Clinical Approach to Anemia



so up to this point we've had a pretty whirlwind tour of all the anemias we started off by talking about the different type of cells in the blood and discussing how they develop in the bone marrow we next move to talking about hemoglobin and the different hemoglobinopathies and how this results in Amala sis and hemolytic anemia we then talked about the microcytic anemias including iron deficiency anemia of chronic disease and thalassemia and in the video just before this we talked about the macrocytic anemia which are mainly caused by deficiencies of vitamin b12 and folic acid now in this video we're going to be putting it all together trying to figure out how we can diagnose a patient who presents with anemia and trying to decide if it's a hemolytic anemia microcytic anemia or a macrocytic anemia now the best way to do that is just to go back to our handy-dandy flow chart the one we've been using for a number of videos now to remind us of the mechanism behind hemolytic anemia or the microcytic and macrocytic anemia and I'll just use little m / Big M with an A next so it didn't note microcytic and macrocytic anemia is respectively now we know in the hemolytic anemias this is due to increased removal and this gives us a drop in our B C's and we know that the microcytic and macrocytic anemia is are due to a change which we know is really a drop in production and this gives us our decrease in our BCS and we know that both of them have a decrease in our B C's because that would be our definition of anemia if you're ever working up a case and get confused as to what type of anemia you're dealing with you can always come back to this flow chart and if you figure out you have increased removal or decreased production that'll help you a lot in terms of figuring out what type of anemia you're actually dealing with so let's say we have a patient who's denoted by this stick figure right here and they come to you and you're able to diagnose them with an anemia but now the question is what kind so what do you do to figure out if it's a microcytic anemia a macrocytic anemia or a hemolytic anemia and the best tool we have is really to look at the reticulocytes in the blood so let's just go ahead and draw an arrow indicating looking at and we'll say reticulocyte s– because this is going to help determine what type anemia we're dealing with if you remember reticulocytes are the slightly immature form of red blood cell and normally they're about one percent of the total circulating our pcs so if we have less of them or more of them it can help indicate what type of shape our bone marrows in and if you're over producing or under producing the amount of cells so there's really only two options here when it comes to our level of reticulocytes we can either have a decrease in reticulocytes or we can have an increase in it in reticulocytes now decrease is going to indicate either a microcytic or macrocytic anemia while an increase in reticulocytes is going to give us a hemolytic anemia so let's first take a look at the microcytic and microcytic anemias first and we'll start off by talking about the mechanism for the decrease in reticulocytes so the question here is why why do we get a decrease in reticulocytes now we know that in the microcytic and macrocytic anemia is we have problems in either DNA or hemoglobin production and because these are critical components of these cells this leads to bad production of cells now because these are so critical the cells can't develop as they normally would so we have a decrease in cell production and because reticulocytes are a type of cell and that they'll develop into RBC's we get a drop in reticulocytes well let's look at this schematic of a red blood cell and we'll figure it out on the right side here we have the macrocytic so I'll put a big m to denote that and on the left here we have a microcytic RBC so we'll put a little tiny m to denote that now on the macrocytic side this is because we have a drop in DNA production because these cells stay in g2 so long they don't actually enter the M phase until they're huge and this leads to really big cells so what can cause a macrocytic anemia well there's really only two causes and it's deficiencies in either b12 or folate in both of these cases the presence of a hyper segmented poly is enough to diagnose a patient with macrocytic anemia the microcytic anemias on the other hand are a little bit different these are caused by decreased hemoglobin synthesis and because hemoglobin takes up a significant amount of space inside the RBC if we're not making hemoglobin as normal these cells are going to be really small and there's going to be less of them now the major cause of microcytic anemias is an iron deficiency so I'll just say decrease in iron but there are other causes as well you can have anemia of chronic disease which is basically a functional iron deficiency where the body is trying to hide iron from organisms such as bacteria that might want it this could also be due to one of the hemoglobinopathies thalassemia which causes defective hemoglobin to be produced and there's some other less common causes as well like lead or heavy metal toxicity or The Sitter elastic anemias which is where hemoglobin is stored inside the mitochondria where it's unable to be used in its normal capacity now it's easy to tell macrocytic versus microcytic when you're looking this close to an RBC but in the real world will use the MCV and on the macrocytic side that's going to be a measurement of greater than 100 femtometers and on the microcytic side that's going to be less than 80 femto liters so now that we've gotten a good look at the macrocytic and microcytic anemias let's take a look at the hemolytic anemias so again we're going to want to answer the same question only now it's why do we have an increase in reticulocytes in all of the hemolytic anemias the process starts with RBC damage and this could be for a number of reasons which we'll go through in just a second but this RBC damage leads the hemolysis and this hemolysis is what causes our hemolytic anemia in response to this hemolysis or this drop in red blood cells we have a compensatory reaction we have a red hyperplasia which is an increase in RBC precursors in the bone marrow but because these precursors can't be produced fast enough to keep up with a destruction of RBC's we end up with hemolytic anemia so what causes hemolytic anemia well there's a number of causes divided into two categories but let's take a look at them by examining this RBC the first set of causes are intrinsic and we'll go ahead and discuss them here inside the RBC because their properties of the RBC's themselves that are deficient and just to help you remember all of these intrinsic causes of hemolytic anemia and in appa theis so there's three main kinds of appa these the first is the hemoglobinopathies and this include sickle-cell anemia and thalassemia there's the ends of mapa thiis and this is due to something like g6pd deficiency or there's the member napa thiis and this can be hereditary spherocytosis or hereditary ellipta psychosis and all of these cause hemolytic anemia because they predispose this red blood cell to being prematurely removed the other set of causes of hemolytic anemia are the extrinsic causes and there's a couple more of these there's immune mediated hemolytic anemia which attacks certain antigens on the red blood cell surface with antibody and predisposes them to being removed from circulation by the immune system there's the clotting disorders like di C and TTP which both cause the sheering of red blood cells to form schistocytes there could be other extrinsic causes infectious diseases like malaria for instance which can predispose these red blood cells to destruction because they're invaded by the parasite that causes malaria there's something called fetal Rh incompatibility which I'll just abbreviate like so and this is due to the fact that you have an Rh negative mother and an Rh positive fetus and the subsequent Rh positive fetus is going to be potentially attacked by the mother's immune system but fortunately this can be blocked with the drug rhogam and the last one is due to transfusions and interestingly two transfusions the patient's blood cells aren't being attacked it's the new blood cells that are being transfused in that are being attacked but because they're inside this one person's body we call it a hemolytic anemia because the red blood cells are going to be destroyed now another way of looking at all these causes is whether their immune mediated or not and I'll just put a little green triangle to denote causes at our immune so immune mediated hemolytic anemia along with fetal Rh incompatibility and transfusion mediated hemolytic anemia are the only three causes that have to do with the immune system the rest of the causes are not immune mediated but you can divide them into extrinsic and intrinsic causes if you so wish so we've now had a quick review of the causes of both hemolytic anemia and macrocytic and microcytic anemia as well as how they cause an increase or a decrease in reticular sytze respectively by remembering these changes as well as remembering the changes in production and the changes in removal that lead to these different types of anemia you should have no problem diagnosing these when you see them on the wards

17 comments

  1. I dont understand, does Thalassemia cause an increase or a decrease in the reticulocytes? Because in the video, we see that it is both a micro anemia and a hemolytic anemia???????

  2. In your video on Macrocytic anemias you said that the number of immature RBCs goes up in the bone marrow (3:28 – 3:53). Here you say it goes down… Are you talking here about serum levels?

  3. Once again, thank you for this video, this series has been amazing. Curious question, what exactly is your job / what do you study? your videos span many topics it's hard to pinpoint haha

  4. i keep wondering why peripheral circulation is important in the diagram? i can think of acute blood loss/ chronic disease states/ severe coagulopathies, but what else does it include? and where does normocytic anemia fall into in the diagram? maybe you can define what you mean by peripheral circulation? cheers!

  5. Thanks! You can sign up for the YouTube HTML5 at youtube (dot) com (slash) html5 which will allow you to speed up or slow down youtube videos.

  6. Your anemia videos are comprehensive and excellent! Thank you :D. I am in medical school now and am watching these as a good review.

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