Magnesium Sulfate in Asthma

MonkeyArrow · Jun 22, 2016

Can someone explain the physiology/pharmacology behind why mag sulfate is indicated as a rescue treatment for severe acute asthma? I have read it has bronchodilatory and anti-inflammatory effects but I have never heard of it being used outside of the cardiac context.

Carlos Danger · Jun 22, 2016

Is is a direct smooth muscle relaxant. Same mechanism by which it is an effective tocolytic.

Carlos Danger · Jun 22, 2016

Also an effective analgesic adjunct.

TrueNorthMedic · Jun 22, 2016

I believe it inhibits Ca+ from entering the cell. This causes the smooth muscle relaxant effect. We're getting mag sulfate added to our protocols soon. I've heard it works well.

DesertMedic66 · Jun 22, 2016

I was finally granted orders for it on my last asthma patient. RR in the high 40s and EtCO2 in the 15mmHg range.

CPAP, albuterol, Atrovent, Mag drip (2gms over 10 mins). Upon arrival at the hospital the patients RR was in the high 20 range and EtCO2 was in the 30mmHg range.

Carlos Danger · Jun 22, 2016

Research actually shows it doesn't help much in refractory asthma.

Still worth trying though, IMO.

SeeNoMore · Jun 25, 2016

I know more Paramedics than I can count who swear by this intervention. In fact, you know the call was serious when "I got the order for Mag!". They know for sure it helped. Just ask them. Many of these patients did not receive Epi (IM or otherwise) despite apparently being on death's doorstep. It's all well and good to incorporate new interventions, but you should not automatically prioritize them for no good reason.

NPO · Jun 25, 2016

Remi said:
Research actually shows it doesn't help much in refractory asthma.

Still worth trying though, IMO.

We use it quite frequently, and to great success.

We're 'supposed to' get orders for it, but most medics don't, and use a clause in our protocols that allows us to forego base contact if calling the hospital will delay an immediately needed intervention.

We even have an employee with known severe asthma. We run on her a few times per year. The only thing that works is mag, and on her it's a first line treatment.

Carlos Danger · Jun 25, 2016

NPO said:
We use it quite frequently, and to great success.

We're 'supposed to' get orders for it, but most medics don't, and use a clause in our protocols that allows us to forego base contact if calling the hospital will delay an immediately needed intervention.

We even have an employee with known severe asthma. We run on her a few times per year. The only thing that works is mag, and on her it's a first line treatment.

I know a lot of people swear by mag.

I'm not saying it doesn't work or that it doesn't have its place, but my understanding is that it is not strongly supported by the literature as compared to other interventions.

I use it liberally in the OR as an analgesic adjunct. As long as the renal function is good there is little risk.

Brandon O · Jun 25, 2016

Remi said:
I use it liberally in the OR as an analgesic adjunct.

News to me. Can you elaborate?

StCEMT · Jul 7, 2016

I was talking to a student in another program yesterday who said he has used it a few times and it workes really well. I havent used it personally, but I have heard good things about it from others.

Nova1300 · Jul 9, 2016

Brandon O said:
News to me. Can you elaborate?

There are a handful of relatively well-done, although small, trials looking at post-op opiate consumption in patients given magnesium as a supplemental analgesic. There is a consistent trend among several of those trials toward a decrease use in opiates and better pain scores with magnesium. The current thought on mechanism is an augmentation of the NMDA receptor.

I see little harm and perhaps a good deal of benefit to administration of magnesium in either case. Although the jury is still out in reactive airway disease, I do think it has some efficacy in analgesia. Hypermagnesemia is uncommon outside of the OB suite where large amounts are given as infusions for tocolysis. While renal failure may decrease clearance of excess magnesium, I have never seen it get to dangerous levels. It takes a LOT of magnesium to become toxic.

What we see relatively consistently in the ICU is hypomagnesemia. There seems to be a brisk washout of magnesium in patients administered crystaloid. I'm not sure if it's ever been studied, but anecdotally most of my patients will have laboratory evidence of hypomagnesemia post op and many require consistent supplementation during critical illness.

So I think in most cases the risk-benefit ratio of magnesium administration favors giving it while the jury is still deliberating.

Brandon O · Jul 9, 2016

Interesting stuff, thanks! I wonder if this could be extrapolated to mean that giving mag to an ICU patient under continual sedation may (mysteriously) increase their level of somnolence.

Nova1300 · Jul 10, 2016

Brandon O said:
Interesting stuff, thanks! I wonder if this could be extrapolated to mean that giving mag to an ICU patient under continual sedation may (mysteriously) increase their level of somnolence.

I'm sure if you got the serum levels high enough, you would see somnolence and decreased reflexes, as you do when patients in OB get toxic. However, HYPOmagnesemia can cause a profound muscular weakness and in turn cause failure to liberate from the ventilator and look like oversedation. So really, it can go either way. You just have to be aware of the symptpms at both ends of the spectrum.

The other clinical symptoms of hypomagnesemia are somewhat similar to those of hypocalcemia... chovstek sign, tetany, spasms, etc. and hypomagnesemia and hypocalcemia frequently co-exist. Same goes for K+. It's easy to miss if you're not looking.

Carlos Danger · Jul 12, 2016

Brandon O said:
Interesting stuff, thanks! I wonder if this could be extrapolated to mean that giving mag to an ICU patient under continual sedation may (mysteriously) increase their level of somnolence.

I don't doubt that it could mean that. Anecdotally, I've been using it pretty routinely for maybe my past 15 "big" cases ("big" being relative, of course) and it seems to roughly double the effectiveness of whatever narcotic I use. Today it was a 52 kg patient having a total lap hysterectomy. She was asleep for about 2.5 hours and in that time I gave her a total of 1.4mg of hydromorphone and 3g of mag. I gave 1mg of dilaudid right after induction, and some ketamine a couple min before incision. Then I gave the rest of the dilaudid about halfway through the case, and the mag was given in multiple small boluses spread fairly evenly throughout the case. No local from the surgeon. She woke up looking like she'd had at least 3mg of hydromorphone (actually woke more slowly than I would have liked), and PACU didn't have to give her anything else until her PO med shortly before she was discharged.

I'm not sure how that translates to ICU sedation - never mind the EMS setting - but there may be some application there.

P.S. It causes a very (IME, anyway) noticeable potentiation of neuromuscular blockade, as well.

CentralCalEMT · Jul 12, 2016

Mag (2 Grams a 250 bag of saline run in over 10 minutes) is a standing order here for severe asthma that does not respond to Albuterol, Epi, CPAP, etc. What I have noticed is either the mag works as a wonder drug when nothing else works, or it has absolutely no effect on the patient. I have seen patients in severe distress on death's doorstep go from one word dyspnea to speaking in complete sentences by the time we got to the hospital a couple of times. However, I have had multiple occasions where the patient did not improve at all with the mag drip. I have never seen it cause hypotension which they tell us to watch for. I wonder if there are certain factors/certain populations that research has not yet identified yet that immensely benefit from mag; while for the rest, it does nothing. I do know paramedics that swear by mag. But for me, it has only worked in a few instances.

Alan L Serve · Jul 13, 2016

Epi before Mag.

bakertaylor28 · Feb 1, 2017

CentralCalEMT said:
Mag (2 Grams a 250 bag of saline run in over 10 minutes) is a standing order here for severe asthma that does not respond to Albuterol, Epi, CPAP, etc. What I have noticed is either the mag works as a wonder drug when nothing else works, or it has absolutely no effect on the patient. I have seen patients in severe distress on death's doorstep go from one word dyspnea to speaking in complete sentences by the time we got to the hospital a couple of times. However, I have had multiple occasions where the patient did not improve at all with the mag drip. I have never seen it cause hypotension which they tell us to watch for. I wonder if there are certain factors/certain populations that research has not yet identified yet that immensely benefit from mag; while for the rest, it does nothing. I do know paramedics that swear by mag. But for me, it has only worked in a few instances.

It works and all in terms of the theory of muscle relaxant properties, but for the fact that Magnesium Sulfate is a mild acid ( pH of approximately 5.5 - 6.5 ) Hence, it would stand that since elevated CO2 tends to cause respiratory acidosis, we wouldn't want to be making things more acidic. (Think the reasons we use Sodium Bicarbonate in cardiac arrest cases.)

NomadicMedic · Feb 1, 2017

bakertaylor28 said:
It works and all in terms of the theory of muscle relaxant properties, but for the fact that Magnesium Sulfate is a mild acid ( pH of approximately 5.5 - 6.5 ) Hence, it would stand that since elevated CO2 tends to cause respiratory acidosis, we wouldn't want to be making things more acidic. (Think the reasons we use Sodium Bicarbonate in cardiac arrest cases.)

Again, where do you come from?

You post some of the most inane content I've ever seen.

bakertaylor28 · Feb 1, 2017

DEmedic said:
Again, where do you come from?

You post some of the most inane content I've ever seen.

And you have major issues if you didn't see it coming. Look it up. The general rule of basic underlying thought process is to avoid further acidifying a hypercapnic patient. (Remember that thing about CO2 being an acid?) Of course its a rather old school thought process....that let me guess they don't teach anymore??? And I'm willing to bet that an asthmatic is probably going to be significantly hypercapnic by the time they call us up. Just a hunch. So, Gee, Barbie, why don't you get your panties out of a wad, apply your lipstick to the right side of your face, and get on with yourself. Because FRANKLY I don't have time for what ever personal agenda you have going on. [Slam door in face HERE]

Magnesium Sulfate in Asthma

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