Lecture 3 Flashcards

(17 cards)

1
Q

Hematocrit

A

Hct: is also called packed cell volume or PCV.
Percentage of RBC in whole blood
Red band - heparin
Blue band no anti ..use for EDTA blood
• Micro hematocrit is the volume of RBCs after centrifuging of whole blood for 5 min at 12,000 rpm.
• Comprises RBCs that are normally 40-50% of blood volume
• Requires a small volume of blood
• Reported in L/L (SI units)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Specimen Hematocrit

A
  • Purple (lavender top EDTA ) Venous blood
  • or capillary blood collected directly into heparinized capillary tubes - only fill 3/4 of the tube
  • Specimens should be centrifuged within 4 hours of collection.
  • Hemolyzed samples cannot be used for testing (if the red cells are hemo lyzed we will have less RBC because theyll be ruptured)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Normal Values Hematocrit

A

infant 0.50 - 0.60
toddler ~ 0.35-0.42
male 0.40 - 0.50
female 0.35 - 0.50

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Critical Values:

Manual Measurement

A

<0.20 and > 0.60

SPUN or MICRO HEMATOCRIT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Reading the Hematocrit Value

A

Hct = height (volume) of RBCs compared to the height (total volume of blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Rule of Three

A

Hemoglobin X 3= Hematocrit +/-3

Hb 120 x0.03 = 360 g/L
360/1000
Hct 0.36 L/L (+/-0.03)
Note: do not include the buffy coat in the hematocrit reading as this falsely elevate the results

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Automated (Electronic) Hct Measurement (CALCULATED HEMATOCRIT

A
  • –provide an indirect measurement of hematocrit
    • – number of RBCs and mean cell volume (MCV-fL) are measured
  --- Hct is calculated using formula:  
Hct = RBC X MCV  
 #cells X mean cell volume

MCHC, mean cell haemoglobin concentration (mmol/L) =Hb/Hct
MCHC (g/L) is the average concentration of Hb in the each RBC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

trapped plasma.

A
  • When the microhematocrit is spun a small amount of plasma remains in the red blood cell portion
  • Comparison of spun microhematocrit results with hematocrit results obtained from an electronic cell counter, the spun hematocrit results are generally 1.% to 3% higher due to this trapped plasma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

RBC with normal Hb - is like what

A

Cell is normochromic (normal size and normal color)
Hb/Hct ~ 350
MCHC is normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

RBC of same volume but less Hb - is like what

A

Cell is hypochromic (pale)
Hb /Hct < 300
MCHC is low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Quality control for hematocrit machine

A

 Perform test in duplicate; results should be within ±0.01(± 2%)
 run commercially prepared controls on automated instrument
 check centrifuge speed and timer
 proper collection of blood sample (uniform distribution, no hemolysis, no microclots)
 Commercially prepared controls are available for spun hematocrit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Sources of Error for hematocrit

A
  • Improper sealing of the capillary tube- ↓ due to loss of RBC’s – the blood comes out of the tube and into the centrifuge
  • Increase concentration of anticoagulant – ↓ due to underfilled tube- the ratio of blood to anticoagulant is not proper
  • Improper mixing of blood-↓ or ↑
  • Time and speed of centrifuge- ↑ due to trapped plasma
  • Improper collection of specimen- ↑or ↓
  • Hemolysis -↓lysing of RBC’s
  • Delay in reading- ↑due to unpacking of RBC’s – if you don’t read right after centrifuge they will start to unpack
  • Abnormal RBC morphology due to trapped plasma – fragmented, sickle cell will trap in the plasma
  • Buffy coat included-↑
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Clinical Significance Hematocrit

A

Clinical Significance Hematocrit is a measurement of the fractional volume of red blood cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Increased hematocrit

A
  • • Increase dehydration-↓ plasma volume and falsely ↑the hematocrit reading. Lots of RBC but less plasma
  • EPO stimulation-increased – drug given to patient with cancer that cant produce RBC. Made in the liver
  • residence at high altitude-increased. Lungs produce more hemo so RBC can carry more oxygen – higher hematocrit –more RBC
  • Diuretic therapy – release of water so less plasma volume more RBC
  • burns – no more plasma so increase of RBC
  • an increase in red blood cells, such as in cardiovascular and renal disorders, polycythemia vera, and impaired ventilation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Decreased hematocrit

A
  • Bleeding-decreased
  • Overhydration, which increases the plasma volume,
  • problems with RBC production (sickle cell, amemias, thalasemisa, spherocytosis, bleeding)-decreased
  • macrocytic anemias, spherocytosis, thalassemia, hypochromic anemias, and sickle cell anemia-increased trapped plasma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Lab Safety for hematocrit

A

Standard Precautions
Safe use of centrifuge
Use plastic capillaries

17
Q

Buffy Coat Prep

A

EDTA blood is centrifuged in a Wintrobe tube or lavender top EDTA blood tube

  • WBCs are concentrated between the plasma and RBCs
  • Buffy Coat is removed by using a long tipped pasture pipette
  • Make 2 smears
  • Stain with Wright’s
  • Used for differential when WBC is low (under 3.0x 109/L)