Albuterol and Systemic impact

[PepperRN]

Not sure which forum to post in, so I'll try here, and move me if you need to!

Question about Albuterol or other SABAs:

If IV route is used for asthma unresponsive to inhaler or neb, would the B2 receptors in the skeletal muscles around the body also dilate? If so, how does that then reconcile with the vasoconstriction in the heart (due to off-target impact on B1 receptors)....do they fight against each other? Or is the impact irrelevant because the heart just overrules either way?

Does IV or inhaler/neb have a greater impact on the B1s? And presumably with inhaler/neb the systemic affect on the skeletal B2 is negligible - I assume because the metered dose is enough o work on the B2s in the lungs, leaving very little left to be absorbed systemically to have much affect around the body. However, even with the metered dose into the lungs, there is an effect on the heart because it is so intimately tied to the resp system.

I'm just thinking that with the IV route, there may actually be less impact on the B1s in the heart than with the inhaler/neb route. It's therefore possible that the B2s in the skeletal muscles will be effected, as will the B2s in the lungs, and the B1s will be but to a lesser extent, which could potentially lead to hypotension....or is that thinking way off base??

Thanks!

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[Raney Schauer]

IBTL

 

[PepperRN]

In Before the lock or IBTL is used in forum threads to get the admin to close/lock the thread. This is a way to show that the thread is incredibly dumb or goes against the rules of the message board.

Why? It's a genuine question. Dumb to you maybe, but not to me. As I said in my first sentence, please move if necessary.

 

[Raney Schauer]

I know what IBTL stands for, that’s why I wrote it. What you appear to be doing is asking for homework/study/medical advice help, a violation of the standing rule set.

IBTL.

 

[GoSpursGo]

We actually have decided that we're only going to lock overt hw help threads like "here are my chemistry problems" and "find me references for my research paper." General discussion of concepts is fine.

However, a Cochrane review showed that IV albuterol doesn't have evidence to support its use in asthma, and isn't available in the US anyways. Possibly because you get such a widespread and unfocused effect. If asthma isn't responsive to inhaled albuterol we'll typically use something else.

 

[libertyyne]

We actually have decided that we're only going to lock overt hw help threads like "here are my chemistry problems" and "find me references for my research paper." General discussion of concepts is fine.

However, a Cochrane review showed that IV albuterol doesn't have evidence to support its use in asthma, and isn't available in the US anyways. Possibly because you get such a widespread and unfocused effect. If asthma isn't responsive to inhaled albuterol we'll typically use something else.

Thanks. This is awesome. Probably will lead to more science discussions on the forum.

 

[PepperRN]

Thank you for the responses.

This was absolutely not a homework question. I am actually a student nurse, but I wasn't getting anywhere in my nursing forum as nobody knew the answer. I don't actually need to know this stuff to this depth (that's why we have you guys!) but it was for my own interest...it helps me understand the human response/side effects if I can connect the dots, so to speak.

 

[libertyyne]

Thank you for the responses.

This was absolutely not a homework question. I am actually a student nurse, but I wasn't getting anywhere in my nursing forum as nobody knew the answer. I don't actually need to know this stuff to this depth (that's why we have you guys!) but it was for my own interest...it helps me understand the human response/side effects if I can connect the dots, so to speak.

Another thing that you havent touched upon is distribution of B1 vs B2 and specificity for B1 vs B2 of the drug.

 

[Psai]

My understanding is that albuterol is relatively b2 specific. It can also affect other b2 receptors outside of the bronchodilating effects. Tachycardia is a very common side effect. As was mentioned above, we don't use iv albuterol but we do terbutaline, especially IM for pregnant patients to delay prelabor. You can definitely see a drop in blood pressure and a significant increase in heart rate with terbutaline. I've seen a patient's heart rate jump 50 bpm with a single dose.

 

[PepperRN]

Distribution B1 = heart, B2 = lungs and skeletal muscles.
Drug Specificity = that was my original question; but I'll change it since a poster above has said that IV SABAs are not used.

So - with an inhaled SABA (let's say Albuterol), presumably the B2 receptors across the body are not impacted because 1. It is a measured dose of med - enough to "connect" with the B2 receptors in the lungs, leaving very little left to react systemically and 2. The route is very specific to its target.

From what I have read, the B1 receptors in the heart react to the SABA, but to a much lesser degree. Therefore you do get an increased heart rate, but generally this won't be too much of a concern unless we've given more that the recommended dose. So - can I conclude for that that the B1 receptors respond to the SABA as they would to a catecholamine, but in a much milder way.

 

[PepperRN]

My understanding is that albuterol is relatively b2 specific. It can also affect other b2 receptors outside of the bronchodilating effects. Tachycardia is a very common side effect. As was mentioned above, we don't use iv albuterol but we do terbutaline, especially IM for pregnant patients to delay prelabor. You can definitely see a drop in blood pressure and a significant increase in heart rate with terbutaline. I've seen a patient's heart rate jump 50 bpm with a single dose.

Thank you!!! Why is terbutaline ok to use but not Albuterol in IV - is it not as potent?

So I think from what you are saying, with the IV use of a SABA, the B2 receptors around the body (in the skeletal muscles) are affected, hence will dilate, and hence there IS a drop in blood pressure. With the inhaled version, it is much more confined to the lungs so the impact is negligible on the B2s around the body - so we see an increase in BP from the response of the heart's B1s.

Is that what you're saying?

 

[libertyyne]

Thank you!!! Why is terbutaline ok to use but not Albuterol in IV - is it not as potent?

So I think from what you are saying, with the IV use of a SABA, the B2 receptors around the body (in the skeletal muscles) are affected, hence will dilate, and hence there IS a drop in blood pressure. With the inhaled version, it is much more confined to the lungs so the impact is negligible on the B2s around the body - so we see an increase in BP from the response of the heart's B1s.

Is that what you're saying?

The response in the heart may be do to the minimal b1 activation or more reflexive in nature due to the massive amount of vasodilation.

 

[PepperRN]

The response in the heart may be do to the minimal b1 activation or more reflexive in nature due to the massive amount of vasodilation.

Oh of course! The vasodilation in the lungs could trigger increased BP....good point.

So when the med is used in IV (terbutaline as mentioned above), and the B2s across the body all vasodilate, the DROP in BP is because it is too much for the heart to compensate for?

p.s. I don't know why I'm getting obsessed with this, LOL! We only need to know the basics: when SABAs are used v LABA/LAMA and their side effects.

 

[Psai]

Oh of course! The vasodilation in the lungs could trigger increased BP....good point.

So when the med is used in IV (terbutaline as mentioned above), and the B2s across the body all vasodilate, the DROP in BP is because it is too much for the heart to compensate for?

p.s. I don't know why I'm getting obsessed with this, LOL! We only need to know the basics: when SABAs are used v LABA/LAMA and their side effects.

Maybe think about PepperMD or PepperPhD

 

[PepperRN]

Maybe think about PepperMD or PepperPhD

LOL! Cute!

No - I'm happy to leave most of this with you guys

 

[libertyyne]

Oh of course! The vasodilation in the lungs could trigger increased BP....good point.

So when the med is used in IV (terbutaline as mentioned above), and the B2s across the body all vasodilate, the DROP in BP is because it is too much for the heart to compensate for?

p.s. I don't know why I'm getting obsessed with this, LOL! We only need to know the basics: when SABAs are used v LABA/LAMA and their side effects.

inhalation= more local effects due to smaller doses, and direct delivery to the lungs=> less systematic effects.
Injection= presumably larger dose =>vasodilation of peripheral smooth muscle=>reduced peripheral resistance=>Reduced BP=>reflexive Tachy

 

[PepperRN]

Thank you libertyyne

 

[evilbooyaa]

I am a big fan of threads like this, and I really hope that we can have more interactions like this on this forum, like I remember it a few years ago.