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113 Cards in this Set
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- Back
- 3rd side (hint)
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Hematocrit is aka ____________________.
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Packed cell volume of whole blood.
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Hematocrit
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Measurement of the ratio of volume occupied by the RBCs to the volume of the blood.
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When hematocrit level I being performed, what is the key step after drawing blood into capillary tube?
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Sample is centrifuged and the volume of packed cells is measured.
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How is the measurement of hematocrit expressed?
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As a percentage or as a decimal fraction in liters/liters. Ex: 36% is 0.36 L/L.
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Hematocrit is useful in diagnosing what medical conditions?
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Anemia, polycythemia, hemodilution, or hemoconcentration.
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What do automated methods not measure?
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Packed cell volume.
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What is hematocrit calculated from?
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From the RBC number and size.
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How much percentage is manual hematocrit higher than automated methods?
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2%.
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Specimens are collected in what tubes? (Hematocrit)
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EDTA or capillary blood directly into heparinized capillary tubes.
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Blue banded tubes contain what?
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No anticoagulant.
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Red banded tubes contain what?
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Heparin.
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What layers are seen in capillary tube after centrifuged?
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Clay sealant, red cells, Buffy coat (wbc and platelets), and plasma.
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Do you include the Buffy coat when reading hematocrit level?
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No.
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Which cells are heaviest?
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RBC.
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Reference range of hematocrit.
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Males: 40-55%
Females: 35-45%. |
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What hormone causes changes in hematocrit?
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Testosterone.
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Reasons for decreased HCT.
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Anemia, evening, laying down, low altitude, and acute blood loss.
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Reasons for increased HCT.
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Polycythemia, morning, burns, dehydration, strenuous activity, and increases altitude.
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Procedure for performing manual microhematocrit.
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1. Mix blood thoroughly.
2. Draw blood into microhematocrit tubes by capillary action. Should be filled about 3 or 4ths of their lengths. 3. Wipe with chemwipe. 4. Seal one end with clay. Hold horizontally and sealant vertically. Hold close to end nearest sealant to prevent breakage. 5. Place in centrifuge with sealed end to outside. Make sure there's a balance tube. 6. Secure centrifuge. 7. Set timer for 5 minutes. Speed should be between 10,000 and 15,000 rpm. 8. Remove and read PCV. |
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How is a manual hematocrit measured?
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Adjust the top of clay sealant to the 0 mark and top of plasma to 100. The line that intersects with the top of the RBC is read. Buffy coat not included. Tubes shouldn't be in centrifuge for more than 10 minutes because the interface between the plasma and cells will become slanted and an inaccurate reading will result.
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Main component of RBC.
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Hemoglobin.
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Purpose of hemoglobin.
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Transports co2 and oxygen.
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How much oxygen does each gram of hemoglobin hold when fully saturated?
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1.34 mL of oxygen.
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How much hemoglobin does the red cell mass of adult contain?
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Approx 600 grams and capable of carrying 800 mL of oxygen.
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What does a molecule of hemoglobin consist of?
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2 pairs of polypeptide chains (globin) and 4 prosthetic heme groups which each contain one atom of ferrous iron.
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What binds with O2? (Hemoglobin)
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Iron.
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The two most commonly known globins.
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Hemoglobin and myoglobin.
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Neuroglobin.
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Discovered in 2003 in human brain tissue.
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Name of globin found in all body cells.
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Cytoglobin or histoglobin.
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Main function of hemoglobin.
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Transport oxygen from the lungs where oxygen tension is high to tissues where it is low.
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At oxygen tension of 100mm Hg in lungs, how much hemoglobin is combined with oxygen?
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95-98%.
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How low can oxygen tension be in tissues?
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20 mm Hg.
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What can happen to oxygen in tissues?
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Can readily dissociate from hemoglobin.
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If oxygen dissociates from hemoglobin, what percentage remains attached to hemoglobin?
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30%.
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Terms for the two types of physiologic hemoglobins.
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Oxyhemoglobin and deoxyhemoglobin aka reduced hemoglobin.
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Oxyhemoglobin
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Hgb + O2.
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Deoxyhemoglobin
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Hgb - O2 + co2. Aka reduced hemoglobin.
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Where does heme synthesis occur?
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Most cells except mature RBCs.
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Heme synthesis is most abundant where?
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Erythroid precursors.
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What is heme formed from and where does the process begin?
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Porphyrins, mitochondria.
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Next steps of heme formation occurs where?
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Cytoplasm.
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Where do the final steps of heme formation occur?
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Back within the mitochondria.
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Where does globin synthesis occur?
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Cytoplasm of all RBCs other than mature red cells.
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% of heme and globin.
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6% heme, 94% globin.
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How is hemoglobin synthesis primarily controlled?
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Through the action of heme.
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What inhibits further heme synthesis as well as promotes it?
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Increased heme.
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What hormone promotes hemoglobin synthesis?
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Erythropoietin.
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Where is erythropoietin produced?
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Peritubular cells of kidneys and Kupffer cells of liver. 85-90% in kidneys, 10-15% in liver.
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Iron is delivered to the hemoglobin producing cells via _________.
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Transferrin.
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What does excess iron accumulate as?
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Ferritin aggregates in cytoplasm of immature cells if hemoglobin production isn't balanced with iron.
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What stain is used for iron granules?
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Prussian blue.
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What are cells that accumulate excess iron called?
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Sideroblasts.
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Gower 1.
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2 zeta, 2 epsilon.
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Gower 2
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2 alpha, 2 epsilon.
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Portland 1
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2 zeta, 2 gamma.
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Hemoglobin F (fetal)
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2 alpha, 2 gamma.
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Hemoglobin A
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2 alpha, 2 beta.
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Hemoglobin A2
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2 alpha, 2 delta.
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What are embryonic hemoglobins formed by?
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Immature erythrocytes in yolk sac.
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Where are embryonic hemoglobins found?
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In the human embryo until about 3 months of gestation.
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Predominant hemoglobin found in the fetus.
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Fetal hemoglobin.
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When does fetal hemoglobin first appear?
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At the fifth week of gestation and persists for several months after birth.
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What is embryonic hemoglobin associated with?
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Hepatic erythropoiesis.
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When does bone marrow erythropoiesis begin?
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4th month of gestation, but doesn't become primary hematopoietic organ until the end of the 5th of 6th month of gestation.
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When does the synthesis of adult type hemoglobin begin?
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During fetal development, but slow until the week's proceeding birth.
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What % of total hemoglobin is HgbF at birth?
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60-80%.
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At what age does normal adult hemoglobin replace HgbF?
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Approx 6 months.
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How much HgbF does an adult have in circulation?
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2%.
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What kind of hemoglobin is the majority in adults?
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Hemoglobin A. 95-97%.
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How much of hemoglobin does HgbA2 account for?
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2.5%.
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Approximately 5% of HgbA undergoes _______________________.
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Posttransitional glycosolation.
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Approximately 5%
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What does posttransitional glycosolation result in?
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Linkage of sugars to serine, asparagine, and hydroxylysine residues.
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The glycosolated hemoglobins
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A1A (less than 1%) A1B (less than 2%) A1C (3%).
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After making protein, hemoglobin can be ____________.
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Glycosolated. Glucose becomes attached.
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Which hemoglobin is associated with diabetes?
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A1C.
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Glycosolation of hemoglobin increases in a ______ fashion over the ____ day lifespan of RBCs.
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Linear, 120.
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What is measurement of A1C a good indication of?
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Time averaged (2-3 months) glucose concentration of diabetic patient.
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Carboxyhemoglobin
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Hgb + Carbon monoxide.
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What happens once Carboxyhemoglobin is formed?
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Extremely stable and unable to easily bind with and carry oxygen.
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What happens when Carboxyhemoglobin is unable to bind to oxygen?
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Tissue hypoxia.
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How much HgbCO do normal humans have in bloodstream and why?
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0.5%; natural degradation of hemoglobin.
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Slightly increased HgbCO is found in what conditions?
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Smokers and hemolytic anemias.
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What % of HgbCO can cause problems and what does it cause?
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20-30%; dizziness, nausea, headache, and muscular weakness.
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Acute HgbCO poisoning.
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More than 40% can quickly lead to death.
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Possible exposure of carbon monoxide.
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Gas motors, gas heaters, defective home heating units, and traffic jams.
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Why is treatment for co2 treatable and how?
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Because the bond between hemoglobin and carbon monoxide is reversible; treated with hyperbaric chamber which forces gas back into cells.
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What color does Carboxyhemoglobin cause blood to be?
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Bright cherry red, victims display bright red faces.
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How is quantitation of HgbCO made?
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With differential spectrophotometry and gas chromatography.
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What happens to the iron atom in methemoglobin?
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It is oxidized to the ferric state. (Fe+3)
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What state must iron be in to reversible bind with oxygen?
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Ferrous state. (Fe+2)
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______ iron is incapable of binding with oxygen.
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Ferric.
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How much methemoglobin is typically in the bloodstream at all times?
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2%.
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What is methemoglobin reduced by?
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Enzyme systems.
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What % of methemoglobin can cause humans to become cyanotic?
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10%.
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Cause of methemoglobinemia.
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Increased production of HI or decreased NADH-cytochrome b5 reductase activity. May be hereditary or acquired.
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Hemoglobin M disorders.
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Various forms of genetic alterations produce an asymptomatic cyanosis.
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What can increased HI be caused by?
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Environmental exposure or certain oxidizing drugs.
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Why are infants more susceptible to HI?
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Because HgbF is more easily converted to HI and because infants RBCs are often deficient in enzymes necessary to break down HI.
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What color does methemoglobin make blood?
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Chocolate brown.
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When is sulfhemoglobin formed?
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When hemoglobin is bound to sulfur.
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What does oxidation of sulfhemoglobin lead to the formation of?
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The formation of Heinz bodies in the RBCs.
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What can sulfhemoglobin combine with?
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It can't transport oxygen, but it can combine with CO to form carboxysulfhemoglobin.
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Can sulfhemoglobin be reduced back to hemoglobin?
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No. It remains in cells until they are broken down.
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What color does sulfhemoglobin give blood?
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Mauve lavender color. Cannot be measured with routine methods.
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Cyanmethmoglobin: what is blood diluted in?
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Drabkin's reagent which is a solution of potassium ferricyanide and potassium cyanide.
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The ferrous ions are oxidized with what? (Cyanmethemoglobin)
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Oxidized to the ferric state by potassium ferricyanide to form methemoglobin.
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What happens once methemoglobin is formed?
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It reacts with the cyanide ions provided by potassium cyanide to form cyanmethemoglobin which is a stable colored solution.
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How is the amount of cyanmethemoglobin measured?
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Spectrophotometrically and compared to known hemoglobin standards in order to determine the hemoglobin concentration of patient sample.
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Basic parts of spectrophotometer.
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Light source, wavelength selector, material being measured, photoelectric cell, amplifier, and galvanometer.
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Copper sulfate method
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Indirect measure of Hgb based on specific gravity.
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Reference ranges of hemoglobin
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Males: 13-18 g/dL
Females: 12-16 g/dL |
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What is the spectrometer based on?
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Beer's law.
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Formulas to figure hemoglobin and hematocrit.
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(3) Hgb = Hct
(9) RBC = Hct (3) RBC = Hgb |
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