phenylephrine question

[greenseeking]

How does phenylephrine decrease venous return to the heart?

In one of the Uworld question explanations, it says phenylephrine vasoconstricts, which decreases cardiac output and increasing venous return.

Shouldn't it increase venous return to the heart since the alpha 1 agonist works as a vaso and veno constrictor? Thanks in advance.

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[Anti-PD1]

How does phenylephrine decrease venous return to the heart?

In one of the Uworld question explanations, it says phenylephrine vasoconstricts, which decreases cardiac output and increasing venous return.

Shouldn't it increase venous return to the heart since the alpha 1 agonist works as a vaso and veno constrictor? Thanks in advance.

Alpha 1 vasoconstriction keeps blood in the arterial side, decreasing venous return, decreasing preload, and so, decreasing CO.

 

[Northerncardinal]

Initially, cardiac output would increase cuz of venoconstriction but later on cardiac output would decrease due to increased afterload.

 

[greenseeking]

Alpha 1 vasoconstriction keeps blood in the arterial side, decreasing venous return, decreasing preload, and so, decreasing CO.

Thanks! But but the alpha-1 agonist action on the veins should increase preload/increase venous return right? Maybe I'm just over thinking this.

 

[greenseeking]

Initially, cardiac output would increase cuz of venoconstriction but later on cardiac output would decrease due to increased afterload.

Thank you. I think I'm going to have to think about this for awhile.

 

[Northerncardinal]

Thank you. I think I'm going to have to think about this for awhile.

this topic was a pain long time ago for me as well..i kept searching and found some study that had this explanation which made sense.