Hematology Basics (3) Flashcards
What is hematology
The study of blood and its components
What are the components of blood
Plasma - 55%
-salt, water, enzymes, antibodies
Red blood cells - 45%
-important for oxygen transport throughout the body
White blood cells and platelets - 1%
-WBCs - protection for infections
-platelets - coagulation proteins that allow body to manage clotting
What is hematopoiesis?
The production of ALL types of blood cells (includes formation, development, and differentiation of cells)
What are low and high platelet counts called?
Low - thrombocytopenia
High - thrombocytosis
What are low and high RBC counts called?
Low - anemia
High - polycythemia
What are low and high WBC counts called?
Low - leukopenia
High - leukocytosis
What lab values do we look at to see if a patient has anemia? (2)
Hemoglobin
Hematocrit (percentage of blood that is made up by RBCs)
What lab value do we look at to see if a patient has thrombocytopenia?
Platelets
What is pancytopenia?
deficiency of all three cellular components of the blood (red cells (Hgb), white cells, and platelets) - so we look at all 3 of these values
What is anemia?
Reduction in the bodies ability to transport oxygen to organs that need it
-can be due to reduction in hemoglobin or hematocrit (RBCs)
Anemia is more prevalent in which patients?
Patients with CKD
Older patients - over 65 yo
Women (bc of pregnancy and menstrual bleeding)
African descent (typically have lower Hgb values)
Which 2 factors may cause someone to have higher Hbg/RBCs
People who live at higher elavations have higher levels of hemoglobin
High endurance athletes have higher levels of RBCs
What is the lower limit of normal of hemoglobin for males and females
Males: 13 g/dL
Females: 11 g/dL
(anything below this, we start thinking about potential therapy for these patients)
National cancer institute anemia scale
Grades 1 - 5 … the higher the grade the lower the level of hemoglobin
Grade 1
-Hgb of 10 - < LLN (13 for males 11 for females)
Grade 2
-Hgb of 8 to <10
Grade 3
-Hgb of 6.5 to <8
Grade 4
-Hgb of <6.5
Grade 5
-Death
What is the role of RBCs? How does this relate to anemia?
RBCs pick up oxygen from the lungs and release CO2 into the lungs
Then they transport the oxygen to the rest of the body
-anemia is a disorder where a patient has tissue hypoxia due to a lack in this oxygen transport
Erythropoietin (EPO)
This is a hormone that is produced primarily in the kidney
It stimulates the synthesis/differentiation of erythroid progenitor cells (which are precursors for RBCs) (reticulocytes)
So EPO is important for the production of RBCs
(which is why people with CKD are more prone to anemia, since EPO is made mostly in the kidney)
Mean corpuscular volume (MCV)
This is a lab value of the average size of the red blood cells
-used to determine if the cells are large or small
Normoblastic vs megablastic
This refers to the shape of the RBC
Normoblastic = normal shape, which is circular/round
Megablastic is more of an oblong/oval shape
Normochromic vs hypochromic
This refers to the color of the RBC
Normochromic = normal bright red color
Hypochromic = faded color (usually means there is less hemoglobin and therefore impaired oxygen carrying capacity)
How does the body react to anemia? (3)
When a patient has anemia there is a decreased oxygen carrying capacity
The body tries to compensate by…
-increasing blood flow
-increasing RBC mass
-increasing oxygen unloading
This makes sense as it is explained by the relationship in this equation…
VO2 = 1.39 x Q x Hgb x (SaO2 - SvO2)
-if there is a decrease in Hgb, to keep VO2 the same, the body will try to increase Q (blood flow) and oxygen unloading (SaO2 - SvO2)
Compensating for anemia - increase in blood flow
Because of decreased oxygen transport with anemia, the body tries to compensate by increasing blood flow (Q)
The heart pumps harder and faster resulting in increased cardiac output
This can result in tachycardia and murmurs/arrhythmias
And if it continues for a long period of time can lead to heart failure
When the body compensates in the anemic state to increase blood flow, which organs get the blood?
The vital organs (the ones that desperately need blood to function)
-brain, heart, kidneys
Compensating for anemia - increase in RBC mass
The body tries to increase the mass of RBCs to increase oxygen transport (to compensate for the anemic state)
In order to do that it increases the production of EPO in the kidneys (to increase production of reticulocytes)
Overtime this can lead to hyperviscosity in the blood, which can result in bone pain (pain occurs as bone marrow tries to expand to compensate for increased amount)
What are some causes of anemia (5)
- Production defects
-deficiency in EPO (seen with kidney disease)
-seen in cancer patients
-inability to produce RBCs - Maturation defects
-typically cancer associated (cancer kills bone marrow, where RBCs mature) - Survival defects
-RBC cannot survive after it is produced
-Can be intrinsic (something is wrong inside the RBC that keeps it from surviving) or extrinsic (RBC is being attacked from the outside, e.g. a toxin) - Sequestration
-splenic sequestration, particularly in hemolysis - spleen takes up RBCs (causing anemia) - Blood loss
-hemorrhage, GI bleed, etc.
-could be due to conditions that require a lot of blood work/labs
Reticulocyte counts
Reticulocytes are immature RBCs
We don’t want RBCs to stay immature, so this value should typically be less than 1%
Patients who are constantly producing new RBCs (e.g. sickle cell anemia or another disorder where they need to be constantly replacing RBCs) may have an elevated reticulocyte count
Or if a patient is bleeding or undergoing hemolysis - they will have more reticulocytes since they are trying to compensate and create more RBCs for the ones they are losing
Mean cell hemoglobin (MCH)
Measure of the weight of Hb in a single RBC.
(used to make sure there is adequate amount of hemoglobin)
Mean cell hemoglobin concentration (MCHC)
measurement of the amount (weight) of hemoglobin in a single RBC compared to the volume of the cell
(used to see if the amount of hemoglobin present is appropriate for the size of the cell to carry the oxygen needed)
Macrocytic vs microcytic anemia
Macrocytic (MCV > 100)
-RBCs are LARGER than normal
-caused by folic acid deficiency or vitamin B12 deficiency
Microcytic (MCV < 80)
-RBCs are SMALLER than normal
-caused by iron deficiency (which results in reduced hemoglobin synthesis)
-aka iron deficiency anemia (IDA)
Note - in both marco and microcytic anemia the cells may be normal shaped (normoblastic) but are larger or smaller in size
Note - normal sized cells are called normocytic (MCV 80-100)
If we have a decreased RBC production, what is the first step/first thing to look at?
The size of the RBCs… are they….
-microcytic (MCV < 80)
-normocytic (MCV 80-100)
-macrocytic (MCV > 100)
If RBCs are microcytic what should you consider next to determine the cause of decreased RBC production?
The color…
If they are normochromic (bright red)…
-genetic cause (we may or may not have to do anything about this)
If they are hypochromic (faded) …
-means they do not have enough Hgb (low MCH and MCHC)
-this could be IDA (iron deficency) or anemia of chronic disease (caused by CKD or chronic inflammatory state)
If RBCs are normocytic what is likely the cause of decreased RBC production?
Bone marrow failure –> cancer related
Or associated with CKD
Or can occur if a patient has causes of both macrocytic and microcytic anemia (results in normocytic)
If RBCs are macrocytic, what should be considered next to determine the cause of decreased RBC production?
Is the shape appropriate?
If they are megablastic…
-caused by folic acid or vitamin B12 deficiency
If they are normoblastic (normal shape) - the cause is harder to identify…
-can be due to alcohol use, liver disease, hyperthyroidism, HIV medications, valproic acid , or other random causes
