Clinical Chemistry-Blood Gases, pH, and Electrolytes Flashcards
1
Q
- 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)
2
Q
- 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
3
Q
- 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
4
Q
- 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
5
Q
- 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
6
Q
- 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
7
Q
- 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
8
Q
- Which of the following contributes the most to
the serum total CO2?
A. PCO2
B. dCO2
C. HCO3–
D. Carbonium ion
A
C. HCO3–
9
Q
- 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
10
Q
- 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
11
Q
- 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)
12
Q
- 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
13
Q
- 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
14
Q
- 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
15
Q
- 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
16
Q
- 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
17
Q
- What is the maximum recommended storage time
and temperature for an arterial blood gas sample
drawn in a plastic syringe?
A
D.
18
Q
- 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
19
Q
- 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
20
Q
- 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
21
Q
- Which of the following will shift the O2 dissociation
curve to the left?
A. Anemia
B. Hyperthermia
C. Hypercapnia
D. Alkalosis
A
D. Alkalosis
22
Q
- 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
23
Q
- 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
24
Q
- 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
25
Q
- 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
A. Bicarbonate deficiency
26
Q
- Which of the following disorders is associated
with lactate acidosis?
A. Diarrhea
B. Renal tubular acidosis
C. Hypoaldosteronism
D. Alcoholism
A
D. Alcoholism
27
Q
- 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
A. Hyperventilation
28
Q
- 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
A. Anxiety
29
Q
- Which of the following conditions is associated
with both metabolic and respiratory alkalosis?
A. Hyperchloremia
B. Hypernatremia
C. Hyperphosphatemia
D. Hypokalemia
A
D. Hypokalemia
30
Q
- In uncompensated metabolic acidosis, which of
the following will be normal?
A. Plasma bicarbonate
B. PCO2
C. p50
D. Total CO2
A
B. PCO2
31
Q
- Which of the following conditions is classified as
normochloremic acidosis?
A. Diabetic ketoacidosis
B. Chronic pulmonary obstruction
C. Uremic acidosis
D. Diarrhea
A
A. Diabetic ketoacidosis
32
Q
- 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
A. 15 mm Hg
33
Q
- 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
A
C. Hyperventilation
34
Q
- 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
A. Systematic errors can be detected earlier than
with two controls
35
Q
- 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
A
B. Correct electrode and instrument drift
36
Q
- In which condition would hypochloremia be
expected?
A. Respiratory alkalosis
B. Metabolic acidosis
C. Metabolic alkalosis
D. All of these options
A
C. Metabolic alkalosis
37
Q
- 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
A
B. 20 mmol/L
38
Q
- Which of the following conditions will cause an
increased anion gap?
A. Diarrhea
B. Hypoaldosteronism
C. Hyperkalemia
D. Renal failure
A
D. Renal failure
39
Q
- 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
A. Depletion of cellular NAD+
40
Q
- 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
A. Hyperventilation
41
Q
- Which condition can result in acidosis?
A. Cystic fibrosis
B. Vomiting
C. Hyperaldosteronism
D. Excessive O2 therapy
A
D. Excessive O2 therapy
42
Q
- 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
A
D. Malignancy
43
Q
- 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
A. Low calcium; high inorganic phosphorus Pi
44
Q
- Which of the following conditions is associated
with hypophosphatemia?
A. Rickets
B. Multiple myeloma
C. Renal failure
D. Hypervitaminosis D
A
A. Rickets
45
Q
- 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
A
D. High urine or serum N-telopeptide of
type 1 collagen
46
Q
- 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
A. Osteocalcin
47
Q
- 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
A
C. Decreased urinary excretion indicates a positive
response to treatment
48
Q
- 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
A
D. Vitamin D deficiency is a risk factor for
developing osteoporosis
49
Q
- 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
A
C. Testing should be for total vitamin D when
screening for deficiency
50
Q
- 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
A
C. Pi
51
Q
- 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
A. Rate of unreduced phosphomolybdate formation
at 340 nm
52
Q
- What is the percentage of serum calcium that is
ionized (Cai)?
A. 30%
B. 45%
C. 60%
D. 80%
A
B. 45%
53
Q
- 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
A
B. Assay of whole blood collected in sodium oxalate
54
Q
- Which of the following conditions is associated
with a low serum magnesium?
A. Addison’s disease
B. Hemolytic anemia
C. Hyperparathyroidism
D. Pancreatitis
A
D. Pancreatitis
55
Q
- 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
A
B. Adding 8-hydroxyquinoline
56
Q
- Which electrolyte measurement is least affected by
hemolysis?
A. Potassium
B. Calcium
C. Pi
D. Magnesium
A
B. Calcium
57
Q
- Which of the following conditions is associated
with hypokalemia?
A. Addison’s disease
B. Hemolytic anemia
C. Digoxin intoxication
D. Alkalosis
A
D. Alkalosis
58
Q
- 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
A
D. Digitalis overdose
59
Q
- 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
A
C. 2.5 mmol/L
60
Q
- Which electrolyte is least likely to be elevated in
renal failure?
A. Potassium
B. Magnesium
C. Inorganic phosphorus
D. Sodium
A
D. Sodium
61
Q
- 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
A
B. Hyperosmolar plasma
62
Q
- Which of the following conditions is associated
with hypernatremia?
A. Diabetes insipidus
B. Hypoaldosteronism
C. Burns
D. Diarrhea
A
A. Diabetes insipidus
63
Q
- 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
A
B. 160 mmol/L
64
Q
- Which of the following conditions is associated
with total body sodium excess?
A. Renal failure
B. Hyperthyroidism
C. Hypoparathyroidism
D. Diabetic ketoacidosis
A
A. Renal failure
65
Q
- Which of the following conditions is associated
with hyponatremia?
A. Diuretic therapy
B. Cushing’s syndrome
C. Diabetes insipidus
D. Nephrotic syndrome
A
A. Diuretic therapy
66
Q
- 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
A
C. Hypoalbuminemia causes low total calcium but
does not affect Cai
67
Q
- 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
A. Sweat chloride greater than 60 mmol/L
68
Q
- 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
A
C. Leaving the preweighed gauze on the inside
of the arm exposed to air during collection
69
Q
- Which electrolyte level best correlates with plasma
osmolality?
A. Sodium
B. Chloride
C. Bicarbonate
D. Calcium
A
A. Sodium
70
Q
- 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
A
C. 2(Na) + (glucose ÷ 18) + (BUN ÷ 2.8)
