Thursday, September 23, 2010

3.3b Red Blood Cells/Too Few or Too Many

Physician's Notebooks 3  - - See Homepage
Update 25 November 2018
(This continues Chapter 3)
3b Red Blood Cells: Too Few/Too Many - Anemia/Polycythemia

The blood consists of Red Blood Cells (RBC), White Blood Cells (WBC), platelets (thrombocytes) and plasma. The RBCs are normally about 45% by volume of a Whole Blood sample. The WBCs are normally less than 1% of all the cells; they promote the immune response and protect against infection. The platelets are cell fragments that help blood clotting and are normally less than 1% in volume in Whole Blood. The blood also has less than 1% of other cells - bone marrow precursors of the red and white cells; rarely, it may have cancer cells.

The RBC delivers usable oxygen, O2, to each cell, and removes carbon dioxide, CO2, a product of oxygen energy-generating metabolism. Each RBC is made in the bone marrow – c. 2-billion cells a day – liberated into blood, and each one functions for c.120 days before being replaced. Old RBCs, WBCs and platelets are trapped by the spleen, which acts like a filter for old or injured cells.

An RBC has the red oxygenated pigment, hemoglobin (Hgb), each molecule with an iron atom at its core. It makes a fair-skinned person's skin pinkish and all people healthy because it transfers and transports the oxygen we breathe in air, loosely connected as the oxyhemoglobin molecule, to the tissues. Blood hemoglobin level may now be easily tested for as part of the latest pulse oximeters, that lightly pinch an index finger without needling it.

After transporting O2 to tissues in the bright red blood, the hemoglobin, then attached to CO2, in the dark blood in veins, is returned back to the the right heart and then to the lungs where it gives up the CO2 by exhalation into the bronchial tubules and picks up more O2 from breathed-in air. Then the newly oxygen-containing bright red blood flows back to the left heart for another cycle.

The key red blood cell measurements are the RBC cell count per microliter, the Hemoglobin (Hgb) concentration per deciliter, and the RBC volume percentage (hematocrit, or Hct) in whole blood. These three are obtained in the complete blood count, or CBC. Each is a marker of good health, or a warning of bad health. Low RBC, Hgb or Hct is Anemia, well known as part of many diseases and a cause of skin pallor, fatigue, shortness of breath and rapid heartbeat at rest. The less frequent high RBC, Hgb or Hct is Polycythemia an early marker of low body oxygen from heart or lung disease, or a sign of early cancer (especially kidney or brain tumor), and it is a risk factor of internal blood clot that can end in stroke, heart attack or pulmonary embolus.
   The Hematocrit (Hct) is the most practical, accurate test and, to get it, a blood sample may be obtained by finger stick. A Hematocrit, for example, of 50% (High value) means half the volume of whole blood is made up of the red blood cells. The various percentages follow from that.

                   The Below Shows a Hematocrit Tube with Blood Separation

100 ------  Top of column of separated whole blood tube sample

                Upper, clear column of tube, yellow plasma
 50 …….  Top level of packed RBC's column (Hct 50%, a high value)

Here in above is the capillary tube method of doing Hematocrit. A thin tube is filled with fresh blood from fingertip prick, the tube is spun down in centrifuge and the result you see above - a lower packed column of red blood cells - read off as a hematocrit (Hct) percentage of the total column that includes the clear yellow blood plasma on top.

Healthy persons have a hematocrit between 41 and 46%. Between 35 and 40% may also be healthy although within this lower range some are anemic. At 35% or lower is anemia and its cause should be investigated. As one approaches 30% there is increasing loss of stamina and a rapid resting heart rate. From 25 to 30% is a serious anemia that needs quick correction. Below 25% needs blood transfusion. Below 20% risks imminent death.

The health consequences of anemia are related to the cause and rapidity of its development. An anemia due to acute, rapid blood loss – such as stomach hemorrhage with hematocrit drop from 45 to 40% – may be accompanied by severe collapse with very rapid heart rate and low blood pressure and must be treated as emergency. But a chronic, slowly developing anemia from leukemia can show a hematocrit as low as 25% without a patient being aware of symptom other than loss of stamina on exertion. Pallor may be a sign of anemia in fair skin.

Blood transfusion for anemia: If you are not collapsing from obvious rapid blood loss as in hemorrhage, better not to get a blood transfusion without good medical explanation. If delay is practical, seek expert second opinion. Blood transfusion has, rarely, deadly or, occasionally, chronic complications from HIV to hepatitis C.
   If one must get blood transfusions, cultivate donors who are close DNA: children, parents, siblings, first cousins and also donate your own blood to yourself a few weeks before expected need (surgery)

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