Question about ischemia according to Goljan's RR Path,,, discrepancy

[Knicks]

On the 1st page it says that ischemia is defined as, "Decreased arterial blood flow or venous blood flow".

But I was listening to the audio* and he says it's a "decrease in arterial blood flow, not venous, arterial".

So as you can see, in the audio he goes out of his way to emphasize ARTERIAL, but in the RR BOOK, it says arterial OR venous.


Can anyone explain this discrepancy?



(*It's not mine, ok? So relax, my classmate lent it to me.)

[Saluki]

Originally Posted by Knicks

On the 1st page it says that ischemia is defined as, "Decreased arterial blood flow or venous blood flow".

But I was listening to the audio* and he says it's a "decrease in arterial blood flow, not venous, arterial".

So as you can see, in the audio he goes out of his way to emphasize ARTERIAL, but in the RR BOOK, it says arterial OR venous.


Can anyone explain this discrepancy?



(*It's not mine, ok? So relax, my classmate lent it to me.)

Maybe in the book, he's considering portal vein flow, where the venous blood is providing the oxygen supply...

Not sure, otherwise...

[bambi]

Originally Posted by Knicks

On the 1st page it says that ischemia is defined as, "Decreased arterial blood flow or venous blood flow".

But I was listening to the audio* and he says it's a "decrease in arterial blood flow, not venous, arterial".

So as you can see, in the audio he goes out of his way to emphasize ARTERIAL, but in the RR BOOK, it says arterial OR venous.


Can anyone explain this discrepancy?



(*It's not mine, ok? So relax, my classmate lent it to me.)

Yeah, I listened to that too, just the other night, and he does make a point of stressing arterial. Haven't looked at the book yet though. Maybe look it up elsewhere and see which it agrees with. If not I'm sure someone will tell you.

[Redrox]

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[Knicks]

^^ Exactly, so I'm assuming that this is another error in the RR book? (which was not mentioned in goljan's errata sheet).

[Monica Lewinsky]

I think the concept to know is that ischemia is the lack of a supply of oxygenated blood to a tissue bed. There are cases where venous occlusion can create ischemia (testicular torsion), but ultimately the supply of the oxygenated erythrocytes through the arteries is the reason why ischemia occurs in those cases.

[pseudoknot]

Anytime there is no redundant venous drainage, venous occlusion will cause ischemia. This is also the way I've seen it presented in other sources.

[Chutku]

the way I understood ischemia in school was-
lack of blood flow so tissues are unable to get oxygenated blood(so arterial blood)
inability of the body to remove metabolites and waste from tissue
decreased ability of getting nutrients


Dr. G just highlighted the major point

[MattD]

This.

Originally Posted by Monica Lewinsky

I think the concept to know is that ischemia is the lack of a supply of oxygenated blood to a tissue bed. There are cases where venous occlusion can create ischemia (testicular torsion), but ultimately the supply of the oxygenated erythrocytes through the arteries is the reason why ischemia occurs in those cases.

This is overstudying by the way. The test is not going to ask you what ischemia is. It's just too basic of a concept, IMO.

[Knicks]

^^ Of course the test is not going to ask us what ischemia is, but when applying the concept, it would be practical to know which definition is the correct one.

[Monica Lewinsky]

Originally Posted by MattD

This.



This is overstudying by the way. The test is not going to ask you what ischemia is. It's just too basic of a concept, IMO.

Its a concept which should just come naturally. Goljan includes it for completeness.

[PathGirl51]

If you look at the root words: isch - restriction, hem- blood, so the definition is the restricted flow of blood (assuming oygenated blood) to a cell/tissue. Goljan was initally right in that it can occur in an artery or vein. Generically, ischemia occurs in the artery in the marjority of clinically significant disorders .

The confusing aspect is that not all arteries carry oxygenated blood.

By definition an artery is a vessel that is involved in blood flow away from the heart (aorta, coronary artery, pulmonary artery, etc), while vein is involved with blood flow to the heart (vena cava, femoral, pulmonary vein, etc).

The majority of arteries in our body have oxygenated except for the pulmonary artery which brings de-oxygenated blood to the lungs (it's name an artery because the vessel is carrying the blood flow away from the heart). So, if a large pulmonary embolus plugs up the pulmonary artery, then a pumonary ischemia/infarction can occur if the bronchial arteries cannot compensate (lung has dual blood supply).

Someone mentioned the portal vein. Just wanted to clarify that this vessel carries de-oxygenated blood from the sup mesenteric & splenic veins and drains into the central vein. It does not provide oxygen supply to the liver.

Also, someone mentioned venous occlusion & testicular torsion. The torsion twists the arterial vessels & causes ischemia, so venous occlusion does not cause testicular ischemia. It's important to note that clinically, ischemia is used in the context of hypoxia of cells/tissue, whereas venous occlusion is associated with abnormal blood flow, stasis and edema-and does not contribute to ischemia

hope this helps. I teach Path btw...The Goljan review (green paperback) book that I have just states arterial probably just to minimize confusion

[rahulb]

Originally Posted by PathGirl51

Someone mentioned the portal vein. Just wanted to clarify that this vessel carries de-oxygenated blood from the sup mesenteric & splenic veins and drains into the central vein. It does not provide oxygen supply to the liver.

the liver is oxygenated by both the portal vein and hepatic artery

[Slide]

Originally Posted by Knicks

On the 1st page it says that ischemia is defined as, "Decreased arterial blood flow or venous blood flow".

But I was listening to the audio* and he says it's a "decrease in arterial blood flow, not venous, arterial".

So as you can see, in the audio he goes out of his way to emphasize ARTERIAL, but in the RR BOOK, it says arterial OR venous.


Can anyone explain this discrepancy?



(*It's not mine, ok? So relax, my classmate lent it to me.)

Goljan's one-liner on page 1 of RR Path is actually correct if you go by the textbook. Baby Robbins states ischemia the way Goljan states it (pg. 7 on the latest edition). I think the discrepancy for this is that ischemia is essentially tissue depravation of metabolic nutrients and statis of waste products, but the more important factor is the lack of nutrients, namely oxygen. This is obviously true for reduced arterial flow, but decreased venous blood flow can fit this definition in two ways:
1) pulmonary veins (as PathGirl) noted, and
2) whenever you have venous damming, it becomes harder for arterial blood to oxygenate the dammed area because of resistance and dilutional effects. For instance, when the IVC is dammed up for some reason (hypertension, polycythemia vera, etc.), it becomes harder for arterial blood to oxygenate zone 3 of the liver sinusoids due to the slower flow of blood. The defect lies in the flow of venous blood, not arterial blood, though arterial blood is still being impeded. Thus, ischemia and possible centralobular necrosis will occur.

But this is being really picky. I suppose the better way to define it is reduced oxygenated blood or something.