Red Blood Cell Disorders: Background Flashcards
What do RBCs do?
Transport oxygen, CO2, CO, and HN03 (nitric acid) gases for exchange
Via the protein hemoglobin
Anemia definition
Low hemoglobin, RBC count, or hematocrit
Hematocrit definition
the % of RBCs
total blood volume
Polycythemia definition
elevated Hbg, RBC count, or hematocrit
What tests do you first use to assess for RBC disorders?
CBC
peripheral smear
What does a peripheral smear test?
morphology of RBCs
Where are RBCs made?
bone marrow stem cells
what hormone drives RBC production?
erythropoeitin (epo)
What organ secretes epo?
kidney
What items in our diet are needed to supply the bone marrow?
iron
folic acid
vitamin B12
protein
Life cycle of a RBC
- In bone marrow w/ nuclei
- Nuclei get extruded after all the Hgb is made
- RBC leaves the bone marrow w/ some RNA (this RNA stains as a reticulocyte)
- The reticulocyte matures into an RBC in 2 days
- This RBC circulates in the blood for 120 days
What does the reticulocyte count measure?
how the bone marrow is responding to a decrease in RBCs
How is reticulocyte count measured? (fraction)
raw reticulocyte count x patient Hgb
normal Hgb
What percentage of reticulocyte count indicates the bone marrow is working?
greater than 3%
What happens to RBCs after 120 days?
They are hemolyzed in the spleen, and Hgb is degraded into heme and globin.
Heme –> indirect bilirubin; transported to liver to become direct bilirubin
This gets stored in the gall bladder
What could high levels of indirect bilirubin indicate?
hemolysis or hereditary Gilbert syndrome
What could high indirect bilirubin PLUS high corrected reticulocyte, high LDH, and hemoglobinuria point to?
hemolysis
Hemoglobin definition
protein composed of different amino acid chains (alpha, beta, delta, gamma)
has 4 iron-containing heme groups
What types of Hgb are in everyone’s RBCs?
Hgb A, F, and A2
What Hgb is predominant in utero?
F
What Hgb is most dominant after birth?
A
What can decreased alpha- or beta-chain production cause?
thalassemia (alpha and beta types)
What is the most common hemoglobinopathy?
sickle hemoglobin (Hgb S)
What lab tests can be used to identify hemoglobinopathies?
hemoglobin electrophoresis
isoelectric focusing (IEF)
high-performance liquid chromatography (HPLC)
capillary zone electrophoresis (CZE)
What causes a hypocoagulable state?
platelet deficiency
factor deficiency (clotting factors, vWF, Vit K)
What causes a hypercoagulable state?
excess platelets
deficiency of anti-thrombotic proteins (protein C, protein S)
How do platelet problems usually manifest?
excessive/repetitive bleeding, bruising, or bleeding @ unusual sites
How do platelet problems & vWD present?
skin petechiae, bruising, increased mucosal bleeding (epistaxis, gums, menorrhagia)
How do coagulation defects typically present?
(e.g. hemophilia)
hemarthroses and deep tissue hematomas
What diagnostic studies are usually used for coagulation disorders?
CBC with platelet count, peripheral smear, and PFA (for ID and quantifying cellular changes)
PT (extrinsic clotting pathway) or INR
PTT (intrinsic clotting pathway)
TT (if either PT or PTT is prolonged)
metabolic profile (liver and kidney fn)
D-dimer (detects thrombosis)
What is the intrinsic clotting pathway?
indicates when there is damage inside a blood vessel
feeds into the common pathway (factors X, V, II)
What is the extrinsic clotting pathway?
indicates there is a tissue injury (outside the blood vessel)
feeds into the common pathway (X, V, II)
What does PT tell?
examines how long clotting takes in the extrinsic pathway, or common pathway
(Factors VII, X, V, II)
What does PTT tell?
examines how long clotting takes in the intrinsic pathway, or common pathway
(Factors XII, XI, IX, VIII, X, V II)
Which clotting factors work with Vitamin K?
II, VII, IX, X
Which lab value measures the effect of Coumadin? (which affects the Vit. K dependent factors)
PT
Which lab values tell you about Heparin’s effect? (which increases antithrombin III activity)
PPT
