Erythropoiesis Flashcards
Where to red blood cells come from?
blood stem cell–> myeloid stem cell–> RBC
Red Blood Cell (RBC) Function
RBCs are highly specialized end-stage cells **without a nucleus (after release into peripheral blood) that transport O2 and CO2
RBC hemoglobin binds O2 in a high pO2 environment and releases oxygen in a low pO2 setting. It is the ability to “let go” or release O2 that is the unique attribute of hemoglobin within a RBC.
RBC lifespan.
What happens to them as they age?
Survival is ~ 100 to 120 days. As red cells age, they become smaller (less than 8 microns in diameter) and become less elastic (do not deform as well to pass through capillaries).
Regulation RBC Production
RBC progenitor cells directly regulated by erythropoietin (EPO), a glycoprotein produced and released by peritubular capillary lining cells of the kidney
EPO in turn regulated by PO2….that is the amount of oxygen available to the kidney
When **hemoglobin levels fall below 10 grams/dL, plasma EPO levels increase logarithmically in inverse proportion to the severity of the anemia
potential gross indicators of anemia
pale palmar crease
pale conjunctiva
But really, anemia is a laboratory finding!
Anemia
a reduction of the total circulating red cell mass below normal limits
Anemic:
An adjective which describes the clinical findings in chronic RBC deficiency:
Lacking force, vitality or spirit; insipid; lacking substance
Signs/Symptoms: pale, peaked, low energy, easily fatigued
Anemia is NOT a Disease, Syndrome, or Specific Diagnosis
Anemia is a clinical laboratory finding of a decrease in overall red cell mass when compared to others of the same age and gender and living in the same geographic location
what does anemia lead to?
decreases oxygen carrying capacity –> tissue hypoxia
three types of anemia
blood loss (majority) impaired production (diiminished) hemolytic
clinical findings with anemia
Patients appear pale. Weakness, malaise, and easy fatigability are common complaints. The lowered oxygen content of the circulating blood leads to dyspnea on mild exertion.
Hypoxia can cause fatty change in the liver, myocardium, and kidney
myocardial hypoxia manifests as
angina pectoris, particularly when complicated by pre-existing coronary artery disease.
renal results from anemia
With acute blood loss and shock, oliguria and anuria can develop as a result of renal hypoperfusion.
CNS results from anemia
Central nervous system hypoxia can cause headache, dimness of vision,* and faintness*.
Hematopoiesis
The bone marrow when stressed (and *with adequate nutrients such as sufficient iron) *can increase red cell production 4-5 fold within 7 to 10 days
Hematopoiesis normally occurs primarily in “red marrow”: medullary cavity of “flat” bones (skull, sternum, ileum) in adults
In exceptional circumstances, hematopoiesis occurs in liver, spleen or lymph nodes and then is known as “Extramedullary Hematopoiesis”
normal ratio of fat to bone marrow
50/50
2 types of blood loss
acute and chronic
acute blood loss– what do we see
Hypovolemic shock
Normochromic/normocytic
Erythropoietin levels? NORMAL!
how much blood loss is ok (acute)
10% :)
20% not so great
30% bad
Acute (Rapid) Loss RBCs
Vascular volume in a 150 pound adult is 5,000 mL whole blood – 10 “Units” of RBCs
Adult humans can tolerate loss 5-10% red cell volume in 15 minutes with few symptoms
10-15% volume loss in under 1 hour may cause symptoms:
- Rapid pulse
- Increased respirations
- Shortness of breath, particularly with effort and “lightheaded”
All symptoms and signs primarily due to *defect in vascular volume and not because of lack of O2-carrying capacity.
20% or more loss in less than an hour: evidence of vascular “shock”, postural hypotension
30% or more in an hour: profound shock with confusion, air hunger, and hypotension
what happens to white blood count in acute blood loss?
increased release from marrow
what happens to platelet count in acute blood loss?
increased release
what happens to reticulocyte count in acute blood loss?
stays normal
Chronic blood loss induces anemia when?
only when the rate of loss exceeds the regenerative capacity of the marrow or when iron reserves are depleted and iron deficiency anemia appears
rates of blood loss and bone marrow increase
Slow RBC loss: Remember: We normally “lose” 1% per day & bone marrow can increase production 4-5 fold.
1% times 5,000 mL = 50 ml per day
4% times 5,000 mL = 200 ml per day
Signs/Symptoms in Chronic RBC Loss/Deficiency - when are we symptomatic?
Most adults are not clinically symptomatic (increased pulse, increased respiration, easy fatigue with effort) until hemoglobin is <7
