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ilostthegamespacedx t1_iw6qm44 wrote

The answer is no. “Blood thinner” is somewhat of a misnomer as it does not change the viscosity or concentration of any component of the blood, but prevents the coagulation cascade at some point depending on the agent used. Beta blockers do reduce cardiac output, but not close to any degree that would compromise flow to an organ system like the GI tract. Not to mention that the stomach, although vascular like you mentioned, does not really perform a lot of absorption of nutrients. This occurs mostly in the small intestine where the blood supply is essential to take nutrients to the portal system.

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beyardo t1_iw6wekg wrote

Yeah people don’t realize how much clotting has already been done almost as soon as blood is exposed to open air, so when patients on anticoagulation have a bleed, it definitely looks a lot thinner

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Prehensile t1_iw6zdus wrote

Dumb question, based largely on what is probably an over-simplified understanding of cardiac output. I thought beta blockers improved cardiac output?

I always thought of it more in terms of the contractility improvement than anything, although I know a beta blocker alters other things included in CO, but with that basis of understanding in mind, maybe I'm missing the fact that some other factor outweighs the contractility thing?

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tampering t1_iw71in1 wrote

I think you have it reversed.

Beta receptors are receptors for epinephrine (adrenaline). Activation of the receptors among other effects, increases heart rate and force of contraction, and constricts blood vessels (these raise blood pressure). It can also make you more alert to the point of jitteryness. Beta2 receptors are found in the airway can cause the bronchioles to open improving breathing. So commonly used puffers for asthma etc probably contain the B2 activator.

A B-blocker blocks these responses from happening. So they block increases cardiac output associated with excitement or stress, and keep your heart and breathing at baseline.

And that is why B blockers are banned in precision sports such as snooker or target shooting. B2 Activators such as those asthma puffers are banned in cardio heavy sports because they improve the ability to pull oxygen through the airway.

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Prehensile t1_iw78hmk wrote

Okay, thanks for the clarification; I know it's used in musical performance, so I could've followed that case back to its correct line of explanation if I'd thought about it. And that's really interesting about the precision sports - I wouldn't have thought of the advantage of a beta blocker in sports like that but it makes perfect sense.

For some reason, I could never keep the adrenergic receptors straight. I think part of the difficulty for me, personally, is that I've taken a beta blocker and felt like it was easier to "breathe" which is obviously nonsensical from a bronchiole standpoint, so I probably keep transposing the effect in my head to make sense of that.

Thanks for the chance to revisit some of this!

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IFNy t1_iw72a3w wrote

Beta blockers don't improve cardiac output (in fact they can worsen it in some cases). They block adrenaline receptors: adrenaline makes your heart beat faster and more vigorously, so with this drugs you have the opposite effect (slower heart rate, less powerful contractions). So the cardiac output decreases (or at least doesn't improve despite adrenaline stimulation). Cardiac output in fact depends mainly on: heart rate, blood volume and contraction

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originaljazzman t1_iw73pb6 wrote

Not to be pedantic but if someone is take a beta blocker for atrial fibrillation it will increase cardiac output despite the reduction in heart rate. Actually most people who take a beta blocker probably have an increase in CO due to higher stroke volume. Only for those who take it for sinus tachycardia would have a deceased in CO.

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SomeLettuce8 t1_iw78hwb wrote

CO = EF x HR so what you’re discussing is that they will increase EF with increased end diastolic pressures but decreased HR will ultimately shift the equation to a lower cardiac output

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Shezzanator t1_iw79lq0 wrote

CO = Stroke volume x hr. It's a fine balance. If someone is in af with fvr then stroke volume will be low because of decreased preload (as there won't be as much time for ventricles to fill) therefore slowing hr will allow more filling and increased sv and ultimately co.

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originaljazzman t1_iw7cly4 wrote

No CO = SV x HR. EF = (SV/EDV)/100. Please tell me more about how CHF patients take beta blockers to decrease the CO though /s

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yourname92 t1_iw733sy wrote

If they are used correctly they can improve cardiac output.

When you need to go on beta blockers you can have some problems with your heart not pumping correctly. High BP does not correlate to high cardiac output.

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[deleted] t1_iw7sci9 wrote

[deleted]

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vasavasorum t1_iw7zc9j wrote

Stiff hearts due to cardiac remodelling get improved CO with a reduction in HF due to incresed end-diastolic volumes as described by the Frank-Starling equation.

The simple equation for CO doesn't always hold, especially in pathological physiology. There are many exceptions in clinical medicine.

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Prehensile t1_iw8tn4a wrote

Yeah, where I went wrong in particular was in misremembering the relationship with contractility. I thought a beta blocker was a positive inotrope, not a negative one. But I also have pretty atrocious memory and recall, so I figured I was missing something, somewhere.

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backroundagain t1_iw7vxxx wrote

That being said, one does run a higher risk of a GI bleed while on anticoagulants based on various risk factors.

Beta blockers work a bit too systemically to cause a specific issue in the gut, though nadolol does have a niche in treating portal hypertension.

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BioSigh t1_iw853fq wrote

Yes this is seen with a bit of frequency in the hospital. Usually anticoagulants are stopped for a short time and bleeds in GI tract explored and then clipped. Sometimes people undergo a secondary procedure to stop their need for a blood thinner (like an ablation) or they resume it on a short time after discharge.

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derefr t1_iw86odv wrote

Is there any kind of drug that does "change the viscosity or concentration of any component of blood"?

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ilostthegamespacedx t1_iw876sj wrote

In the strictest terms, yes. For example, Hydroxyurea decreases cell production in the bone marrow and can rapidly decrease a population of white cells called myeloid cells in the case of leukemia where the count can exceed 100,000. This is to prevent leukostasis which is where the cancerous cells thicken the blood and cause it to sludge causing respiratory failure or stroke.

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