Clinical Chemistry (Acid-Base Metabolism)

Question 1

Which is the most predominant buffer system in the body?

A. Bicarbonate/carbonic acid
B. Acetate/acetic acid
C. Phosphate/phosphorous acid
D. Hemoglobin

Question 2

The measurement of the pressure of dissolved CO2 (PCO2) in the blood is most closely associated with the concentration of what substance?

A. pH
B. Bicarbonate (HCOs)
C. Carbonic acid (H2CO3)
D. PO2

Question 3

What is the term that describes the sum of carbonic acid and bicarbonate in plasma?

A. Total CO2
B. Standard bicarbonate
C. Buffer base
D. Base excess

Question 4

To maintain a pH of 7.4 in plasma, it is necessary to maintain a

A. 10:1 ratio of bicarbonate to carbonic acid
B. 20:1 ratio of bicarbonate to carbonic acid
C. 1:20 ratio of bicarbonate to carbonic acid
D. 20:1 ratio of carbonic acid to bicarbonate

Question 5

In the plasma, an excess in the concentration of bicarbonate without a change in PCO2 from normal will result in what physiological state?

A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis

Question 6

Which of the following characterizes respiratory acidosis?

A. Excess of bicarbonate
B. Deficit of bicarbonate
C. Excess of dissolved carbon dioxide (PCO2)
D. Deficit of dissolved carbon dioxide (PCO2)

Question 7

What is the specimen of choice for analysis of acid-base disturbances involving pulmonary dysfunction in an adult?

A. Venous blood
B. Arterial blood
C. Capillary blood
D. Urine

Question 8

What is the anticoagulant of choice for blood gas analysis?

A. EDTA
B. Heparin
C. Sodium fluoride
D. Citrate

Question 9

If a blood gas specimen is left exposed to air, which of the following changes will occur?

A. PO2 and pH increase; PCO2 decreases
B. PO2 and pH decrease; PCO2 increases
C. PO2 increases; pH and PCO2 decrease
D. PO2 decreases; pH and PCO2 increase

Question 10

How would blood gas parameters change if a sealed specimen is left at room temperature for 2 or more hours?

A. PO2 increases, PCO2 increases, pH increases
B. PO2 decreases, PCO2 decreases, pH decreases
C. PO2 decreases, PCO2 increases, pH decreases
D. PO2 increases, PCO2 increases, pH decreases

Question 11

The bicarbonate ion concentration may be calculated from the total CO2 and PCO2 blood levels by using which of the following formulas?

A. 0.03 x (PCO2 - total CO2)
B. (total CO2 + 0.03) x PCO2
C. 0.03 x (total CO2 - PO2)
D. total CO2 - (0.03 x PCO2)

Question 12

In order to maintain electrical neutrality in the red blood cell, bicarbonate leaves the red blood cell and enters the plasma through an exchange mechanism with what electrolyte?

A. Sodium
B. Potassium
C. Chloride
D. Phosphate

Question 13

In acute diabetic ketoacidosis, which of the following laboratory findings would be expected?

A. Fasting blood glucose elevated, pH elevated, ketone bodies present
B. Fasting blood glucose elevated, pH low, ketone bodies present
C. Fasting blood glucose elevated, pH normal, ketone bodies absent
D. Fasting blood glucose decreased, pH low, ketone bodies absent

Question 14

Which of the following is a cause of metabolic alkalosis?

A. Late stage of salicylate poisoning
B. Uncontrolled diabetes mellitus
C. Renal failure
D. Excessive vomiting

Question 15

Which of the following statements is true about partially compensated respiratory alkalosis?

A. PCO2 is higher than normal.
B. HCO-3 is higher than normal.
C. More CO2 is eliminated through the lungs by hyperventilation.
D. Renal reabsorption of HCO-3 is decreased.

Question 16

Which is a compensatory mechanism in respiratory acidosis?

A. Hypoventilation
B. Decreased reabsorption of bicarbonate by the kidneys
C. Increased Na+/H+ exchange by the kidneys
D. Decreased ammonia formation by the kidneys

Question 17

Which of the following will cause a shift of the oxygen dissociation curve to the right, resulting in a decreased affinity of hemoglobin for O2?

A. Low plasma pH level
B. Low PCO2 level
C. Low concentration of 2,3-bisphosphoglycerate
D. Low temperature

Question 18

Which of the following statements about carbonic anhydrase (CA) is true?

A. Catalyzes conversion of CO2 and H2O to HHCO3 in red blood cells
B. Causes shift to the left in oxygen dissociation curve
C. Catalyzes formation of H2CO3 from CO2 and H2O in the tissues
D. Inactive in renal tubular cells

Question 19

Which of the following statements best describes “base excess”?

A. Primarily refers to carbonic acid concentration
B. Positive values reflect metabolic alkalosis.
C. Created through metabolism of carbohydrates
D. Negative values represent a respiratory imbalance.

Question 20

Given the following information, calculate the blood pH.

PCO2 = 44 mm Hg
Total CO2 = 29 mmol/L

A. 6.28
B. 6.76
C. 7.42
D. 7.44

Question 21

A 75-year-old woman comes to her physician complaining of abdominal pain. She says she has had a sore stomach for the last 3 weeks and has been taking increasing doses of antacid pills to control it. Now she is taking a box of pills a day. Blood gases are drawn with the following results:

pH = 7.49, PCO2 = 59 mm Hg,
HCO3 = 25 mmol/L.

What do these data indicate?

A. Metabolic alkalosis, partially compensated
B. Respiratory acidosis, uncompensated
C. A dual problem of acidosis
D. An error in one of the blood gas measurements

Question 22

A 24-year-old drug abuser is brought into the emergency department unconscious. He has shallow breaths, looks pale, and is “clammy.” Blood gases show the following results: pH = 7.29, PCO2 = 50 mmHg, HCOs = 25 mmol/L. What condition is indicated by these results?

A. Metabolic alkalosis, partially compensated
B. Respiratory acidosis, uncompensated
C. A dual problem of acidosis
D. An error in one of the blood gas measurements

Question 23

Blood gases are drawn on a 68-year-old asthmatic who was recently admitted for treatment of a kidney infection. Blood gas results are as follows: pH — 7.25, PCO2 = 56mmHg, HCO3 = 16 mmol/L . What condition is indicated by these results?

A. Metabolic alkalosis, partially compensated
B. Respiratory acidosis, uncompensated
C. A dual problem of acidosis
D. An error in one of the blood gas measurements

Question 24

A mother brings her daughter, a 22-year old medical technology student, to her physician. The patient is hyperventilating and has glossy eyes. The mother explains that her daughter is scheduled to take her final course exam the next morning. The patient had been running around frantically all day in a worried state and then started to breathe heavily. Blood gases are drawn in the office with the following results: pH = 7.58, PCO2 = 55 mm Hg, HCO3 =18 mmol/L. What do these data indicate?

A. Metabolic alkalosis, partially
compensated
B. Respiratory acidosis, uncompensated
C. A dual problem of acidosis
D. An error in one of the blood gas measurements