hey guys I have a pretty basic question about cardiac output and its relation to mean arterial pressure that I can't seem to figure out. When afterload goes down this makes cardiac output go up but I saw that this also makes MAP go down. Why is that? The equation MAP=COxTPR makes it seem as if they should be proportional to each other. Thanks!
Cardiac Output and MAP
- Thread starter cwaranch
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Because the biggest affect on afterload is likely to be TPR. If TPR goes down in such a way that it decreases MAP, then CO will increase to compensate and try to keep MAP constant. This is what happens with drugs like hydralazine that cause reflex tachycardia; the heart increases sympathetic stimulation in order to try and maintain blood pressure in response to the vast decrease in TPR.
I think it is always important with physiology to think of most equations as loose guides. The way these variables work in a biological system is more complex than a 3 number math equation.
I think it is always important with physiology to think of most equations as loose guides. The way these variables work in a biological system is more complex than a 3 number math equation.
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Hope this will help.
MAP=2/3DBP+1/3SBP
DBP is proportional to TPR(Afterload)
So, by extension if afterload goes down then MAP(DBP) would also go down.
TPR and CO:
Since decrease in resistance causes increased flow. Physics---> (P1-P2)=Q.R
MAP=2/3DBP+1/3SBP
DBP is proportional to TPR(Afterload)
So, by extension if afterload goes down then MAP(DBP) would also go down.
TPR and CO:
Since decrease in resistance causes increased flow. Physics---> (P1-P2)=Q.R
