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Biochemistry > Chapter 16 - Acid/Base Balance > Flashcards

Chapter 16 - Acid/Base Balance Flashcards

1
Q

pO2 reference interval (arterial blood)

A

80-100 mm Hg

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1
Q

pH reference interval (arterial blood)

A

7.35-7.45

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2
Q

pCO2 reference interval (arterial blood)

A

35-45 mm Hg

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3
Q

HCO3 Reference interval (arterial blood)

A

22-26 mEq/L

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4
Q

Base Excess reference interval (arterial blood)

A

-2 to 2 mEq/L

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5
Q

What are the measurements that are directly measured by an electrode in arterial blood?

A

pH
pO2
pCO2

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6
Q

What are the measurements that are calculated in arterial blood?

A

HCO3
Base Excess

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7
Q

What does a negative base excess imply?

A

Acidosis

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8
Q

What does a positive base excess imply?

A

Alkalosis

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9
Q

What is base excess?

A

The amount of excess or insufficient bicarbonate?

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10
Q

Pulse oximetry reference interval

A

95-100%

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11
Q

What does pulse oximetry measure?

A

Oxygen saturation of hemoglobin

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12
Q

Boyle’s Law

A

At a constant temperature, the volume of a gas varies inversely to the pressure exerted to contain it

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13
Q

Charles’s Law

A

At a constant pressure, the volume of a gas varies with temperature (increases as it increases)

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14
Q

Dalton’s Law

A

Total pressure of gas mixture is the sum of the partial pressures of each gas

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15
Q

Henry’s Law

A

The amount of a dissolved gas is proportional to the partial pressure of the gas over the liquid

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16
Q

Specimens have to be contained (capped) or gas will escape. Which Law does this correspond to and why?

A

Boyle’s Law
At a constant temp, inc Vol. = dec Pressure

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17
Q

Blood gas assays are temperature dependent. Which Law does this correspond to and why?

A

Charles’s Law
At a constant pressure, inc temp = inc volume

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18
Q

Blood has more than one gas in it, and we can measure pressures individually. Which Law does this correspond to and why?

A

Dalton’s Law
Total Pressure = Sum of partial pressures

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19
Q

Gas that diffuses from the blood sample is proportional to the blood concentration. Which Law does this correspond to and why?

A

Henry’s Law
Dissolved gas = partial pressure of gas above liquid

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20
Q

Where are gasses in the blood that we use to measure partial pressures?

A

Dissolved in plasma
and
Combined with hemoglobin

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21
Q

Describe the process of gas transfer of O2 and CO2 at the tissue

A

O2 RBC –> O2 Tissues
CO2 Tissues –> CO2 RBC
CO2 + H2O (Carbonic Anhydrase) —> H2CO3 (Carbonic Acid)
Carbonic Acid —> HCO3 + H+
Chloride Shift
Hemoglobin buffers Hydrogen ion

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22
Q

Describe the process of gas transfer of O2 and CO2 at the lung

A

O2 Lung –> O2 RBC
Reverse Chloride Shift
Hemoglobin releases H+
HCO3 + H+
Carbonic Acid/H2CO3 (Carbonic Anhydrase) –> CO2 + H2O
CO2 RBC –> CO2 Lung

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23
Q

At pO2 of 30, what percent of hemoglobin is saturated?

A

50%

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24
Q

At pO2 of 50, what percent of hemoglobin is saturated?

A

80%

25
Q

At pO2 of 60, what percent of hemoglobin is saturated?

A

90%

26
Q

At pO2 of 80, what percent of hemoglobin is saturated?

A

100%

27
Q

Hemoglobin behavior is influenced by what factors

A

pH
pCO2
Temperature
2,3 DPG levels

28
Q

What happens to hemoglobin saturation at pO2 of 30, if in left shift?

A

Instead of 50% Hgb saturation, it’s increased at 70%.

29
Q

How should you mix an ABG tube?

A

Roll on 3 axes for 2 minutes
Undermining = clots

29
Q

Collection protocol for measurement of arterial blood gases

A

Dry heparin
Short bevel
No tournique
No air/bubbles

30
Q

What makes effects of air/bubbles worse

A

Big difference between ambient air and patient pO2
Lower temperature
Agitated sample
Bubbles big or exposed to blood too long

31
Q

Glass syringes for ABG should be analyzed when

A

No more than 1 hour on ice

32
Q

Plastic syringes for ABG should be analyzed when

A

Within 30 minutes at room temperature

33
Q

Why should plastic syringes not be put on ice

A

Cold makes the syringes more permeable to oxygen and increases hemolysis

34
Q

PO2 electrode

A

Oxygen passes through gas permeable membrane
Reacts with polarized platinum electrode
Reduced and generates a current
Current = oxygen concentration

35
Q

pCO2 electrode

A

CO2 passes gas permeable membrane
Enters sodium bicarbonate buffer soon
Reacts with buffer producing carbonic acid, changing pH
pH change sensed by internal pH electrode
pH decreases in proportion to CO2 present

36
Q

pH electrode

A

H+ migrates into outer layer of glass, replacing sodium ions
Chrloide ions are drawn into the inner membrane surface
Silver ions are released by the internal silver/silver chloride element
Voltage changes in proportion to the H+ concentration

37
Q

Henderson-Hasselback equation

A

Formula to determine bicarb
pH = 6.1 + log ( HCO3/ 0.0306 * pCO2)

38
Q

Alternate ABG specimens

A

Venous
Arterialized capillary blood

39
Q

How are arterialized capillary blood samples prepared

A

Finger warmed for 10 minutes
Systolic bp must be at least 95 mm Hg

40
Q

How does a delay in analysis affect ABG specimens

A

Oxygen consumed
Acidic pH, Glycolysis produces CO2

41
Q

Effects of metabolism worse when what cells are high?

A

Retics
Platelets
WBC

42
Q

Species with high WBC and PLT need to be analyzed within how long?

A

5 minutes

43
Q

When should specimen be analyzed at RT? Why?

A

Within 30 minutes
Bcz metabolism at RT causes non significant effect within first hour

44
Q

How do bubbles in specimen affect ABG samples

A

pO2 false increase
pCO2 false decrease
pO2 false decrease if PT on oxygen therapy (PO2 > 150)

45
Q

How do poorly sealed specimens affect ABG levels

A

Gases escape causing lower pO2 and pCO2
pH false increase

46
Q

What temp are ABG specimens tested at?

A

37C

47
Q

Pulse oximetry method

A

Red and Infrared lights shine into photo detector, difference between pulses = oxygenated vs deoxygenated blood

48
Q

How much more tightly does CO bind hemoglobin than O2?

A

250 times more likely

49
Q

Can carboxyhemoglobin bind oxygen?

A

NO

50
Q

S/S of carbon monoxide poisoning

A

headache
dizziness
weakness
nausea
vomiting
chest pain
altered mental status
death

51
Q

Diagnostic measurement of carboxyhemoglobin in nonsmokers vs smokers?

A

2% carboxyhemoglobin non
9% carboxyhemoglobin smokers

52
Q

CO treatment?

A

100% oxygen inhalation for 4-5 hours

53
Q

Reference Method for CO measurement

A

Gas chromatography

54
Q

Gas chromatography advantages

A

More sensitive than spectrophotometry
More expensive, but not as fast

55
Q

Best method for measuring CO levels >2-3%

A

Spectrophotometry

56
Q

A pH of 6 is how much more acidic than 7?

A

10x

57
Q

A pH of 5 is how much more acidic than 7?

A

100x

58
Q

Each unit of pH change represents how much of a change in acidity or alkalinity?

A

10 fold

59
Q

Calculated pH

A

-log (H+)

60
Q
A

Biochemistry (26 decks)

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