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Clinical Chemistry Lab > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What type of specimen is used Gas analysis?

A

-Whole blood (Unclouded, unseparated) 
-arterial most common
-Venous is fine for acid-base

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2
Q

”capillary” can be considered as “arterialized”  if limb is warmed to _____ Degrees Celsius (Increases blood flow) prior to collection

A

45

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3
Q

What are four pre-analytical considerations for blood gas analysis?

A

-specimen container
-Anticoagulants
-Technique of collection
-Storage and transport

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4
Q

What specimen containers can be used?

A

-glass (best for pO2), Well Stoppared-gas tight for 2 hours
-plastic syringes (Permeable to gas)
-Capillary tubes*

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5
Q

If plastic container is used for pO2, The sample must be analyzed within ____ Minutes of being drawn

A

15*

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6
Q

 Plastic is permeable to gas (ok for pH, pCO2, HCO3-, ___________ and ___________). 

A

Base excess, electrolytes

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7
Q

What anticoagulant is used for blood gas analysis?

A

Heparin

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8
Q

 do you want to use the minimum amount of anticoagulant necessary. Otherwise how would the results be altered?

A

Decreased pH, [HCO3-], base excess, Ca2+

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9
Q

What are the two forms of heparin?

A

-dry
-Solution

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10
Q

Form of heparin that has the advantage of little dilution of specimen, disadvantage- takes time for heparin to dissolve and mix

A

Dry heparin

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11
Q

Form of heparin that is fast mixing but requires dilution of sample

A

Solution heparin

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12
Q

Form of heparin that…
-decreased electrolytes, HCO3-, Hb
-Increased pO2, Because 02 in heparin solution is equalliberated with atmospheric air

A

Solution heparin

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13
Q

Venous occlusion by tourniquet should be less than _____ Minutes

A

2

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14
Q

Where are the important factors for Specimen collection?

A

-patient should have calm, steady ventilation for 15 minutes, 30 minutes for patients receiving artificial air or CO2
-Pain and anxiety should be minimized
-Sample should be drawn anaerobically in presence of anticoagulants
-Samples with air bubble should be discarded
-Keep Hemolysis to a minimum

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15
Q

How should glass specimens be stored? 

A

-Should be placed on ice/water slurry immediately (Slow down enzymatic activity) 
-stable for about two hours

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16
Q

How should a plastic specimen be stored?

A

-should be analyzed immediately
-Stable for 15 minutes 

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17
Q

Prolonged storage of specimen may decrease _____ and increase ______ (Recommended that samples be analyzed within one hour) 

A

Ca2+, K+

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18
Q

What are the analytical methods for determining acid base balances and blood gas analysis?

A

• pH electrode
•pCO2 electrode
•pO2 electrode

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19
Q

Calibrators, buffers and electrodes must be at the same ________. 

A

Temperature

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20
Q

How is pH electrode calibrated?

A

Calibrated with buffer solutions that bracket pH of sample (Normal 7.35-7.45) 

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21
Q

pCO2 electrode is a __________ pH Electrode.

A

Modified

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22
Q

How does pCO2 electrode determine pH?

A

Takes a vantage that pH has a linear relationship to log pCO2 Over the range of 10-90 mmHg (normal pCO2 is about 35 to 45 mmHg)

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23
Q

What is normal pCO2 range?

A

35-45 mmHg

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24
Q

 what are the two types of pCO2 electrode? 

A

-invasive: Requires blood to be drawn
-Noninvasive: Transcutaneous pCO2 (tcpCO2) 

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25
Q

How is invasive pCO2 electrode calibrated?

A

Zero gas and a slope gas (40 mmHg)
- Usually bubbled through a humidifier to include contribution of water vapor pressure

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26
Q

Non-invasive transcutaneous pCO2, has the same detection principle Except detection occurs on skin (Require scan to be warmed to _______ Degrees Celsius)
-Electrode for CO2 accumulation during analysis
-calibration is to gas mixture‘s (same s other)

A

42-43

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27
Q

What is normal pO2?

A

80-110 mmHg

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28
Q

pO2 Electrode is also known as _____________ electrode.
-Invasive, requires blood to be drawn

A

Clark Polargraph

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29
Q

-Specificity of electrode is dependent on membrane permeability
-O2 is consumed, current is proportional to [O2]

A

pO2 Electrode

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30
Q

How is p02 electrode calibrated?

A

Two gases (Zero and another with O2)

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31
Q

Noninvasive, transcutaneous pO2 (tcpO2) Same detection except occurs on the skin and requires a skin to be __________. 

A

Warmed

-calibration is atmospheric O2

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32
Q

How is sample OD measured?

A

Dilutant O.D. (Your measurement) X stock concentration /

Stock O.D. (Given)

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33
Q

OD and Concentration have a __________ Relationship. 

A

Linear

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34
Q

How is anion gap calculated?

A

(Na + K) - (Cl- HCO3) = 15 mmol/L (10-20)

(Na) + ( Cl - HCO3) = 12 mmol/L (7-16)

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35
Q

What are possible sources of error when measuring electrolytes?

A

-Lipemic blood
-Hemolysis (special attention to potassium)
-Storage temperature
-Timing of plasma separation

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36
Q

Glass membrane electrodes are used for….

A

Sodium*

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37
Q

Valinomycin coated polyvinyl chloride electrodes are used for…

A

Potassium*

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38
Q

What type of spectroscopy is used for detecting sodium and potassium? 

A

Flame atomic emission spectroscopy
Or ion selective electrode is used

39
Q

What is most commonly used for chemistry testing, Serum or plasma?

A

Serum

If plasma is used, do not use EDTA Anticoagulant

40
Q

Is capillary blood is used what temperature does it need to be to cause vasodilation?

A

40 degrees Celsius

41
Q

For electrolyte testing, what temperature is needed for specimen storage?

A

4°C

37°C, oxygen Use is increased (Enzymes) That can result in hypoxic tissues and Can cause cell death/hemolysis 

42
Q

Why is timing of plasma separation important?

A

Living cells release metabolites that alter levels or cause Hemolysis

43
Q

ion selective electrodes:

Is direct or indirect effected by hyperlipidemia?

A

Indirect (Diluted)*

44
Q

How does ion selective electrode work?

A

Two different electrodes, one is exposed to liquid of known pH (Reference electrode)
The other is exposed to the sampleMeasures the change between the two electrodes

45
Q

What method for detecting sodium and potassium is highly sensitive and accurate and used as the reference method?

A

Flame atomic emission spectroscopy 

46
Q

flame atomic emission spectrum Spectroscopy isn’t a popular method for Sodium and potassium measurement but is very important for what? 

A

Measuring calcium and magnesium levels!***

47
Q

Flame atomic emission spectroscopy:

Difference in voltage change is proportional to…..

A

Concentration of the sample

48
Q

What is the disadvantage of flame atomic emission spectroscopy?

A

Protein will interfere with the test
-Pseudohyponatremia and pseudohypochloremia
-Potassium is less effected (Too low to matter)


49
Q

Flame atomic emission spectroscopy: 

Na- ______nm

A

589

50
Q

Flame atomic emission spectroscopy:

K ______nm

A

766 nm

51
Q

Flame atomic emission spectroscopy:

Cs- ______nm

A

852

52
Q

Flame atomic emission spectroscopy:

Li ______nm

A

671

53
Q

Flame atomic emission spectroscopy:

Intensity of emitted light is proportional to…

A

Sample

54
Q

Flame atomic emission spectroscopy is an __________ a method that requires dilution

A

Indirect

55
Q

________ should be used for potassium detection (Potassium is released during clotting or Hemolysis) 

A

Plasma

56
Q

What should not be used for sodium and potassium?

A

Na heparin or
NH4-heparin (Increases hydrogen and pH which can cause Hemolysis, leakage, and increased potassium)

57
Q

How long are sodium and potassium samples good for? 

A

-whole blood must be analyzed within three hours
-Plasma, serum, and urine are stable For one week at room temperature or 4°C
-Stable for one year at -20°C


58
Q

Chloride interferes with other….

A

Halides

59
Q

What are the four methods for detecting chloride?

A

-coulometric titration
-Mercuric Thiocyanate Spectroscopy
-ISE
-Schales and Schales Titration


60
Q

Which method for detecting chloride is the preferred method That is very accurate?

A

coulometric titration

61
Q

Method of detecting chloride that Detects excess silver to signal the endpoint

A

coulometric titration

  • The more chloride there is, the longer till silver is detected
62
Q

What method is good for detecting chloride that is in normal range (80-125 mM)? 

A

Mercuric Thiocyanate Spectroscopy

63
Q

Why can’t Mercuric Thiocyanate Spectroscopy be used for detecting low chloride levels? 

A

There is signal noise at lower chloride levels

64
Q

Method for detecting chloride:

• Ferric-Isothlocyanate
(Colorimeticaly) Color
• Extremely temperature sensitive
Interfering factor: Bilirubin, Hb, &
llpemia

A

Mercuric Thiocyanate Spectroscopy

65
Q

Method for detecting chloride that is the most common method? 

A

ISE

-Direct
-Indirect

66
Q

Method for detecting chloride that uses Ag-AgCl or Ag-S sensing elements 

A

ISE

-has the same limitations as sodium and potassium

67
Q

-Chloride ions in serum or complex with mercury nitrite** to form soluble HgCl2*
-serum proteins are precipitated with tungstic acid
-soluble fraction is titrated with mercuric nitrate in the presence of s-diphenylcarbazone as indicator 

A

Schales and Schales Titration

68
Q

In Schales and Schales Titration, when does the indicator turn violet-blue?

A

With first excess of mercuric ion

-value is calculated by how much Mercuric nitrate is left in the dropper

69
Q

What may secure the endpoint in  Schales and Schales Titration?

A

Bilirubin or hemoglobin

70
Q

What causes the violet color in Schales and Schales Titration? 

A

Hg2 + diphenylcarbazone —-> violet color

71
Q

What kind of sample is used for cystic fibrosis screening in newborns?

A

Sweat chloride**

72
Q

What specimens are used to measure sweat chloride? 

A

Serum, heparinized plasma, urine, sweat, and other body fluids

73
Q

Why should all fluids be rapidly separated from cells When testing for chloride?

A

To avoid pH changes (Associated with bicarbonate and chloride) and shift in ionic equilibrium due to cellular metabolism

74
Q

ISE Measurements of whole blood should be performed within _____ hours 

A

2

75
Q

Choroid and serum, plasma, urine and other fluids are stable for _______ at room temperature, and at both 2 and -20°C

A

1 week

76
Q

What causes cystic fibrosis?
What are three things that it can effect?

A

Defect in CFTR protein*****

-electrical balance
-COPD disease
-Pancreatic instability

77
Q

What is the normal range for sweat chloride?

What is the range for cystic fibrosis?

A

0-40 mmol/L

Less than 60 mmol/L

78
Q

What induces sweating in the sweat chloride test?

A

Pilocarpine**

79
Q

How is the sweat chloride test performed?

A

-Metal electrode is used to drive medicine into the skin (pilocarpine)
-Sample is collected in gauze for measurement
***

80
Q

What are the percentages of the three different carbon sources? need to know

A

CO2- 3%
Carbamino derivatives of plasma proteins- 33%
HCO3- 64% 

81
Q

What is the normal values for bicarbonate?

A

22-30 mmol/L (method dependent) ***

82
Q

 what are the three lab methods for detecting HCO3 (total CO2)? 

A

-Manometric (gas pressure)
-Spectrophotometric (color change)
-pCO2 electrode (Measures pressure gradient) Monitored by glass pH electrode

  • Are they all acidify the sample to convert all CO2 forms to CO2 gas
83
Q

What is the most common method to measure all CO2 forms? 

A

Enzymatic- Spectrophotometric***

84
Q

Enzymatic- Spectrophotometric:

All CO2 forms are converted to bicarbonate by addition of __________.
NADH consumption measured as decrease in _______ nm absorption. 

A

Alkali serum*
340 (NEED TO KNOW THIS!!!)*

85
Q

 Enzymatic- Spectrophotometric measures production of ________ or  consumption of _________.

A

NDH, NADH

86
Q

What kind of specimen is used for total CO2 measurement?

A

Serum, HEPARINIZED plasma,
• CANNOT use other anticoagulant (disturb erythrocyte and plasma CO)
Whole blood cannot be used due to heme-bound CO and carbamino-
bound CO2

87
Q

What is the major source of error associated with total CO2 measurements?

A

Handling of sample
-Exposure to air should be minimal and centrifugation at 37°C tightly stop right before analysis

88
Q

How long is serum or plasma total CO2 stable for?

A

For several days at 4°C

89
Q

Color change from orange to yellow

A

540 nm

90
Q

Color change from yellow to green

A

560 nm

91
Q

Color change from green to blue

A

490

92
Q

Color change from blue to violet

A

430

93
Q

Color change from violet to red

A

400-700??

94
Q

Color change from red to orange

A

630

Clinical Chemistry Lab (7 decks)

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