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Mercy CLS 5: Chemistry > 10) Blood gases and pH > Flashcards

10) Blood gases and pH Flashcards

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1
Q

2 components of bicarb buffer system

A

Dissolved carbon dioxide gas (CO2)
Bicarbonate ion (HCO3-)

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2
Q

1 atm = —- mmHg

A

760

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3
Q

gas solubility constant

A

How much gas dissolves for each 1 mmHg of partial pressure of that gas.

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4
Q

CO2 solubility constant

A

0.03 mmol/L per mmHg

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5
Q

concentration of CO2

A

[CO2] = (pCO2)(0.03)

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6
Q

Lung disease can ——- the pressure and hyperventilation can ——- the pressure

A

increase
decrease

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7
Q

CO2 + H2O →

A

H2CO3
carbonic acid

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8
Q

H2CO3 →

A

H + HCO3

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9
Q

enzyme catalyzing change from CO2 to bicarb

A

carbonic anhydrase

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10
Q

—% of CO2 is present as bicarbonate.
—% is bound to hemoglobin as a carbamino compound.
—% is present as dissolved gas.

A

75
20
5

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11
Q

buffer

A

a solution containing a weak acid and its conjugate base that resists changes in pH when a strong acid or base is added

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12
Q

4 blood buffers

A

Bicarbonate
Hemoglobin
Phosphorus
Proteins

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13
Q

Henderson-Hasselbalch Equation

A

pH = pKa + log[cHCO3/(𝛼)(pCO2)]

pKa = 6.1
𝛼 = 0.03

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14
Q

bicarb RR

A

22-26 mmol/L

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15
Q

pCO2 RR

A

35-45 mmHg

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16
Q

normal bicarbonate:carbonic acid ratio

A

20:1

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17
Q

Hemoglobin accounts for about —-% of buffering capacity, but is the 2nd most important buffering system.

A

80

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18
Q

hemoglobin functions

A

Transports H+, O2 and CO2

Allows for large amounts of CO2 to be carried in the blood with little or no change in pH.

Participates in the chloride shift to maintain neutral charge within the RBC

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19
Q

Accounts for only about 1% of blood buffering capacity

A

phosphate buffer system

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20
Q

Account for about 14% of blood buffering capacity.

A

proteins

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21
Q

Proteins are primarily —— buffers.

A

cellular

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22
Q

diffusion

A

movement of an uncharged, hydrophobic solute through a lipid bilayer.

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23
Q

external convection system

A

lungs, the airway, and respiration muscles

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24
Q

internal convection system

A

circulatory system

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25
Q

Refers to a set of anatomical features involved with respiration and includes the larynx, trachea, bronchi, lungs, and pleura.

A

respiratory apparatus

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26
Q

6 functions of the respiratory apparatus

A
  1. Provide a means of moving outside air to the alveolar air spaces.
  2. Provide a means to carry O2 and CO2 in the blood.
  3. Provide a surface for gas exchange.
  4. Contain an internal convection system and a circulatory system that consists of a four-chamber heart.
  5. Provide a mechanism for locally regulating ventilation and perfusion.
  6. Provide a mechanism for centrally regulating ventilation.
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27
Q

Hemoglobin can bind O2 only when the iron is in the…

A

ferrous (Fe2+) state

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28
Q

Most important amino acid in heme is ——-, which binds Fe2+.

A

histidine

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29
Q

Shows the relationship between percent hemoglobin saturation with oxygen

A

The Hemoglobin-Oxygen Dissociation Curve

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30
Q

reasons for S-shaped Hb-O2 curve

A

involve the four oxygen binding sites on the hemoglobin molecule.

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31
Q

factors that can cause Hb-O2 curve to shift left (higher affinity)

lung environment

A
  • ↑ pH
  • ↓ pCO2
  • ↓ 2,3-DPG
  • ↓ temp
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32
Q

factors that can cause Hb-O2 curve to shift right (lower affinity)

muscle environment

A
  • ↓ pH
  • ↑ pCO2
  • ↑ 2,3-DPG
  • ↑ temp
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33
Q

hemoglobin is intrinsically sensitive to…

A

High temperatures
High pCO2
Low p H

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34
Q

5 different forms CO2 is transported in

A

Bicarbonate (primarily)
Carbonate
Carbonic acid
Dissolved carbon dioxide
Carbamino compounds

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35
Q

Cl-HCO3 exchanges

A

chloride/hamburger shift

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36
Q

difference between serum and urine pH represents…

A

kidneys’ attempt to excrete nonvolatile acids that are produced by metabolic processes.

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37
Q

3 mechanisms that facilitate renal excretion of acid, and retention of bicarb

A
  • Na-H exchange
  • production of ammonia, excretion of ammonium
  • reclamation of bicarb
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38
Q

chloride shift in venous blood

A

HCO3 out of rbcs
Cl into rbcs

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39
Q

chloride shift in arterial blood

A

HCO3 into rbcs
Cl out of rbcs

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40
Q

An acid-base disorder is primary if…

A

the imbalance results from a change in pCO2 or HCO3- (one disturbance only)

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41
Q

Result of more than one pathologic process occurring in an individual

A

mixed acid-base disorders

42
Q

pO2 RR

A

85-108 mmHg

43
Q

tCO2 RR

A

22-28 mEq/L

44
Q
A

Siggaard-Andersen Acid-Base Chart

45
Q

metabolic acidosis general causes

A
  • Impaired renal excretion of fixed acids
  • Overproduction or administration of fixed acids
  • Primary bicarbonate loss via kidneys or gastrointestinal tract (base out the bottom)
  • Secondary bicarbonate loss attributable to elevated serum chloride levels
46
Q

metabolic acidosis + normal AG

A
  • Renal tubular acidosis
  • Increased serum chloride, which results in suppressed bicarbonate ion resorption
  • Diarrhea
  • DKA recovery
  • TPN
  • Carbonic anhydrase inhibitors
  • Ureterosigmoidostomy
47
Q

metabolic acidosis + high AG

A
  • Renal failure
  • Diabetic ketoacidosis
  • Lactic acidosis
  • Acetylsalicylic acid, methanol, formic acid, isopropyl alcohol, and ethylene glycol (MUDPILES)
48
Q

metabolic alkalosis general causes

A

Addition of base to the body
Decrease in the amount of base leaving the body
Loss of acid-rich fluids

49
Q

——– causes are categorized by Cl responsiveness or resistance

A

metabolic alkalosis

50
Q

causes of metabolic alkalosis

A

Via gastrointestinal tract
Vomiting and nasogastric suction
Chloride-losing diarrhea states
Renal failure
Hypercalcemia (milk-alkali syndrome)
Hormonal (hypoaldosteronism, adrenal hyperplasia, Cushing’s, pituitary adenomas)
Hypokalemia
Retention of bicarbonate ion
Administration of alkali (antacids)
Overuse of diuretics

51
Q

respiratory acidosis causes

A

Diffusion
Alveolar destruction (emphysema)
Cancer (thickened alveolar membrane)
Congestive heart failure (fluid buildup)

CNS
Impaired respiratory drive
Trauma
Tumor
Vascular disorders
Epilepsy
Hypoxia
Drug ingestion (barbiturates, narcotics)
Degenerative disorders
Sleep apnea

Impaired respiratory mechanics
Polio
Respiratory muscle (dystrophy)
Trauma to the ribs

Airway obstruction
Tumors
Food/vomitus
COPD and asthma

52
Q

causes of weakened respiratory muscle function

A

Myasthenia gravis
Periodic paralysis
Intraperitoneal aminoglycosides
Guillain–Barré syndrome
Botulism
Poliomyelitis
Amyotrophic lateral sclerosis (A L S)
Myxedema

53
Q

chloride-responsive metabolic alkalosis

A
  • diuretics
  • vomiting
  • NG tube suction
  • villous adenoma
  • carbenicillin
  • contraction alkalosis
54
Q

chloride-resistance metabolic alkalosis

A
  • hyperaldosteronism
  • cushings
  • exogenous steroids
  • licorice (glycyrrhizin)
  • bartter syndrome
  • milk-alkali syndrome
55
Q

respiratory alkalosis causes

A

Hypoxemia
Pneumonia, emboli
Congestive heart failure
High-altitude exposure
Severe anemia

Stimulation of the Medullary Respiratory Center
Hyperventilation syndrome (anxiety)
Hepatic encephalopathy
Salicylate intoxication
Pregnancy (increased progesterone)
Neurologic disorders (CVA)
GN sepsis

Excessive mechanical ventilation
Recovery from metabolic acidosis

56
Q

3 general methods of compensation

A

buffers
renal
respiratory

57
Q

One acid/base component is abnormal, while one is normal

A

uncompensated

58
Q

The second component is now starting to offset the other by going in the same direction to help pH

A

partial compensation

59
Q

The pH is now normal, because the acid/base components have responded

A

fully compensated

60
Q

compensation for met. alk.

A

Lungs hypoventilate to hold CO2. Kidneys reclaim less HCO3.

61
Q

compensation for met. acid.

A

Lungs hyperventilate to lose CO2. Kidneys reclaim more HCO3.

62
Q

compensation for resp. alk

A

Kidneys reclaim less HCO3.
Lungs hypoventilate to hold CO2.

63
Q

compensation for resp. acid.

A

Kidneys reclaim more HCO3.
Lungs hyperventilate to lose CO2.

64
Q

venous tCO2 RR

A

22-29 mmol/L

65
Q

recommended site for ABG draw

A

radial artery

66
Q

pH and blood gas sample

A

whole blood

67
Q

anticoag for pH & blood gas

A

balanced heparin

68
Q

sources of ABG error

A

Metabolism (glycolysis continues)
Diffusion of gases through the plastic container
Elevated potassium values (hemolysis)

69
Q

preanalytical handling of ABG samples

A

Every effort must be made to remove air bubbles immediately and without agitation.

Sample should be mixed immediately to dissolve the heparin and prevent clotting.

Samples should be mixed thoroughly before injection into the blood-gas analyzer.

70
Q

sample requirements for ABG

A
  • Arterial or venous specimen tightly stoppered
  • Heparinized syringe
  • On ice (slow metabolism) — good for 2 hours, or 30 mins not on ice
  • No air bubbles
  • Perform ASAP
71
Q

indirect pH/ABG measures

A

HCO3-
H-H equation

72
Q

——- of RBCs used in order to spill and measure hemoglobin

A

Ultrasonic lysis

73
Q

Measurement of potential (voltage) between two electrodes in a solution.

A

potentiometry

74
Q

explain reference and indicator electrode

A

Reference electrode: Electrode with a constant voltage
Indicator electrode (Na, K, Cl): The measuring electrode

75
Q

Measured cell potential is related to the molar concentration by the —— equation

A

nernst

76
Q

4 important attributes of a reference electrode

A
  1. Potential is reversible and obeys the Nernst equation
  2. Electrode exhibits a potential that is constant with time
  3. Electrode returns to its original potential after being subjected to small currents
  4. Electrode exhibits little hysteresis or lag with temperature cycling
77
Q

ion selective electrode

A

membrane-based electrochemical transducer capable of responding to a specific ion

78
Q

ISE advantages over other methods

A

Fast, sensitive, direct measurement, no reagents needed, selective, easy to maintain, precise, and cost-effective (can be reused)

79
Q

pH electrode membrane

A

layers of hydrated and unhydrated glass

80
Q

usually silver/silver chloride serves as a reference electrode

A

pH

81
Q

pCO2 electrode membrane

A

gas-permeable membrane (Teflon or silicone)

82
Q

measuring the quantity of electricity needed to convert the analyte quantitatively to a different oxidation states

A

coulometry

83
Q

the quantity of electricity or charge that is transported in one second by a constant current of one ampere

A

coulomb

84
Q

Measurement of the current flow produced by an oxidation-reduction reaction

A

amperometry

85
Q

sweat chloride methodologies

A

Coulometry
Amperometry

86
Q

gas-permeable membrane, usually polypropylene, that allows dissolved oxygen to pass through, but nothing else

A

Clark pO2 gas-sensing electrode

87
Q

information about the analyte is derived from the measurement of current as a function of an applied potential obtained under conditions that promote polarization of an indicator, or working, electrode

A

voltammetry

88
Q

Measurement of lead in whole blood samples methodology

A

Anodic stripping voltammetry

89
Q

a measure of the ability of a solution to carry an electric current.

A

conductometry

90
Q

The electrical resistance in ohms measured between opposite faces of a 1.00-centimeter cube of an aqueous solution at a specific temperature.

A

resistivity

91
Q

pH values of calibration materials

A

6.8
7.4

92
Q

frequency of gas calibration

A

One-point calibrations done every 30 min and 4 hrs

93
Q

why is calibration important?

A

the calibration curve, or data, is used to generate all other results for quality control and patient samples

94
Q

frequency of pH/ABG QC

A

all three levels of controls assayed within a 24h period (one each 8hr interval)

95
Q

most ABG errors occur in the —– stage

A

preanalytical

96
Q

temperature correction is useful for…

A

patients who have been exposed to low temps for a prolonged period

97
Q

room air contamination effects on results

A

↑ pH
↓ pCO2
↑ pO2

98
Q

old sample effects on results

A

↓ pH
↑ pCO2
↓ pO2

99
Q

the mEq/L base needed to change whole blood pH by 0.01 unit

A

Hemoglobin-dependent base excess

100
Q
A

Siggaard-Andersen Alignment Nomogram

Mercy CLS 5: Chemistry (24 decks)

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