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Hematocrits
The hematocrit, or packed RBC volume, is the ratio of the volume of RBC's to the volume of whole blood.
Hematocrit is usually expressed as a percentage. The hematocrit should be approximately 3 times the hemoglobin.
Microhematocrit Determination
Materials needed:
capillary tubes
hematocrit centrifuge
gauze squares
Critoseal
II. Procedure:
A. Fill capillary tubes 3/4 full of blood.
B. Wipe off excess blood with gauze square.
C. Place finger on end of tube and carefully press other end into clay to plug.
D. Spin in hematocrit centrifuge for 5 minutes at 11,000 rpms.
E. Determine volume of packed red cells, expressed as a percentage of the total volume. Do not include the buffy coat in the reading.
Normal values:
women 37-47%
men 40-54%
Note
The hematocrit is decreased in anemia and increased in polycythemia and dehydration.
Sources of Error
A. inadequate mixing of blood
B. excess anticoagulant causes RBC's to shrink, decreasing the hematocrit
C. inadequate centrifugation
D. including buffy coat in reading
The hematocrit, or packed RBC volume, is the ratio of the volume of RBC's to the volume of whole blood.
Hematocrit is usually expressed as a percentage. The hematocrit should be approximately 3 times the hemoglobin.
Microhematocrit Determination
Materials needed:
capillary tubes
hematocrit centrifuge
gauze squares
Critoseal
II. Procedure:
A. Fill capillary tubes 3/4 full of blood.
B. Wipe off excess blood with gauze square.
C. Place finger on end of tube and carefully press other end into clay to plug.
D. Spin in hematocrit centrifuge for 5 minutes at 11,000 rpms.
E. Determine volume of packed red cells, expressed as a percentage of the total volume. Do not include the buffy coat in the reading.
Normal values:
women 37-47%
men 40-54%
Note
The hematocrit is decreased in anemia and increased in polycythemia and dehydration.
Sources of Error
A. inadequate mixing of blood
B. excess anticoagulant causes RBC's to shrink, decreasing the hematocrit
C. inadequate centrifugation
D. including buffy coat in reading
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