drug of choice for hypotension with renal dz

[MudPhud20XX]

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So FA lists two drugs, norepinephrine and phenylephrine for DOC for hypotension. But with renal dz, you wouldn't give norepinephrein, so to keep the renal perfusion and to treat hypotension, would phenylephrine be a better choice? Since it doesn't affect and beta 1 which stimulates renin release and thus maintain renal perfusion? Many thanks in advance.

 

[Cytarabine]

Hypotension isn't a homogenous condition. You treat based on etiology. Neither is renal disease for that matter

 

[Instatewaiter]

So FA lists two drugs, norepinephrine and phenylephrine for DOC for hypotension. But with renal dz, you wouldn't give norepinephrein, so to keep the renal perfusion and to treat hypotension, would phenylephrine be a better choice? Since it doesn't affect and beta 1 which stimulates renin release and thus maintain renal perfusion? Many thanks in advance.

So it's not that simple.

First, let's take sepsis, the more common cause of hypotension. Here because of the hypotension from the sepsis you get poor renal perfusion. The vasodilation causes low SVR which in turns activates your sympathetic system. Sympathetic activation causes afferent arteriole and therefore your GFR drops

Second, phenylephrine cuases more vasoconstriction and if anything could make the above worse.

 

[worldbeater]

Sympathetic activation causes afferent arteriole and therefore your GFR drops

Basic question, I thought sympathetic activity would cause a constriction of your efferent, than you would have a backflow and an increase in your GFR? Due to angiotensin II, like in RAAS, or we talking about two different things?

Just wanted to clarify because I wrote that about about RAAS in another post and want to make sure I was right or not.

 

[Instatewaiter]

Basic question, I thought sympathetic activity would cause a constriction of your efferent, than you would have a backflow and an increase in your GFR? Due to angiotensin II, like in RAAS, or we talking about two different things?

Just wanted to clarify because I wrote that about about RAAS in another post and want to make sure I was right or not.

Sympathetic activity constricts the afferent and efferent. Constriction of either will decreased renal blood flow. As I remember it, sympathetic activity constricts your afferent more than your efferent causing the pressure difference that drives filtration (ie your GFR) to decrease. So sympathetic activity constricts both but the afferent more. Your GFR drops as does your renal blood flow. This is part of the reason your urine output plummets in shock.

And since we are talking about drugs, we are talking about direct sympathetic activation. This will in turn activate renin but there are direct effects as well