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Hematology > Day 3 > Flashcards

Day 3 Flashcards

1
Q

The hemoglobin molecule is composed of what two molecules?

A

Heme(iron) and Globin(protein)

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2
Q

What element is required for hemoglobin to be capable of carrying oxygen?

A

Iron

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3
Q

In what state is CO2 carried from tissues cells to the lungs?

A

Bicarbonate

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4
Q

What percentage of the RBC mass is hemoglobin?

A

28%

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5
Q

What is the globin to heme ration in RBCs

A

1 globin : 4 heme

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6
Q

What is the composition of the globin molecule?

A

2 pairs polypeptide chains
2 alpha chains-141 amino acids
2 Beta chains- 146 amino acids

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7
Q

What is the composition of the heme molecule?

A

4 protoporphyrins w/ one Fe++(ferrous) atom

Fe++ binds reversibly with O2 or CO2

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8
Q

TRUE OR FALSE

Fe ++(ferrous ) atom can bind reversibly with oxygen and carbon dioxide

A

True

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9
Q

List the normal and abnormal hemoglobin variants

A 
Normal
-A
-F
Abnormal 
-S
-C
-D
-E
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10
Q

Define hemoglobinopathy and what causes it.

A

A disorder in which the presence of abnormal hemoglobin causes a pathological condition;

may be inherited, may be caused by genetic mutation

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11
Q

What percentage of normal adult hemoglobin is Hgb A and Hgb F

A

A-95%

F-5%

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12
Q

What Hgb variant has a greater affinity for oxygen and is the most efficient for carrying oxygen?

A

Hemoglobin F

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13
Q

At what age does Hgb F drop below 5% of all circulating hemoglobin?

A

By 2 years of age

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14
Q

Which Hgb variant Causes sickle cell anemia, and what population is almost executively at risk?

A

Hemoglobin S; African American population

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15
Q

The Hgb S variant has the ________ amino acid in place of glutamic acid on the ________ chain.

A

Valine; beta

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16
Q

What Hgb variant causes chronic hemolytic anemia and in what region is it frequently seen ?

A

Hemoglobin C ****

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17
Q

The Hgb _____ variant has the lysine amino acid in place of the glutamic acid on the _______ chain.

A

C; beta

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18
Q

Which Hgb variant is thought to protect against Plasmodium falciparum infection?

A

Hemoglobin E

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19
Q

Name the normal and abnormal hemoglobin derivatives.

A 
Normal
-oxyhemoglobin 
-reduced hemoglobin 
Abnormal 
-carboxyhemoglobin 
-methemoglobin 
-sulfhemoglobin
-cyanmethemoglobin
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20
Q

Which Hgb derivative is produced when oxygen is dissociated from iron and replaced by CO2?

A

Reduced Hemoglobin

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21
Q

Name two conditions that can occur if sufficient quantities of abnormal Hgb derivatives are circulating in the blood

A

Hypoxia- lack of oxygen

Cyanosis- bluish discoloration of skin

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22
Q

Which Hgb derivative has 200 times greater affinity for oxygen and can cause carbon monoxide poisoning?

A

Carboxyhemoglobin

23
Q

At what level does carboxyhemoglobin cause asphyxiation?

A

Levels 50-70%

24
Q

Which Hgb derivative has iron been oxidized from the ferrous to ferric state which renders Hgb incapable of combining reversibly with oxygen?

A

Methemoglobin

25
Q

What causes methemoglobin production?

A

Certain chemicals, drugs or can be inherited

26
Q

TRUE OR FALSE

Methemoglobin CANNOT be reversed back to normal hemoglobin.

A

False, can

27
Q

Which Hgb derivative causes an irreversible condition that renders the RBC incapable of transporting oxygen?

A

Sulfhemoglobin

28
Q

What is thought to cause sulfhemoglobin?

A

Drugs and chemicals such as sulfonamides

29
Q

All hemoglobin except sulfhemoglobin can be converted to which other hemoglobin derivative?

A

Cyanmethemoglobin

30
Q

What effect does altitude have on hemoglobin?

A

Normal hemoglobin concentration is higher at higher altitudes

31
Q

What is the normal hemoglobin value for females?

A

12.5- 15.3 g/dl

32
Q

List the three methods of hemoglobin measurement.

A

Specific Gravity/ Electrophoresis/ Cyanmethmeglobin Method

33
Q

What solution is used in the specific gravity method for Hgb measurement?

A

Copper sulfate method

34
Q

In the specific gravity method for Hgb measurement, what will happen to the blood drop if the specific gravity/ Hgb concentration is increased?

A

It will sink in 15 seconds

35
Q

What is the added value of Hgb electrophoresis measurement versus other hgb measurement methods?

A

Permits separation, identification and quantitation

36
Q

What is the principle of the Cyanmethmeglobin method for Hgb measurement?

A

Modified Drabkins reagent converts hemoglobin to hemiglobincyanide(HiCN) , a stable pigment

37
Q

What is the composition of Drabkins reagent ?

A

Potassium Cyanide, Potassium Ferricyanide & dihydrogen potassium phosphate

38
Q

At what wavelength does the Cyanmethmeglobin method measure Hgb?

A

540nm

39
Q

What is the Hemocue?

A

Self contained point of care analyzer which measures only hemoglobin

40
Q

How soon can the Hemocue provide results?

A

45 seconds

41
Q

How often is the Hemocue calibrated?

A

Daily

42
Q

How often must controls for Hgb determinations be accomplished?

A

Daily or follow manufacturers recommendations

43
Q

What are some sources of error for Hgb measurements?

A
  • Reagent deterioration
  • Turbidity from high WBC counts
  • Bloods/ carbon monoxide(requires several hrs to form Cyanmethmeglobin)
  • capillary sample= collection device filled completely and free of clots
44
Q

What does Hematocrit represent?

A

The volume of RBCs in a given volume of blood; % volume PRBCs

45
Q

How is a patient’s oxygen carrying capacity assessed?

A

Hematocrit correlated w/ Hemoglobin level

46
Q

What is the “rule of three” with regards to Hgb and Hct and when can it be applied?

A

Hematocrit should be approximately 3x the hemoglobin level

47
Q

What are three layers blood settles into after centrifugation?

A

Plasma(top)
Buffy coat-WBCs & platelets (middle)
RBCs(bottom)

48
Q

TRUE OR FALSE

Spun Hematocrit determinations are run in duplicate.

A

True

49
Q

In the spun hematocrit method, explain the capillary tube anticoagulant requirements for capillary punctures and traditional collection in EDTA.

A

Use heparnized capillary tubes for capillary punctures

Use plain capillary tubes to perform spun HCT on blood collected in EDTA

50
Q

Spun hematocrit samples are centrifuged at what RPM setting?

A

10,000 RPM

51
Q

What special consideration must be made when reporting automated Hct values?

A

Automated HCT values are usually lower than the values obtained w/ the spun hematocrit method.

52
Q

What are the sources of error for Hct determinations?

A

EDTA anticoagulated blood must be tested within 6hours of collection
Blood must not be clotted

53
Q

What is the normal Hct value for males?

A

40-54%

Hematology (6 decks)

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