This is a roller coaster journey for me. Many years ago Virchester ED was one of the first hospitals to start using Magnesium for the treatment of acute severe asthma. This prompted great concern amongst some in-hospital colleagues….., and when we started using it in kids OMG (as my daughter might say) it felt as though we were trying to kill the kids!
Time goes on.
These days the first question out of the admitting teams mouths is “Have you given Magnesium yet?” and I’ve even seen MgSO4 administered to mild/moderate asthmatics in preference to Salbutamol for patients who don’t like nebulisers. I sigh and take the opportunity for learning delivery (that’s me to them…..).
Anyway, the evidence for Magnesium in asthma was never really that fantastic. Systematic reviews showed an effect but it was not quite as dramatic as some people now think. There is a nice review here in theEMJ from the Sheffield team, which informed the latest RCT pre-published in the Lancet this month.
The 3MG trial led by Steve Goodacre in Sheffield aimed to determine if nebulised Mg and IV Mg are effective in the management of acute severe asthma.
[learn_more caption=”Who was studied?”] The authors wanted to look at acute severe asthma. In this study that meant adult patients with acute asthma, with either a peak expiratory flow rate of <50% of best or predicted, respiratory rate >25 breaths per min, heart rate >110 beats per min, or inability to complete sentences in one breath. Interestingly they excluded patients with life threatening features, interesting as that’s a group that give me great anxiety. Arguably the life threatening patients are the ones where I tend to chuck the kitchen sink of therapies at (Ed – bit more technical than that I’m sure, but I know what you mean).
There were three groups in the study. All patients got an IV and a nebuliser, but the groups received.
- IV MgSO4 and placebo neb
- IV placebo and MgSO4 neb
- IV placebo and placebo neb
So, a pretty good design with a placebo arm. I like this as the evidence was on the weak side from past trials and systematic reviews.
Principal outcomes were admission to hospital and breathlessness at 2 hours.
[/learn_more] [learn_more caption=”The main results”] Interesting. Read the full paper, but in essence the effect of MgSO4 in these patients appears minimal. Nebulised MgSO4 appears to have no effect at all. IV has a minimal effect on admission rates, but does not affect the patient centred outcome of breathlessness.
They also look at a bunch of other outcomes, complications, side effects and again the benefit of MgSO4 is absent in nebulised and minimal for IV. This is a very different picture to the perception of colleagues in my practice and I think this will come as a shock.
[/learn_more] [learn_more caption=”Any concerns with methodology?”] Not especially. This is a good pragmatic trial. Care in all groups was performed at the discretion of the treating teams according to British Thoracic Society guidelines, and arguably that might vary, but I like this. Pragmatic trials probably indicate the difference that we will get in practice and are a bit more ‘real world’ than some highly controlled studies. This is a good paper for teaching about such trials (I’m keeping it on my list of good trials for critical appraisal)[/learn_more] [learn_more caption=”What do the results mean for me and my clinical practice?”] Well, the rollercoaster plummets again. Is MgSO4 down and out? Well probably…
- Nebulised MgSO4 is almost certainly not worth it in adults.
- Nebulised MgSO4 works in kids (the MAGNETIC trial results)
- We don’t know about patients with life threatening asthma – I’ll probably still keep giving it.
- I am going to have some interesting conversations with the admitting teams over the next few months. Perhaps in a few years their first statement will be….‘You haven’t given Magnesium have you????’
What about you?
- Are you going to stop using IV Magnesium on the basis of this?
- Are you going to stop using Nebulised Magnesium in adults?
- What about patients with life threatening features?
I’d love to hear your thoughts.[/learn_more]
Conflict of interest – I know & respect all the authors. I don’t think it colours my judgement, but just so you know 🙂