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Questions and Answers
A researcher is studying a population in a high-altitude environment. How would you expect the hematocrit levels of this population to compare to a population at sea level, and why?
A researcher is studying a population in a high-altitude environment. How would you expect the hematocrit levels of this population to compare to a population at sea level, and why?
- The same, as altitude does not significantly impact hematocrit levels.
- Lower, due to decreased oxygen availability stimulating red blood cell production.
- Lower, due to increased plasma volume diluting the red blood cell concentration.
- Higher, as a physiological response to lower oxygen availability. (correct)
During a blood donation drive, a potential donor is rejected due to a low hematocrit level. What condition might this indicate, and how does it affect the oxygen-carrying capacity of the blood?
During a blood donation drive, a potential donor is rejected due to a low hematocrit level. What condition might this indicate, and how does it affect the oxygen-carrying capacity of the blood?
- Dehydration; reduces the oxygen-carrying capacity.
- Anemia; reduces the oxygen-carrying capacity. (correct)
- Polycythemia; increases the oxygen-carrying capacity.
- Overhydration; increases the oxygen-carrying capacity.
A patient's hematocrit is measured using a micro-centrifuge method. After centrifugation, the packed red blood cell level is not clearly distinguishable due to potential user error. Which step would be MOST crucial to repeat to ensure accuracy?
A patient's hematocrit is measured using a micro-centrifuge method. After centrifugation, the packed red blood cell level is not clearly distinguishable due to potential user error. Which step would be MOST crucial to repeat to ensure accuracy?
- Sterilizing the thumb with alcohol.
- Centrifuging the tube at the correct speed and time. (correct)
- Filling the capillary tube with oozing blood.
- Sealing one end of the capillary tube with wax.
If a lab technician consistently obtains lower-than-expected hematocrit readings, what is the most likely source of procedural error in their technique?
If a lab technician consistently obtains lower-than-expected hematocrit readings, what is the most likely source of procedural error in their technique?
A newborn's hematocrit level is found to be 58%. How does this compare to typical adult values, and what is the primary physiological reason for this difference?
A newborn's hematocrit level is found to be 58%. How does this compare to typical adult values, and what is the primary physiological reason for this difference?
A patient experiencing chronic dehydration is likely to have a hematocrit level that is:
A patient experiencing chronic dehydration is likely to have a hematocrit level that is:
If a patient's hematocrit is significantly lower than the normal range, but their red blood cell count is normal, which condition is MOST likely contributing to this discrepancy?
If a patient's hematocrit is significantly lower than the normal range, but their red blood cell count is normal, which condition is MOST likely contributing to this discrepancy?
In a micro-hematocrit test, what would be the MOST likely consequence of failing to properly seal the capillary tube before centrifugation?
In a micro-hematocrit test, what would be the MOST likely consequence of failing to properly seal the capillary tube before centrifugation?
Why might an athlete training at high altitude experience an elevated hematocrit level, and what is the underlying physiological mechanism?
Why might an athlete training at high altitude experience an elevated hematocrit level, and what is the underlying physiological mechanism?
How would you expect the hematocrit levels of a woman to change during her menstrual cycle, and what is the primary reason for this?
How would you expect the hematocrit levels of a woman to change during her menstrual cycle, and what is the primary reason for this?
Flashcards
Hematocrit (HCT)
Hematocrit (HCT)
The percent ratio of red blood cell volume to total blood volume.
Packed Cell Volume (PCV)
Packed Cell Volume (PCV)
Volume of blood that consists of red blood cells.
Normal Hematocrit Values
Normal Hematocrit Values
Males: 44-54%, Females: 37-47%, Newborns: 55-60%
Factors Affecting Hematocrit
Factors Affecting Hematocrit
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Decreased Hematocrit (!Hct)
Decreased Hematocrit (!Hct)
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Study Notes
- Hematocrit (HCT) is also known as packed cell volume (PCV).
- Whole blood consists of plasma (55%), WBCs and platelets (<1%), and erythrocytes (45%).
- Components of whole blood are called “formed elements”
Definition of Hematocrit
- Hematocrit is the percent ratio of red cell volume to total blood volume.
- Hct = (RBCs volume / Total blood volume) x 100
Normal Hematocrit Values
- Male: 44-54%
- Female: 37-47%; males have higher Hct due to testosterone, which is not present in females during menstruation.
- Newborn: 55-60%, due to relative hypoxia.
Factors Affecting Hematocrit Value
- Number of RBCs
- Volume of Plasma
Physiological Factors
- Age: Hematocrit is high in newborns
- Sex: Hematocrit is higher in males than females
- High Altitude: relative hypoxia
Pathological Factors
- Lowered Hematocrit: Anemia and Overhydration
- Elevated Hematocrit: Polycythemia and Dehydration
Tools for Measuring Hematocrit
- Alcohol
- Cotton
- Sterilized Lancet
- Heparinized micro-capillary tube (red circle)
- Crista seal paste or wax
- Micro-centrifuge
- Hct scale or Hct ruler
Steps for Measuring Hematocrit
- Sterilize the thumb with alcohol, allow it to dry, then prick it with a sterilized lancet.
- Fill the capillary tube (or 3/4 of its length) with blood.
- Blood is withdrawn by capillary attraction (capillarity).
- Seal one end of the tube with wax.
- Centrifuge the tube at 3000 revolutions per minute for 3 minutes.
- The RBCs will pack together at the bottom of the tube, while plasma will remain above.
- Place the lower level of RBCs on the zero line of the Hct scale and the upper limit of clear plasma on the 100% line.
- Read the Hct directly on the scale at the upper level of RBCs.
Comment
- Normal Hct values are:
- Male: 44-54%
- Female: 37-47%
- Newborn: 55-60%.
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Description
Explore hematocrit (HCT), also known as packed cell volume (PCV), which is the percentage of red blood cells in total blood volume. Learn about normal hematocrit values for males, females, and newborns, and discover the physiological and pathological factors that can affect HCT levels.
