Magnesium for Severe Asthma


I love fireworks! It is fun to say “Ooh and Ah!” while pontificating the amazing chemical reactions that are being displayed (ok, it is a little Geeky, but true). Magnesium is quite brilliant when ignited.

Interestingly, the use of magnesium for your severe asthma patient may actually prevent a chaotic firework display in your pediatric ED (ie, needing to intubate that patient).

Much appreciation to Dr. Emily MacNeill for reinforcing this topic during a fantastic intellectual conversation (also known as conference) yesterday!

Magnesium for Severe Asthma

  • Debate often surrounds the utility of magnesium for the patient with an acute asthma exacerbation.
    • I recall being told when I was a resident, “you either believe it works or you don’t.”
      • Now, that is my kind of medicine… ambiguous.
    • Admittedly, studies are not overwhelmingly positive.
  • In 2007, a meta-analysis (yes, I know it is not a double-blinded placebo control trial) did conclude that IV magnesium had a significantly positive effect on respiratory function and hospital admissions… for patients with SEVERE ASTHMA exacerbation.
  • Cochrane Database found similar results when reviewing the available literature: “In the severe subgroup, admissions were reduced in those receiving magnesium sulfate (odds ratio: 0.10, 95% confidence interval: 0.04 to 0.27).
  • Importantly, no clinically significant adverse events were reported.


  • We all know that patients with severe asthma may require intubation, but that the goal is to prevent that from happening.
    • About 1/4 of kids intubated for asthma have complications (pneumothorax, impaired Preload, cardiovascular collapse) because of increased intrathoracic pressures.
    • Mechanical ventilation for asthma is associated with increased risk of death.
  • Bonus Morsel: If the patient that you just intubated for his/her asthma becomes unstable / hypotensive, the first thing you should do is disconnect the ventilator and allow the patient to exhale (likely that intrathoracic pressures have increased preventing venous return to the right heart). Consider pneumothorax after that.

  • If the child doesn’t need to be intubated upon initial evaluation in my ED, then I should strive to avoid it by any means necessary.
  • This is where the Kitchen Sink comes into play.
    • Beta Agonists (naturally)
    • Inhaled anticholingerics (useful in that first hour of therapy).
    • IV steroids (because it is hard to take PO meds when you are struggling to breath)
    • Magnesium sulfate
    • Heliox (see Morsel)
    • BiPap

Magnesium belongs in The Kitchen Sink

  • So that data of it’s absolute efficacy may be debatable… but we all agree intubating the patient is suboptimal… and Magnesium is relatively safe to give.
  • Given that there is evidence to support its use in the severe exacerbation, my humble opinion is that we should use it sooner rather than later in those patients to help prevent further decline of our patient’s respiratory status.
    • If the patient looks terrible – give it up front with the rest of the kitchen sink ready to be initiated.
    • If the patient doesn’t improve as you would like and you are considering continuous nebulized beta-agonists – use it.



Mohammed S, Goodacre S. Intravenous and nebulised magnesium sulphate for acute asthma: systematic review and meta-analysis. Emerg Med J. 2007 Dec; 24(12): 823-30.

Canadian Paediatric Society. Position Statement: Managing the paediatric patient with an acute asthma exacerbation. May 1, 2012.

Rowe BH, Bretzlaff J, Bourdon C, Bota G, Blitz S, Camargo CA. Magnesium sulfate for treating exacerbations of acute asthma in the emergency department. Cochrane Database of Systematic Reviews 2000, Issue 1. Art. No.: CD001490. DOI: 10.1002/14651858.CD001490.


Sean M. Fox
Sean M. Fox
Articles: 583


  1. […] for the Morsels.  We have discussed my preference for MDIs over Nebs as well as the utility of Magnesium.  In addition, we have covered mechanical ventilation for asthma and how Delayed Sequence […]

  2. Regarding the “kitchen sink” approach, what about IM epi? I work at a community hospital and I have given a dose of IM epi to severe asthmatics during that period of chaos that frequently coincides with the arrival of a critically ill child to the department. While nurses are trying to find appropriately sized pediatric equipment, start an IV, and respiratory is being paged, I can slip in a dose of epi quickly and without any need for pt cooperation.



    • Mike,
      Excellent addition to the “Kitchen Sink” of critical asthma management!
      IM Epi certainly can be used effectively in a pinch.
      Let’s keep it on the list of potentially helpful tools!
      Thank you,

  3. There are other drugs that we give despite the lack of double blinded evidence that they work: albuterol in a bronchiolitic child is a good example. We all give it right after the child arrives with the hope that it will work. And it does sometimes. I believe that there are subgroups of kids where it works and some subgroups where it does not. Since the risk of giving it is small…we just give it.
    Same rational can apply to Mg

  4. And of course it’s really interesting to see how MgSO4 appears to be less beneficial in the adult population in the recent 3MG trial. This caused a bit of controversy in adult medicine particularly as the 3MG excluded patients with life threatening signs.

    Also worth mentioning the Magnetic trial which we participated in looking at nebulised MgSO4 in kids.

    The key questions remain about really sick kids and adults. The current approach appears to be give everything you can….!

    • Well stated, sir!
      I always aim for doing what is reasonable. Magnesium’s risk : benefit ratio favors giving it a try, particularly when weighed against the risk : benefit of intubation. If the child is going to be getting an IV, then Mag will be ordered concurrently from me. I actually apply the same rationale to adults… maybe not as well supported, but then again a lot of what we do is more art than science.

      Thank you for your astute insight!

  5. Any thoughts about the idea that ionized magnesium is the biologically active form, not total magnesium. There is some literature to support the idea patients with low levels of ionized magnesium are the “responders” to magnesium, and those with normal levels of ionized magnesium don’t respond. There may be racial predilections to levels of ionized magnesium as well.

    • Chris,
      I think that it makes some intuitive sense, but I am not sure that I would ever be able to get a ionized Mag level back in a timely fashion for me to use that theory clinically. Again, I think that we should be using Mag earlier in the course of the presentation of the severe asthma exacerbation. In the end, hopefully we will see more research to answer this more definitively (although, there isn’t much money in the Magnesium market).
      Hope that you are doing well!

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