vallia
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An increase in which of the following best explains the mechanism by
which the cardiac output increases in severe anemia?
A. Arteriolar diameter
B. Blood viscosity
C. Peripheral vascular resistance
D. Splanchnic blood flow
E. Tissue oxygen tension
please explain the answer, thanks
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| general malaise
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my guess is A due to increase in sympathetic outflow as a result of decreased oxygenation of tissues
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| doc179
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A
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| robin082006
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| general malaise
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sorry i meant E
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| drpkaur
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IN anemia,cardiac output increases because of decreased viscosityand the decreased oxygen content of the systemic arterial blood,leads to decreased oxygenation of tissues...so more blood must be pumped to supply the same amount of O2 to the tissues per unit of time...i thought is it E......correct me if am wrong plz.
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| doc179
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drpkaur the Q asks ; An "increase" in which of the following best explains the mechanism by
which the cardiac output increases in severe anemia?
tissue oxygen tension does not increase in anemia. there is hypoxia which is why the CO is increased in anemia.
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| vallia
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the answer is A, but I still didn't understand so please doc179 explain , thanks
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| doc179
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this is what I feel. the Q asks what " increases " among the choices in anemia that results in increased CO.
because of decreased heamoglobin concentration there is hypoxia ( that is decreased tissue oxygen tension ), peripheral vascular resistance must decrease in order to supply more blood to the hypoxic tissues to compensate for the decreased heamoglobin, decreased heamoglobin concentration reduces the number of RBCs in the blood hence blood viscosity is decreased. only arterial dilatation ( that is decreased TPR and increased blood flow ) can supply more O2 to the peripheral tissues.
Now abt the choice D, I hope someone else explains it in a better manner. But this is what I feel abt it: If the splanchnic blood flow decreases in anemia to sacrifice O2 for other vital organs , then it is not the answer to this Q as the Q asks what " increases "
If the splanchnic blood flow increases to supply more O2 to it by increasing blood flow ..the only reason for that change is increased arteriolar diameter that is decreased TPR. So again the best choice is A.
Hope that helps Vallia. GL
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| vallia
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Thanks, doc179, I got it. anemia leads to general arteriolar dilation, which means decrease in peripheral vascular resistance, . this means a decrease in afterload so an increase in stroke volume , ie increase in cardiac output. I hope that's it.
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| doc179
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yes thats abt it
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| drpkaur
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ya i think i was mistaken in accepting the choices, i think doc179 is right.....A
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