogeneous chronic condition affecting 1 in 12 adults in the UK, characterised by variability in clinical symptoms and airflow obstruction. Sudden severe exacerbations or acute attacks of asthma may be unpredictable and life threatening; many occur in patients with severe asthma, but patients with mild disease are also at risk. Acute asthma often develops slowly over several hours, meaning that there is often sufficient time for therapeutic intervention to prevent hospital admissions. Despite this, there were 54,300 emergency hospital admissions for acute asthma in the UK in the 12 months to May 2014.
Focus of the review
There has been a lack of recent studies of the treatment of adults with acute severe asthma, with the exception of those evaluating the effects of magnesium sulfate. Magnesium sulfate is an airway smooth muscle relaxant that has been used as a bronchodilator in patients with acute asthma in conjunction with standard therapy. Its safety and efficacy have not previously been confirmed, and its use has been considered controversial.
Comments on evidence
Interpretation of the studies of inhaled and intravenous magnesium sulfate in acute asthma in adults is hindered by wide variations in study methods. Particularly important are the differences in treatments given to control populations, which reflect variation in standard treatment guidelines between different healthcare settings. The use of systemic corticosteroids, nebulised beta2 agonists, and additional nebulised ipratropium is widely considered by clinicians to provide optimum treatment; and we have evaluated the evidence for magnesium as an additional treatment rather than an alternative bronchodilator. Some studies have suggested that magnesium treatment, particularly via the intravenous route, has a particular benefit in patients who present with severe features but, again, interpretation of the data here is difficult due to inconsistencies in the definition and categorisation of severity. Given the heterogeneous nature of asthma, this is an important caveat. Furthermore, many studies exclude patients with life-threatening asthma, making it difficult to generalise the findings to this patient population. This is problematic because, outside of clinical trials, it is often those patients presenting with life-threatening features who are considered for magnesium therapy when standard treatment regimens fail to control the disease. Additional limitations in the available evidence relate to differences in the dose, route, and precise method of administration of magnesium; and it remains possible that alternative dose regimens may have different effects. An important aim of treatment is to prevent hospital admissions, but consideration of this outcome variable between different trials is also problematic because hospital admission rates are likely to be dependent on several factors, including the organisation of healthcare, delays in presentation, psychosocial factors, and the availability and quality of community care. The findings of this overview are confined to acute asthma in adults; there appears to be a differential benefit from intravenous magnesium in children, and paediatric studies are not considered in this evaluation.
Search and appraisal summary
The update literature search for this overview was carried out from the date of the last search, April 2010, to November 2014. For more information on the electronic databases searched and criteria applied during assessment of studies for potential relevance to the overview, please see the Methods section. Searching of electronic databases retrieved 50 studies. After deduplication and removal of conference abstracts, 24 records were screened for inclusion in the overview. Appraisal of titles and abstracts led to the exclusion of 10 studies and the further review of 14 full publications. Of the 14 full articles evaluated, one systematic review was updated and one systematic review was added at this update.
Substantive changes at this update
Magnesium sulfate (iv) versus placebo One systematic review added. Categorisation changed from 'unknown effectiveness' to 'likely to be beneficial'.
Magnesium sulfate (nebulised) plus short-acting beta2 agonists (inhaled) versus short-acting beta2 agonists (inhaled) alone One systematic review updated. Categorisation unchanged (unknown effectiveness).
INTRODUCTION: About 10% of adults have suffered an attack of asthma, and up to 5% of these have severe disease that responds poorly to treatment. Patients with severe disease have an increased risk of death, but patients with mild to moderate disease are also at risk of exacerbations. Most guidelines about the management of asthma follow stepwise protocols. This overview does not endorse or follow any particular protocol, but presents the evidence about a specific intervention, magnesium sulfate. METHODS AND OUTCOMES: We conducted a systematic overview, aiming to answer the following clinical question: What are the effects of magnesium sulfate for acute asthma? We searched: Medline, Embase, The Cochrane Library, and other important databases up to November 2014 (BMJ Clinical Evidence overviews are updated periodically; please check our website for the most up-to-date version of this overview). RESULTS: At this update, searching of electronic databases retrieved 50 studies. After deduplication and removal of conference abstracts, 24 records were screened for inclusion in the overview. Appraisal of titles and abstracts led to the exclusion of 10 studies and the further review of 14 full publications. Of the 14 full articles evaluated, one systematic review was updated and one systematic review was added at this update. We performed a GRADE evaluation for five PICO combinations. CONCLUSIONS: In this systematic overview, we categorised the efficacy for two comparisons based on information about the effectiveness and safety of magnesium sulfate (iv) versus placebo and magnesium sulfate (nebulised) plus short-acting beta2 agonists (inhaled) versus short-acting beta2 agonists (inhaled) alone.
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Exhaled nitric oxide levels to guide treatment for adults with asthma. ( 10 January 2017 )
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