HgB & Hct Flashcards
Also known as Respiratory Pigment
Hemoglobin
One of the tests used to diagnose and follow the treatments of anemia.
Hemoglobin
What is the main component of hemoglobin?
Red blood cells (95%)
In what state does iron bind to oxygen?
Ferrous state or Fe2+
The portion that determines the type of
hemoglobin
Globin
How many subunits does each Hgb have?
4 heme & 4 globin
1 heme is capable of carrying how many moles of O2?
1 mole
2 alpha chains/2 beta chains
Hemoglobin A
2 alpha chains/2 delta chains
Hemoglobin A2
2 alpha chains and 2 gamma chains
Hemoglobin F (1-2%)
This is coded by Chromosome 16
Alpha chain
Gamma, delta, and beta chains are coded by?
Chromosome 11
Types of Abnormal Hemoglobin
Hemoglobin S
Hemoglobin C
Hemoglobin E
Hemoglobin D
Hemoglobin G
Hemoglobin Lepore
Hemoglobin whose structures have been modified due to drugs or environmental chemicals
Hemoglobin variants/ Abnormal Hemoglobin Pigmentation/ Dyshemoglobin
Can cause increased O2 affinity thus decreasing the efficiency of Oxygen to be delivered to the tissues
Methemoglobin
Methemoglobin is caused by?
oxidants (Nitrite, Primaquine,
dapsone, Benzocaine) or Methemoglobin Reductase deficiency
Methemoglobin can be treated by
administration of Ascorbic Acid and Methylene Blue
Sulfhemoglobin is caused by?
sulfonamides, phenacetin, nitrites,
phenylhydrazine
Addition of Hydrogen sulfide to the hemoglobin (greenish pigment) causes
Sulfhemoglobin
The only irreversible Abnormal hemoglobin pigmentation
Sulfhemoglobin
Caused by the combination of heme and carbon monoxide
Carboxyhemoglobin
CO has an affinity to hemoglobin of ____ than that of oxygen
240x
Carboxyhemoglobin can be treated by
Oxygen Saturation or
Hyperbaric oxygen therapy
This is the reference method approved by the Clinical and Laboratory Standards Institute for Hemoglobin determination.
The cyanmethemoglobin (hemoglobincyanide) method
Principle of cyanmethemoglobin (hemoglobincyanide) method
In the cyanmethemoglobin method, blood is diluted in an alkaline Drabkin solution of potassium ferricyanide, potassium cyanide, sodium bicarbonate, and a surfactant.
The absorbance of the cyanmethemoglobin is at _____
540 nm
The absorbance of the cyanmethemoglobin at 540 nm is
directly proportional to?
hemoglobin concentration
This cannot be converted to cyanmethemoglobin; it cannot be
measured.
Sulfhemoglobin
This is the instrument used for Hemoglobin determination
Spectrophotometer
The reagent used in Hemoglobin determination
Detergent-modified Drabkin’s reagent.
Components of Drabkin’s reagent
Potassium Cyanide
Potassium Ferricyanide
Potassium dihydrogen phosphate or sodium bicarbonate
Non-ionic compound (improves cell lysis)
Potassium ferricyanide:
hemoglobin → methemoglobin
Potassium cyanide:
methemoglobin → cyanmethemoglobin
The anticoagulant used for Hgb determination
EDTA or Heparin
These are resistant to hemolysis, causing turbidity
Cells containing Hb S and Hb C
This hemoglobin takes 1 hour to convert to cyanmethemoglobin and theoretically could cause erroneous results in samples from heavy smokers
Carboxyhemoglobin
Why do need to be cautious with the hemoglobin reagent?
Because it contains cyanide, which is
highly toxic. Acidification of cyanide in the reagent releases highly toxic hydrogen cyanide gas
The ratio for reagent to blood in Hgb determination
5 ml or 5000 ul of reagent, 20 ul or 0.02 ml of whole blood.
Normal Hemoglobin values
Male: 14-18 g/dL
Female: 12-15 g/dL
Newborn: 16.5-21.5 g/dL
Technical sources of errors for Hgb determination
Pipetting errors
Dirty and scratch cuvettes
Deteriorated reagent
Biologic sources of errors for Hgb determination
Lipemic Sample
Leukocytosis
Hgb S and Hgb C
Refers to the volume of packed red blood cells that occupy a given volume of whole blood.
Hematocrit
Hematocrit is often referred
to as
packed cell volume (PCV)
It is reported either as a percentage (e.g., 36%) or in liters per liter (0.36 L/L).
Hematocrit
Anticoagulant used for microhematocrit
EDTA or heparin
Two methods for hematocrit testing
Macrohematocrit (uses wintrobe tube)
Microhematocrit (uses capillary tube)
Normal Hematocrit values
- Male 40-54% (0.40-0.54 L/L)
- Female 35-49% (0.35-0.49 L/L)
- Newborn 53-65% (0.53-0.65 L/L)
- Child 30-43% (0.30-0.43 L/L)
The instrument used to determine hematocrit
microhematocrit reader
What are the four layers in a hematocrit tube?
Plasma, buffy coat (WBCs & platelets), and RBCs
The length of the sealing clay
at least 4 mm long
When loading the micro hematocrit centrifuge, the clay ends must be facing the _____ from the center, touching
the rubber gasket
outside away
How many minutes should you centrifuge the capillary tubes?
Centrifuge the tubes for 5 minutes between the speed of 10,000 g to 15,000 g
Factors that cause a false decrease in hematocrit
-Incomplete sealing of tubes
-Hemolysis
-Over Anticoagulated Blood
-Introduction of interstitial fluid from a skin puncture or the improper flushing of an intravenous catheter
Factors that cause a false increase in hematocrit
-Reading including the buffy coat
-Inadequate centrifugation
-Abnormal RBC Morphology: Macrocytic -Anemia, Spherocytosis, Thalassemia, Hypochromic Anemia, Sickle Cell Anemia
-Fluid loss associated with dehydration
