Erythropoiesis

Question 1

Where to red blood cells come from?

Answer 1

blood stem cell–> myeloid stem cell–> RBC

Question 2

Red Blood Cell (RBC) Function

Answer 2

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.

Question 3

RBC lifespan.

What happens to them as they age?

Answer 3

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).

Question 4

Regulation RBC Production

Answer 4

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

Question 5

potential gross indicators of anemia

Answer 5

pale palmar crease
pale conjunctiva

But really, anemia is a laboratory finding!

Question 6

Anemia

Answer 6

a reduction of the total circulating red cell mass below normal limits

Question 7

Anemic:

Answer 7

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

Question 8

what does anemia lead to?

Answer 8

decreases oxygen carrying capacity –> tissue hypoxia

Question 9

three types of anemia

Answer 9

blood loss (majority)
impaired production (diiminished)
hemolytic

Question 10

clinical findings with anemia

Answer 10

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

Question 11

myocardial hypoxia manifests as

Answer 11

angina pectoris, particularly when complicated by pre-existing coronary artery disease.

Question 12

renal results from anemia

Answer 12

With acute blood loss and shock, oliguria and anuria can develop as a result of renal hypoperfusion.

Question 13

CNS results from anemia

Answer 13

Central nervous system hypoxia can cause headache, dimness of vision,* and faintness*.

Question 14

Hematopoiesis

Answer 14

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”

Question 15

normal ratio of fat to bone marrow

Answer 15

50/50

Question 16

2 types of blood loss

Answer 16

acute and chronic

Question 17

acute blood loss– what do we see

Answer 17

Hypovolemic shock
Normochromic/normocytic
Erythropoietin levels? NORMAL!

Question 18

how much blood loss is ok (acute)

Answer 18

10% :)
20% not so great
30% bad

Question 19

Acute (Rapid) Loss RBCs

Answer 19

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

Question 20

what happens to white blood count in acute blood loss?

Answer 20

increased release from marrow

Question 21

what happens to platelet count in acute blood loss?

Answer 21

increased release

Question 22

what happens to reticulocyte count in acute blood loss?

Answer 22

stays normal

Question 23

Chronic blood loss induces anemia when?

Answer 23

only when the rate of loss exceeds the regenerative capacity of the marrow or when iron reserves are depleted and iron deficiency anemia appears

Question 24

rates of blood loss and bone marrow increase

Answer 24

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

Question 25

Signs/Symptoms in Chronic RBC Loss/Deficiency - when are we symptomatic?

Answer 25

Most adults are not clinically symptomatic (increased pulse, increased respiration, easy fatigue with effort) until hemoglobin is <7