Question 1

An individual with an asthma attack; has the following data: pH = 7.32; [HCO₃⁻] = 25 mEq/L; partial pressure of carbon dioxide (Pco₂)= 50 mm Hg.Which acid-base disturbance is consistent with this clinical scenario and these arterial blood gas measurements?

A)Metabolic acidosis with respiratory compensation
B)Metabolic alkalosis with respiratory compensation
C)Respiratory acidosis with renal compensation (chronic respiratory acidosis)
D)Respiratory acidosis without renal compensation (acute respiratory acidosis)
E)Metabolic acidosis and respiratory acidosis

Accepted Answer

The low pH and elevated partial pressure of carbon dioxide indicate respiratory acidosis. The normal bicarbonate level suggests that the kidneys have not compensated for this, so it is acute respiratory acidosis. There is no evidence of an alkaline pH or high bicarbonate level suggestive of metabolic compensation.

Question 2

In response to metabolic acidosis,the kidneys increase the excretion of net acid.Which of the following is the most important component of this compensatory response? A)Increased filtered load of HCO₃⁻ B)Enhanced reabsorption of HCO₃⁻ by the proximal tubule C)Increased synthesis and excretion of NH₄⁺ D)Reduced H⁺ secretion by the distal tubule and collecting duct E)Reduced secretion of HCO₃⁻ by the collecting duct

Accepted Answer

The kidneys respond to metabolic acidosis by increasing the synthesis and excretion of ammonium (NH4+), which helps to remove excess hydrogen ions and regenerate bicarbonate, thus compensating for the acidosis.

Question 3

A 6-year-old boy presents to the emergency department with fever,abdominal cramps,and diarrhea.Arterial blood gas measurements are as follows: pH: 7.28 (normal: 7.35 to 7.45)
Pco₂: 24 mm Hg (normal: 33 to 44 mm Hg)
[HCO₃⁻]: 11 mEq/L (normal: 22 to 28 mEq/L)
What is the acid-base disorder?

A)Metabolic acidosis with respiratory compensation
B)Metabolic acidosis with respiratory acidosis
C)Acute respiratory acidosis
D)Chronic respiratory acidosis

Accepted Answer

The low pH and low bicarbonate (HC03) levels indicate metabolic acidosis. The low Pco2 suggests respiratory compensation. Therefore, the acid-base disorder is metabolic acidosis with respiratory compensation.

Question 4

An individual with a 20-year history of smoking three packs/day who has emphysema has the following data: pH = 7.37; [HCO₃⁻] = 28 mEq/L; Pco₂ = 50 mm Hg.Which acid-base disturbance is consistent with this clinical scenario and these arterial blood gas measurements?

A)Metabolic acidosis with respiratory compensation
B)Metabolic alkalosis with respiratory compensation
C)Respiratory acidosis with renal compensation (chronic respiratory acidosis)
D)Respiratory acidosis without renal compensation (acute respiratory acidosis)
E)Metabolic acidosis and respiratory acidosis

Accepted Answer

The arterial blood gas measurements indicate a slightly elevated bicarbonate level ([HCO3-] = 28 mEq/L) and an elevated partial pressure of carbon dioxide (Pco2 = 50 mm Hg) with a normal pH (7.37), suggesting that the individual has respiratory acidosis due to impaired gas exchange (common in emphysema) with renal compensation (evidenced by the elevated bicarbonate level to buffer the acidosis), making it chronic respiratory acidosis.

Question 5

An individual with diabetes mellitus who forgets to take insulin has the following data: pH = 7.29; [HCO₃⁻] = 12 mEq/L; Pco₂ = 26 mm Hg.Which acid-base disturbance is consistent with this clinical scenario and these arterial blood gas measurements?

A)Metabolic acidosis with respiratory compensation
B)Metabolic alkalosis with respiratory compensation
C)Respiratory acidosis with renal compensation (chronic respiratory acidosis)
D)Respiratory acidosis without renal compensation (acute respiratory acidosis)
E)Metabolic acidosis and respiratory acidosis

Accepted Answer

The data shows a low pH (7.29), indicating acidemia. The low bicarbonate ([HCO3-] = 12 mEq/L) suggests a primary metabolic acidosis. The decreased Pco2 (26 mm Hg) is consistent with respiratory compensation for the metabolic acidosis. This pattern is typical in diabetic ketoacidosis, where insulin deficiency leads to increased ketone production and acidosis, with compensatory hyperventilation to blow off CO2.

Question 6

An individual with cardiopulmonary arrest has the following data: pH = 6.85; [HCO₃⁻] = 10 mEq/L; Pco₂ = 60 mm Hg.Which acid-base disturbance is consistent with this clinical scenario and these arterial blood gas measurements?

A)Metabolic acidosis with respiratory compensation
B)Metabolic alkalosis with respiratory compensation
C)Respiratory acidosis with renal compensation (chronic respiratory acidosis)
D)Respiratory acidosis without renal compensation (acute respiratory acidosis)
E)Metabolic acidosis and respiratory acidosis

Accepted Answer

The individual's data shows a very low pH (6.85), indicating a strong acidemia. The bicarbonate level ([HCO3-] = 10 mEq/L) is significantly reduced, suggesting a metabolic acidosis. The elevated Pco2 (60 mm Hg) indicates hypoventilation and respiratory acidosis. Therefore, both metabolic and respiratory acidosis are present, making option E correct.

Question 7

An individual with a gastric ulcer who ingests large quantities of antacids has the following data: pH = 7.45; [HCO₃⁻] = 30 mEq/L; Pco₂ = 45 mm Hg.Which acid-base disturbance is consistent with this clinical scenario and these arterial blood gas measurements?

A)Metabolic acidosis with respiratory compensation
B)Metabolic alkalosis with respiratory compensation
C)Tespiratory acidosis with renal compensation (chronic respiratory acidosis)
D)Respiratory acidosis without renal compensation (acute respiratory acidosis)
E)Metabolic acidosis and respiratory acidosis

Accepted Answer

The high concentration of antacids could lead to metabolic alkalosis due to excess bicarbonate intake. The arterial blood gas measurements show respiratory compensation, with a pH within normal range and a slightly elevated Pco2, indicating compensation through hypoventilation. This is consistent with the clinical scenario of a gastric ulcer patient taking large amounts of antacids.

Question 8

A 60-year-old woman comes to the emergency department with shortness of breath.An arterial blood sample is obtained,and the following data are noted: Partial pressure of oxygen (Po₂): 75 mm Hg (normal: 75 to 100 mm Hg)
Pco₂: 58 mm Hg (normal: 33 to 44 mm Hg)
[HCO₃⁻]: 24 mEq/L (normal: 22 to 28 mEq/L)
PH: 7.24 (normal: 7.35 to 7.45)
What is the acid-base disorder?

A)Metabolic acidosis
B)Metabolic alkalosis
C)Acute respiratory acidosis
D)Acute respiratory alkalosis
E)Chronic respiratory acidosis

Accepted Answer

The pH is low, indicating acidemia. The Pco2 is elevated, indicating respiratory acidosis. The HCO3- is not out of the normal range, so there is no evidence of metabolic compensation.

Question 9

During a 24-hour period,an individual excretes in the urine 60 mmol of NH₄⁺,40 mmol of titratable acid,and 10 mmol of HCO₃⁻.If this individual is in acid-base balance,how much nonvolatile acid was produced from metabolism?

A)80 mmol/day
B)90 mmol/day
C)100 mmol/day
D)110 mmol/day
E)120 mmol/day

Accepted Answer

According to the law of conservation of mass, the amount of acid produced from metabolism should equal the amount of acid excreted in the urine (titratable acid + ammonium ion). Therefore, nonvolatile acid produced from metabolism = titratable acid + ammonium ion = 40 mmol + 60 mmol = 100 mmol/day. The amount of HCO₃⁻ excreted in the urine is not relevant for the calculation of nonvolatile acid production.

Deck 37: Role of the Kidneys in the Regulation of Acid-Base Balance