Physiology help... beta blockers and asthma patients

eva123 · Mar 11, 2013

Ok, calm down and try to breath. Think of it this way, beta blockers are blocking part of the sympathetic nervous system actions. In a SNS response there is peripheral vasoconstriction and bronchodilation (peripheral vasoconstriction to supply more blood to vital organs and bronchodilation to run away or fight). So naturally if it is blocked then there is the opposite effect, peripheral vasodilation and bronchoconstriction (more prominent in an asthma pt than in a pt with a healthy airway). When it comes to vasodilation that is actually an alpha blocker, and the bronchoconstriction is the beta blocker.

hodgieRN · Mar 11, 2013

Also, you have to remember that there different beta receptors in the body. You have Beta 1 and Beta 2. Beta 1 is specific to the heart and Beta 2 is specific to the lungs. If I may quote GrnTea's explaination, "You have one heart = Beta 1, and you have two lungs = Beta 2." When you take a BB, it can not only affect the heart, but other body systems as well. Beta-blcokers also block adrenaline. So, one can even take a BB for anxiety or sleeplessness.

Try not to think Beta-blocker = lower B/P, lower HR. You have to think of the medication as a beta-adrenergic blocker and what happens when beta receptors and adrenergic receptors are blocked in the entire body. The heart rate going down or the blood pressure going down are just the effects of the blockade. If you just remember... BB slow down the heart rate, then you are missing a chunk of information. A decreased HR is the "what" in terms of the end effect, but you have to know the "how and why" of those effects happening. For example, you can say Lasix is diuretic, but have to know how it cause diuresis and what specifically happens in the kidney. This is the fun stuff you will learn in Pharm. So, a beta blocker will cause vasodilation, but that is what happens in one area of the body. It can have a completely different effect in another area. And, if you have a specific disease process, a medication can have adverse effects or toxic reactions when something is stimulated or blocked.

Now, there are BB's that are selective to the heart (cardio-selective BB's). But if they are not selective, then you can have a blockade with your beta 2's.

You should have heard the medication Albuterol in clinicals. It's the medication in breathing treatments. If someone is having trouble breathing, you give albuterol and it opens the airways. But remember, we are still missing the middle chunk of info. Albuterol is a Beta 2 adrenergic agonist. It stimulates beta2-adrenergic receptors in the lungs, resulting in relaxation of bronchial smooth muscle. So, what could happen if you gave a this pt a beta-adrenergic blocker? Cool, huh?

The issue with asthma and BB's is broncospasm. The books will say it is contraindicated to give a beta blocker, and then turn around and give a beta agonist for a breathing treatment. However, current studies are starting to say that BB's in asthmatics is supported due to the decreased mortality rate in heart-associated disease processes. For your sake, follow what your book says. BB = bad in asthmatics. Overall, focus in on how and why medications work. If you understand the action of a medication, the physiologic effect will click.

turnforthenurse, MSN, NP · Mar 11, 2013

Also, don't forget that there are selective (cardioselective) beta blockers, as in they are more likely to affect beta1 receptors (the heart) vs. non-selective beta blockers where they affect both beta1 and beta2. Selective beta blockers can become non-selective in larger doses. Just remember "Beta blockers Acting Exclusively At Myocardium":

Betaxolol

Acebutelol

Esmolol

Atenolol

Metoprolol

Non-selective beta blockers are generally avoided in patients with COPD/asthma because they can cause vasoconstriction (due to affecting the beta2 receptors) and worsen those conditions.

itsdebraanne, ASN, RN · Mar 12, 2013

Also, you have to remember that there different beta receptors in the body. You have Beta 1 and Beta 2. Beta 1 is specific to the heart and Beta 2 is specific to the lungs. If I may quote GrnTea's explaination, "You have one heart = Beta 1, and you have two lungs = Beta 2." When you take a BB, it can not only affect the heart, but other body systems as well. Beta-blcokers also block adrenaline. So, one can even take a BB for anxiety or sleeplessness.
Try not to think Beta-blocker = lower B/P, lower HR. You have to think of the medication as a beta-adrenergic blocker and what happens when beta receptors and adrenergic receptors are blocked in the entire body. The heart rate going down or the blood pressure going down are just the effects of the blockade. If you just remember... BB slow down the heart rate, then you are missing a chunk of information. A decreased HR is the "what" in terms of the end effect, but you have to know the "how and why" of those effects happening. For example, you can say Lasix is diuretic, but have to know how it cause diuresis and what specifically happens in the kidney. This is the fun stuff you will learn in Pharm. So, a beta blocker will cause vasodilation, but that is what happens in one area of the body. It can have a completely different effect in another area. And, if you have a specific disease process, a medication can have adverse effects or toxic reactions when something is stimulated or blocked.
Now, there are BB's that are selective to the heart (cardio-selective BB's). But if they are not selective, then you can have a blockade with your beta 2's.
You should have heard the medication Albuterol in clinicals. It's the medication in breathing treatments. If someone is having trouble breathing, you give albuterol and it opens the airways. But remember, we are still missing the middle chunk of info. Albuterol is a Beta 2 adrenergic agonist. It stimulates beta2-adrenergic receptors in the lungs, resulting in relaxation of bronchial smooth muscle. So, what could happen if you gave a this pt a beta-adrenergic blocker? Cool, huh?
The issue with asthma and BB's is broncospasm. The books will say it is contraindicated to give a beta blocker, and then turn around and give a beta agonist for a breathing treatment. However, current studies are starting to say that BB's in asthmatics is supported due to the decreased mortality rate in heart-associated disease processes. For your sake, follow what your book says. BB = bad in asthmatics. Overall, focus in on how and why medications work. If you understand the action of a medication, the physiologic effect will click.

thank you!!

hodgieRN · Mar 12, 2013

No Problem!

claire628 · Mar 3, 2015

Thanks for the explanation I didn't get it at first but now it makes sense! :yes:

RtToRn1983 · Nov 16, 2016

This was the worst explanation.Youre answer is all over the place that even I'm confused.you sound like you really know a lot. So sticking to just heart lungs and also please preface the basics of the beta receptors BC I am so co fused as to why can't give beta blockers to copd but it causes vasodilation in the heart. I thought any time you stimulate the beta receptors you get an action /constriction-now I'm being told otherwise.