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Clinical Chemistry-Blood Gases, pH, and Electrolytes Flashcards

(70 cards)

1
Q
  1. Which of the following represents the
    Henderson–Hasselbalch equation as applied
    to blood pH?
    A. pH = 6.1 + log HCO3–/PCO2
    B. pH = 6.1 + log HCO3–/(0.03 × PCO2)
    C. pH = 6.1 + log dCO2/HCO3–
    D. pH = 6.1 + log (0.03 × PCO2)/HCO3–
A

B. pH = 6.1 + log HCO3–/(0.03 × PCO2)

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2
Q
  1. What is the PO2 of calibration gas containing
    20.0% O2, when the barometric pressure is
    30 in.?
    A. 60 mm Hg
    B. 86 mm Hg
    C. 143 mm Hg
    D. 152 mm Hg
A

C. 143 mm Hg

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3
Q
  1. What is the blood pH when the partial pressure
    of carbon dioxide (PCO2) is 60 mm Hg and the
    bicarbonate concentration is 18 mmol/L?
    A. 6.89
    B. 7.00
    C. 7.10
    D. 7.30
A

C. 7.10

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4
Q
  1. Which of the following best represents the
    reference (normal) range for arterial pH?
    A. 7.35–7.45
    B. 7.42–7.52
    C. 7.38–7.68
    D. 6.85–7.56
A

A. 7.35–7.45

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5
Q
  1. What is the normal ratio of bicarbonate to
    dissolved carbon dioxide (HCO3

    :dCO2) in
    arterial blood?
    A. 1:10
    B. 10:1
    C. 20:1
    D. 30:1
A

C. 20:1

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6
Q
  1. What is the PCO2 if the dCO2 is 1.8 mmol/L?
    A. 24 mm Hg
    B. 35 mm Hg
    C. 60 mm Hg
    D. 72 mm Hg
A

C. 60 mm Hg

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7
Q
  1. In the Henderson–Hasselbalch expression
    pH = 6.1 + log HCO3

    /dCO2, the
    6.1 represents:
    A. The combined hydration and dissociation
    constants for CO2 in blood at 37°C
    B. The solubility constant for CO2 gas
    C. The dissociation constant of H2O
    D. The ionization constant of sodium bicarbonate
    (NaHCO3)
A

A. The combined hydration and dissociation
constants for CO2 in blood at 37°C

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8
Q
  1. Which of the following contributes the most to
    the serum total CO2?
    A. PCO2
    B. dCO2
    C. HCO3–
    D. Carbonium ion
A

C. HCO3–

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9
Q
  1. In addition to sodium bicarbonate, what other
    substance contributes most to the amount of base
    in the blood?
    A. Hemoglobin concentration
    B. Dissolved O2 concentration
    C. Inorganic phosphorus
    D. Organic phosphate
A

A. Hemoglobin concentration

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10
Q
  1. Which of the following effects results from
    exposure of a normal arterial blood sample to
    room air?
    A. PO2 increased PCO2 decreased pH increased
    B. PO2 decreased PCO2 increased pH decreased
    C. PO2 increased PCO2 decreased pH decreased
    D. PO2 decreased PCO2 decreased pH decreased
A

A. PO2 increased PCO2 decreased pH increased

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11
Q
  1. Which of the following formulas for O2 content is
    correct?
    A. O2 content = %O2 saturation/100 × Hgb g/dL ×
    1.39 mL/g + (0.0031 × PO2)
    B. O2 content = PO2 × 0.0306 mmol/L/mm
    C. O2 content = O2 saturation × Hgb g/dL
    × 0.003 mL/g
    D. O2 content = O2 capacity × 0.003 mL/g
A

A. O2 content = %O2 saturation/100 × Hgb g/dL ×
1.39 mL/g + (0.0031 × PO2)

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12
Q
  1. The normal difference between alveolar and
    arterial PO2 (PAO2–PaO2 difference) is:
    A. 3 mm Hg
    B. 10 mm Hg
    C. 40 mm Hg
    D. 50 mm Hg
A

B. 10 mm Hg

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13
Q
  1. A decreased PAO2–PaO2 difference is found in:
    A. A/V (arteriovenous) shunting
    B. V/Q (ventilation/perfusion) inequality
    C. Ventilation defects
    D. All of these options
A

C. Ventilation defects

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14
Q
  1. The determination of the oxygen saturation of
    hemoglobin is best accomplished by:
    A. Polychromatic absorbance measurements of a
    whole-blood hemolysate
    B. Near infrared transcutaneous absorbance
    measurement
    C. Treatment of whole blood with alkaline
    dithionite prior to measuring absorbance
    D. Calculation using PO2 and total hemoglobin
    by direct spectrophotometry
A

A. Polychromatic absorbance measurements of a
whole-blood hemolysate

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15
Q
  1. Correction of pH for a patient with a body
    temperature of 38°C would require:
    A. Subtraction of 0.015
    B. Subtraction of 0.01%
    C. Addition of 0.020
    D. Subtraction of 0.020
A

A. Subtraction of 0.015

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16
Q
  1. Select the anticoagulant of choice for blood gas
    studies.
    A. Sodium citrate 3.2%
    B. Lithium heparin 100 U/mL blood
    C. Sodium citrate 3.8%
    D. Ammonium oxalate 5.0%
A

B. Lithium heparin 100 U/mL blood

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17
Q
  1. What is the maximum recommended storage time
    and temperature for an arterial blood gas sample
    drawn in a plastic syringe?
A

D.

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18
Q
  1. A patient’s blood gas results are as follows:
    pH = 7.26
    dCO2 = 2.0 mmol/L
    HCO3– = 29 mmol/L

These results would be classified as:
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis

A

C. Respiratory acidosis

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19
Q
  1. A patient’s blood gas results are:
    pH = 7.50
    PCO2 = 55 mm Hg
    HCO3– = 40 mmol/L

These results indicate:
A. Respiratory acidosis
B. Metabolic alkalosis
C. Respiratory alkalosis
D. Metabolic acidosis

A

B. Metabolic alkalosis

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20
Q
  1. Which set of results is consistent with
    uncompensated respiratory alkalosis?
    A. pH 7.70 HCO3 30 mmol/L PCO2 25 mm Hg
    B. pH 7.66 HCO3 22 mmol/L PCO2 20 mm Hg
    C. pH 7.46 HCO3 38 mmol/L PCO2 55 mm Hg
    D. pH 7.36 HCO3 22 mmol/L PCO2 38 mm Hg
A

B. pH 7.66 HCO3 22 mmol/L PCO2 20 mm Hg

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21
Q
  1. Which of the following will shift the O2 dissociation
    curve to the left?
    A. Anemia
    B. Hyperthermia
    C. Hypercapnia
    D. Alkalosis
A

D. Alkalosis

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22
Q
  1. In which circumstance will the reporting of
    calculated oxygen saturation of hemoglobin
    based on PO2, PCO2, pH, temperature, and
    hemoglobin be in error?
    A. Carbon monoxide poisoning
    B. Diabetic ketoacidosis
    C. Patient receiving oxygen therapy
    D. Assisted ventilation for respiratory failure
A

A. Carbon monoxide poisoning

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23
Q
  1. Which would be consistent with partially
    compensated respiratory acidosis?
    A. pH PCO2 Bicarbonate
    increased increased increased
    B. pH PCO2 Bicarbonate
    increased decreased decreased
    C. pH PCO2 Bicarbonate
    decreased decreased decreased
    D. pH PCO2 Bicarbonate
    decreased increased increased
A

D. pH PCO2 Bicarbonate
decreased increased increased

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24
Q
  1. Which condition results in metabolic acidosis with
    severe hypokalemia and chronic alkaline urine?
    A. Diabetic ketoacidosis
    B. Phenformin-induced acidosis
    C. Renal tubular acidosis
    D. Acidosis caused by starvation
A

C. Renal tubular acidosis

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25
25. Which of the following mechanisms is responsible for metabolic acidosis? A. Bicarbonate deficiency B. Excessive retention of dissolved CO2 C. Accumulation of volatile acids D. Hyperaldosteronism
A. Bicarbonate deficiency
26
26. Which of the following disorders is associated with lactate acidosis? A. Diarrhea B. Renal tubular acidosis C. Hypoaldosteronism D. Alcoholism
D. Alcoholism
27
27. Which of the following is the primary mechanism of compensation for metabolic acidosis? A. Hyperventilation B. Release of epinephrine C. Aldosterone release D. Bicarbonate excretion
A. Hyperventilation
28
28. The following conditions are all causes of alkalosis. Which condition is associated with respiratory (rather than metabolic) alkalosis? A. Anxiety B. Hypovolemia C. Hyperaldosteronism D. Hypoparathyroidism
A. Anxiety
29
29. Which of the following conditions is associated with both metabolic and respiratory alkalosis? A. Hyperchloremia B. Hypernatremia C. Hyperphosphatemia D. Hypokalemia
D. Hypokalemia
30
30. In uncompensated metabolic acidosis, which of the following will be normal? A. Plasma bicarbonate B. PCO2 C. p50 D. Total CO2
B. PCO2
31
31. Which of the following conditions is classified as normochloremic acidosis? A. Diabetic ketoacidosis B. Chronic pulmonary obstruction C. Uremic acidosis D. Diarrhea
A. Diabetic ketoacidosis
32
32. Which PCO2 value would be seen in maximally compensated metabolic acidosis? A. 15 mm Hg B. 30 mm Hg C. 40 mm Hg D. 60 mm Hg
A. 15 mm Hg
33
33. A patient has the following arterial blood gas results: pH = 7.56 PCO2 = 25 mm Hg PO2 = 100 mm Hg HCO3– = 22 mmol/L These results are most likely the result of which condition? A. Improper specimen collection B. Prolonged storage C. Hyperventilation D. Hypokalemia
C. Hyperventilation
34
34. Why are three levels used for quality control of pH and blood gases? A. Systematic errors can be detected earlier than with two controls B. Analytical accuracy needs to be greater than for other analytes C. High, normal, and low ranges must always be evaluated D. A different level is needed for pH, PCO2, and PO2
A. Systematic errors can be detected earlier than with two controls
35
35. A single-point calibration is performed between each blood gas sample in order to: A. Correct the electrode slope B. Correct electrode and instrument drift C. Compensate for temperature variance D. Prevent contamination by the previous sample
B. Correct electrode and instrument drift
36
36. In which condition would hypochloremia be expected? A. Respiratory alkalosis B. Metabolic acidosis C. Metabolic alkalosis D. All of these options
C. Metabolic alkalosis
37
37. Given the following serum electrolyte data, determine the anion gap. Na = 132 mmol/L Cl = 90 mmol/L HCO3– = 22 mmol/L A. 12 mmol/L B. 20 mmol/L C. 64 mmol/L D. Cannot be determined from the information provided
B. 20 mmol/L
38
38. Which of the following conditions will cause an increased anion gap? A. Diarrhea B. Hypoaldosteronism C. Hyperkalemia D. Renal failure
D. Renal failure
39
39. Alcoholism, liver failure, and hypoxia induce acidosis by causing: A. Depletion of cellular NAD+ B. Increased excretion of bicarbonate C. Increased retention of PCO2 D. Loss of carbonic anhydrase
A. Depletion of cellular NAD+
40
40. Which of the following is the primary mechanism causing respiratory alkalosis? A. Hyperventilation B. Deficient alveolar diffusion C. Deficient pulmonary perfusion D. Parasympathetic inhibition
A. Hyperventilation
41
41. Which condition can result in acidosis? A. Cystic fibrosis B. Vomiting C. Hyperaldosteronism D. Excessive O2 therapy
D. Excessive O2 therapy
42
42. Which of the following conditions is associated with an increase in ionized calcium (Cai) in the blood? A. Alkalosis B. Hypoparathyroidism C. Hyperalbuminemia D. Malignancy
D. Malignancy
43
43. Which of the following laboratory results is consistent with primary hypoparathyroidism? A. Low calcium; high inorganic phosphorus Pi B. Low calcium; low Pi C. High calcium; high Pi D. High calcium; low Pi
A. Low calcium; high inorganic phosphorus Pi
44
44. Which of the following conditions is associated with hypophosphatemia? A. Rickets B. Multiple myeloma C. Renal failure D. Hypervitaminosis D
A. Rickets
45
45. Which of the following tests is consistently abnormal in osteoporosis? A. High urinary calcium B. High serum Pi C. Low serum calcium D. High urine or serum N-telopeptide of type 1 collagen
D. High urine or serum N-telopeptide of type 1 collagen
46
46. Which of the following is a marker for bone formation? A. Osteocalcin B. Tartrate resistant acid phosphatase (TRAP) C. Urinary pyridinoline and deoxypyridinoline D. Urinary C-telopeptide and N-telopeptide crosslinks (CTx and NTx)
A. Osteocalcin
47
47. What role do CTx and NTx play in the management of osteoporosis? A. Increased urinary excretion is diagnostic of early stage disease B. Increased levels indicate a low risk of developing osteoporosis C. Decreased urinary excretion indicates a positive response to treatment D. The rate of urinary excretion correlates with the stage of the disease
C. Decreased urinary excretion indicates a positive response to treatment
48
48. What role does vitamin D measurement play in the management of osteoporosis? A. Vitamin D deficiency must be demonstrated to establish the diagnosis B. Vitamin D is consistently elevated in osteoporosis C. A normal vitamin D level rules out osteoporosis D. Vitamin D deficiency is a risk factor for developing osteoporosis
D. Vitamin D deficiency is a risk factor for developing osteoporosis
49
49. Which statement best describes testing recommendations for vitamin D? A. Vitamin D testing should be reserved only for those persons who demonstrate hypercalcemia of an undetermined cause B. Vitamin D testing should be specific for the 1,25(OH)D3 form C. Testing should be for total vitamin D when screening for deficiency D. Vitamin D testing should not be performed if the patient is receiving a vitamin D supplement
C. Testing should be for total vitamin D when screening for deficiency
50
50. The serum level of which of the following laboratory tests is decreased in both VDDR and VDRR? A. Vitamin D B. Calcium C. Pi D. Parathyroid hormone
C. Pi
51
51. Which of the following is the most accurate measurement of Pi in serum? A. Rate of unreduced phosphomolybdate formation at 340 nm B. Measurement of phosphomolybdenum blue at 680 nm C. Use of aminonaptholsulfonic acid to reduce phosphomolybdate D. Formation of a complex with malachite green dye
A. Rate of unreduced phosphomolybdate formation at 340 nm
52
52. What is the percentage of serum calcium that is ionized (Cai)? A. 30% B. 45% C. 60% D. 80%
B. 45%
53
53. Which of the following conditions will cause erroneous Cai results? Assume that the samples are collected and stored anaerobically, kept at 4°C until measurement, and stored for no longer than 1 hour. A. Slight hemolysis during venipuncture B. Assay of whole blood collected in sodium oxalate C. Analysis of serum in a barrier gel tube stored at 4°C until the clot has formed D. Analysis of whole blood collected in sodium heparin, 20 U/mL (low-heparin tube
B. Assay of whole blood collected in sodium oxalate
54
54. Which of the following conditions is associated with a low serum magnesium? A. Addison’s disease B. Hemolytic anemia C. Hyperparathyroidism D. Pancreatitis
D. Pancreatitis
55
55. When measuring calcium with the complexometric dye o-cresolphthalein complexone, magnesium is kept from interfering by: A. Using an alkaline pH B. Adding 8-hydroxyquinoline C. Measuring at 450 nm D. Complexing to EDTA
B. Adding 8-hydroxyquinoline
56
56. Which electrolyte measurement is least affected by hemolysis? A. Potassium B. Calcium C. Pi D. Magnesium
B. Calcium
57
57. Which of the following conditions is associated with hypokalemia? A. Addison’s disease B. Hemolytic anemia C. Digoxin intoxication D. Alkalosis
D. Alkalosis
58
58. Which of the following conditions is most likely to produce an elevated plasma potassium? A. Hypoparathyroidism B. Cushing’s syndrome C. Diarrhea D. Digitalis overdose
D. Digitalis overdose
59
59. Which of the following values is the threshold critical value (alert or action level) for low plasma potassium? A. 1.5 mmol/L B. 2.0 mmol/L C. 2.5 mmol/L D. 3.5 mmol/L
C. 2.5 mmol/L
60
60. Which electrolyte is least likely to be elevated in renal failure? A. Potassium B. Magnesium C. Inorganic phosphorus D. Sodium
D. Sodium
61
61. Which of the following is the primary mechanism for vasopressin (ADH) release? A. Hypovolemia B. Hyperosmolar plasma C. Renin release D. Reduced renal blood flow
B. Hyperosmolar plasma
62
62. Which of the following conditions is associated with hypernatremia? A. Diabetes insipidus B. Hypoaldosteronism C. Burns D. Diarrhea
A. Diabetes insipidus
63
63. Which of the following values is the threshold critical value (alert or action level) for high plasma sodium? A. 150 mmol/L B. 160 mmol/L C. 170 mmol/L D. 180 mmol/L
B. 160 mmol/L
64
64. Which of the following conditions is associated with total body sodium excess? A. Renal failure B. Hyperthyroidism C. Hypoparathyroidism D. Diabetic ketoacidosis
A. Renal failure
65
65. Which of the following conditions is associated with hyponatremia? A. Diuretic therapy B. Cushing’s syndrome C. Diabetes insipidus D. Nephrotic syndrome
A. Diuretic therapy
66
66. Which of the following conditions involving electrolytes is described correctly? A. Pseudohyponatremia occurs only when undiluted samples are measured B. Potassium levels are slightly higher in heparinized plasma than in serum C. Hypoalbuminemia causes low total calcium but does not affect Cai D. Hypercalcemia may be induced by low serum magnesium
C. Hypoalbuminemia causes low total calcium but does not affect Cai
67
67. Which of the following laboratory results is usually associated with cystic fibrosis? A. Sweat chloride greater than 60 mmol/L B. Elevated serum sodium and chloride C. Elevated fecal trypsin activity D. Low glucose
A. Sweat chloride greater than 60 mmol/L
68
68. When performing a sweat chloride collection, which of the following steps will result in analytical error? A. Using unweighed gauze soaked in pilocarpine nitrate on the inner surface of the forearm to stimulate sweating B. Collecting more than 75 mg of sweat in 30 minutes C. Leaving the preweighed gauze on the inside of the arm exposed to air during collection D. Rinsing the collected sweat from the gauze pad using chloride titrating solution
C. Leaving the preweighed gauze on the inside of the arm exposed to air during collection
69
69. Which electrolyte level best correlates with plasma osmolality? A. Sodium B. Chloride C. Bicarbonate D. Calcium
A. Sodium
70
70. Which formula is most accurate in predicting plasma osmolality? A. Na + 2(Cl) + BUN + glucose B. 2(Na) + 2(Cl) + glucose + urea C. 2(Na) + (glucose ÷ 18) + (BUN ÷ 2.8) D. Na + Cl + K + HCO3
C. 2(Na) + (glucose ÷ 18) + (BUN ÷ 2.8)