Sepsis shock (SV vs. CO)

[acciddropping]

Hey guys,
In septic shock, can you explain the status of stroke volume and cardiac output? Are they increased or decreased? Thanks!

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[Fox800]

Low BP --> decreased baroreceptor input --> increased sympathetic output, so those catecholamines are going to try to compensate for low BP by increasing stroke volume and cardiac output. TPR is decreased in septic shock, so the body will try to maintain CO by increasing HR.

 

[Venko]

Low BP --> decreased baroreceptor input --> increased sympathetic output, so those catecholamines are going to try to compensate for low BP by increasing stroke volume and cardiac output. Remember that CO = SV x TPR.

I think CO = SV x HR

 

[Fox800]

I think CO = SV x HR

You're right, I goofed up. Boards studying turned my brain into mashed potatoes.

 

[acciddropping]

Cool - in DIT, it was saying that CO is increased, which I agree. But it also says SV is decreased, which I did not get. Yes, it's CO = SV x HR

 

[Venko]

Cool - in DIT, it was saying that CO is increased, which I agree. But it also says SV is decreased, which I did not get. Yes, it's CO = SV x HR

It's been a long time since I've reviewed this carefully but since SV is directly related to preload and contractility and inversely related to after load...te contractility will increase from the catecholamines, but the preload goes way down because of vasodilation peripherally. After load is not terribly affected I think.

This causes the SV to change from initially high in early sepsis to much lower in late sepsis and septic shock.

 

[acciddropping]

It's been a long time since I've reviewed this carefully but since SV is directly related to preload and contractility and inversely related to after load...te contractility will increase from the catecholamines, but the preload goes way down because of vasodilation peripherally. After load is not terribly affected I think.

This causes the SV to change from initially high in early sepsis to much lower in late sepsis and septic shock.

It makes sense now. Thanks!!

 

[thehundredthone]

I posted a little bit about this in a similar thread: http://forums.studentdoctor.net/posts/15054847/

 

[Venko]

I posted a little bit about this in a similar thread: http://forums.studentdoctor.net/posts/15054847/

That is a great description. I would add the part about late septic shock where CO is no longer high because the drop in preload has severely outpaced the increased contractility and heart rate.

 

[acciddropping]

I get confused because some charts I read contradict each other - But, below is how I think of these shocks now... please correct me if I am wrong.
a) SVR and CO are almost always inversely related.
b) think of PCWP as preload

In septic shock, it feels warm to touch, so SVR is low (vasodilation), CO is increased initially and decreased terminally and PCWP is low in both cases.
In hypovolemic shock, it feels cold to a touch, so SVR is high (vasoconstriction), CO is decreased and PCWP is decreased (bc preload decreases)
In cardiogenic shock, CO is decreased, hence, SVR is increased, and PCWP is increased (which is unique to cardiogenic shock, perhaps bc of increased preload)

Thanks

 

[thehundredthone]

That is a great description. I would add the part about late septic shock where CO is no longer high because the drop in preload has severely outpaced the increased contractility and heart rate.

Done.