Haematocrit Flashcards
What is the definition of a haematocrit?
The number of RBC in the blood - expressed as a percentage
What is the average haematocrit of a male and female?
Males = 42% Females = 38%
How is the haematocrit measured?
By centrifuging blood in a calibrated tube (where you can directly read the percentage of cells).
Cells separate from the plasma due to their higher weight.
Without centrifugation sedimentation would still occur, just at a very slow rate.
Steps:
1) A drop of blood is taken
2) Blood is treated with an anticoagulant
3) Shake the sample
4) Fill 2/3 of a capillary with blood
5) Seal with a flame
6) Centrifuge
7) Measure result, calculate percentage
What results if the haematocrit increases?
The viscosity increases as the haematocrit increases.
Normal blood has a viscosity of 3.
Meaning that it takes 3 times as much pressure to force it though a blood vessel, in comparison to water.
If the haematocrit rises to 60-70%, the viscosity will rise to 10.
What is polycythemia?
A disease where the red blood cell count rises.
What is hypoxic hypoxia?
Due to lower O2 in the air, or an obstruction of the air ways.
What is histotoxic hypoxia?
The amount of RBC’s is normal, but there is a problem with the mitochondria or their enzymes.
What is anaemic hypoxia?
Low RBC count.
What is strangulatory hypoxia?
Decreased blood flow.
