MLS 416 Red Cell Unit

Define total blood volume, including RBC mass and plasma volume

Total Blood Volume: the total amount of blood circulating (RBC mass + plasma volume)

Anemia

• Low RBC count

• Low HGB

• Low HCT

Hematologic responses of anemia

• ↓ RBC count, hemoglobin, and hematocrit → decreased oxygen-carrying capacity

• Kidneys sense tissue hypoxia and release erythropoietin (EPO).

  • EPO stimulates the bone marrow to increase erythropoiesis.

• Increased reticulocytes may appear in the blood if the marrow is capable of responding.

• Severe or prolonged anemia can cause increased release of immature RBCs and other erythroid precursors.

True vs pseudo anemia

• True anemia = too few RBCs

• Pseudo anemia = too much plasma

The two general mechanisms responsible for the development of anemia are:

1. Decreased RBC production: BM fails to produce enough RBCS to replace those lost normally from circulation

2. Increased red blood cell loss or destruction: RBCS lost from circulation faster than they can be replaced

Compare anemias of acute and chronic blood loss

	Acute blood loss	Chronic blood loss
Cause	Sudden hemorrhage	Slow, ongoing blood loss
MCV initially	Normocytic	Microcytic if iron deficiency develops
Iron stores	Initially normal	Decreased
Reticulocyte response	Initially normal/low, then increases	Increased if marrow can respond
Retic release	Begins about 3–5 days after blood loss	Continually increased as long as blood loss continues
Main reason	Not enough time for marrow to respond immediately	Chronic iron loss eventually limits RBC production

What are causes for a dimorphic/heterogenous population of red cells?

Common causes:

• Post treatment for a deficiency

• Two ongoing deficiencies

• Post-transfusion

• Sideroblastic anemia (idiopathic type)

Elevated RDW and an unreliable MCV if RDW >22% (may be falsely normal)

Compare compensated vs uncompensated hemolytic disease

Uncompensated hemolytic disease	Compensated hemolytic disease
Destruction > replacement	Destruction = replacement
Bone marrow is overwhelmed	Bone marrow can keep up
Anemia is present	No anemia
High reticulocyte count, but not enough to replace RBCs	High reticulocyte count
NRBCs may be present due to increased marrow activity	Usually no significant NRBCs
Severely shortened RBC lifespan	RBC lifespan is shortened, but replacement compensates
Abnormal RBC destruction/hemolysis tests	Abnormal RBC destruction/hemolysis tests

Compare intra vs extravascular hemolysis

Intravascular hemolysis	Extravascular hemolysis
RBCs are destroyed within blood vessels	RBCs are destroyed by macrophages in the spleen and liver
Free hemoglobin released directly into plasma	Hemoglobin is broken down within macrophages
Hemoglobinemia	↑ Bilirubin
Hemoglobinuria	No hemoglobinuria
Markedly ↓ haptoglobin	Haptoglobin may be normal or decreased
Can cause hemosiderinuria with prolonged hemolysis	Splenomegaly is common
Examples: mechanical destruction, complement-mediated hemolysis	Examples: hereditary spherocytosis, many antibody-mediated hemolytic anemias

Define polycythemia/erythrocytosis

An increase in red blood cell mass, resulting in increased RBC count, hemoglobin, and hematocrit

Compare true/secondary and pseudo/relative polycythemia

True/Secondary Polycythemia	Pseudo/Relative Polycythemia
Actual increase in RBC mass	Normal RBC mass; plasma volume is decreased
Usually caused by increased EPO due to hypoxia	Caused by dehydration/fluid loss
Causes: high altitude, smoking, chronic lung disease, heart disease, EPO-producing tumors	Causes: vomiting, diarrhea, excessive sweating, dehydration
EPO ↑ in secondary polycythemia	EPO usually normal
RBC count ↑	RBC count may appear ↑ due to hemoconcentration
Hgb ↑	Hgb ↑
Hct ↑	Hct ↑
RBC mass is truly increased	RBC mass is not actually increased

Compare pseudo polycythemia vs pseudo anemia

Pseudo Polycythemia (Hemoconcentration)	Pseudo Anemia (Hemodilution)
Plasma volume decreases	Plasma volume increases
RBC mass is normal	RBC mass is normal
Blood becomes more concentrated	Blood becomes more diluted
Hgb appears increased	Hgb appears decreased
Hct appears increased	Hct appears decreased
Common cause: dehydration/fluid loss	Common cause: excess fluid or IV fluids

Describe the reticulocyte

Reticulocyte: immature RBC released in the bloodstream before it fully matures

• Composition: residual RNA that can be visualized with a supravital stain (new methylene blue) and shows polychromasia

• Time spent in BM: ~2-3 days after nucleus extrusion,

• Time spent in blood: 1-2 days before maturing into an erythrocyte.

• Maturation: in circulation within 3-5 days after blood loss

Describe the mature erythrocyte

• Function: transport oxygen from lungs to tissues via hemoglobin

• Lifespan: 120 days

• Membrane: biconcave; made of protein shell (spectrin) heavily coated with lipids. Semi-permeable; controls volume by decreasing sodium and increasing potassium content

• Destruction: Senescent/damaged RBCs removed by macrophages

  • Hemoglobin: globin breaks down into amino acids, iron removed from heme and recycled; polyphyrin ring is converted to bilirubin

What is the function of spleen?

• Filters blood by removing old or damaged red blood cells

• Stores blood and platelets

• Fights infections by producing and storing WBCs

• Recycles iron

State the composition of the following RBC inclusion bodies, including stains used to detect:

a. Howell-Jolly bodies

b. Pappenheimer bodies

c. Basophilic stippling

d. Heinz bodies

Inclusion	Composition	Stain used to detect
Howell-Jolly bodies	DNA remnants (nuclear chromatin)	Wright-Giemsa
Pappenheimer bodies	Iron-containing granules (ferritin/hemosiderin)	Prussian blue (iron stain); also visible with Wright-Giemsa
Basophilic stippling	Aggregated ribosomal RNA	Wright-Giemsa
Heinz bodies	Denatured/precipitated hemoglobin	Supravital stains

What are recombinant cytokines, and what are they used for?

Recombinant cytokines: cytokines manufactured with DNA technology for clinical use

• Ex: EPO, GM-CSF, G-CSF

Purpose: stimulates recovery after potent chemotherapy or transplant, or after anemias

• Reduced duration of severe blood cytopenias

• GM-CSF produces an extreme leukocytosis and marked left shift with toxic neutrophils

Describe the principle of the Sugar water and Donath-Landsteiner tests.

Test	Principle	Disorder
Sugar water test	Patient RBCs are placed in acidified, low-ionic-strength sucrose solution. In PNH, RBCs have increased sensitivity to complement-mediated lysis, causing hemolysis and a positive test.	PNH
Donath-Landsteiner test	Detects the biphasic hemolysin (Donath-Landsteiner antibody) found in PCH. Patient serum is incubated with RBCs at cold temperature, allowing antibody to bind. The mixture is then warmed to 37°C, causing complement activation and intravascular hemolysis.	PCH

NOTE: Flow cytometry also used to diagnose PNH by detecting decrease/absence of CD55/59

If marrow demand exceeds the capacity of normal marrow during severe anemia, where may additional RBC production occur?

Liver and spleen

• extramedullary hematopoiesis

• organs responsible for RBC production during fetal development

What is ferritin?

A protein that stores iron inside your cells

What is transferrin?

A protein that carries iron to your organs. Iron normally circulates in plasma bound to transferrin.

What is TIBC?

Total Iron-Binding Capacity

• Measures blood’s ability to attach to iron and carry it through the body

• Measures transferrin

High TIBC = high amount of transferrin with very little iron attached

Low TIBC = transferrin mostly full or decreased amount of transferrin

What inflammatory mediators are specifically linked to increased acute-phase reactants in ACD?

IL-6 and IL-1

Why is TIBC often decreased in anemia of chronic disease?

Inflammation decreases transferrin synthesis

What is iron chelation used for?

Removes toxic excess iron from chronic transfusions

Which laboratory enzyme is often increased in megaloblastic anemia?

LDH (lactate dehydrogenase)

• Driven by ineffective erythropoiesis and intramedullary hemolysis

Why are spherocytes more osmotically fragile than normal RBCs?

They have a decreased surface-area to volume ratio

What is pancytopenia?

Low RBCs, WBCs, and PLTs

How would you treat HDFN due to ABO incompatibility?

Phototherapy (Glo-worm)

How would you treat HDFN due to Rh incompatibility?

Exchange transfusion in utero or at birth

Why is HDFN due to Rh no longer a common problem?

RhoGam use

How would you treat PCH?

Eculizumab - anticomplement antibody

Avoid the cold

What is the pathogenesis of PCH?

Idiopathic or associated with viral infection

What are complications of PNH?

• thrombosis (abnormal plts)

• infections (low WBC count)