Advanced Pathophysiology: Acid-Base Balance Disorders (NURS 611)
2026 |Maryville
1. A patient presents with a pH of 7.22, pCO2 of 30 mmHg, and HCO3- of 12
mEq/L. Which of the following best describes this acid-base status?
A. Metabolic acidosis with partial respiratory compensation
B. Uncompensated respiratory acidosis
C. Metabolic alkalosis with respiratory acidosis
D. Compensated respiratory alkalosis
Answer: A
Rationale: The pH is acidic (<7.35), and the primary driver is the low bicarbonate (12
mEq/L). The pCO2 is below normal (35-45 mmHg), indicating the lungs are attempting to
compensate by blowing off CO2.
2. Which physiological mechanism explains the shift of potassium out of cells
during acute metabolic acidosis?
A. Hydrogen ions enter the cell and are exchanged for potassium ions to maintain electroneutrality
B. Potassium follows water out of the cell due to osmotic pressure
C. Insulin resistance increases, preventing potassium from entering cells
D. The Na+/K+ ATPase pump is stimulated by a low pH environment
Answer: A
Rationale: In metabolic acidosis, excess extracellular H+ ions move into the intracellular
space. To maintain electrical balance, intracellular K+ ions move into the extracellular fluid,
potentially causing hyperkalemia.
,3. A patient with chronic obstructive pulmonary disease (COPD) has a pH of
7.36, pCO2 of 55 mmHg, and HCO3- of 32 mEq/L. This is an example of:
A. Uncompensated metabolic acidosis
B. Partially compensated metabolic alkalosis
C. Acute respiratory failure
D. Fully compensated respiratory acidosis
Answer: D
Rationale: The pH is within normal limits (7.35-7.45) but on the acidic side. The pCO2 is
high, indicating respiratory acidosis, and the HCO3- is elevated, indicating the kidneys have
compensated over time.
4. Which of the following conditions is most likely to result in a High Anion Gap
Metabolic Acidosis (HAGMA)?
A. Severe diarrhea
B. Renal tubular acidosis
C. Diabetic ketoacidosis
D. Chronic laxative abuse
Answer: C
Rationale: HAGMA occurs when fixed acids (like ketoacids in DKA) are added to the blood.
Diarrhea and renal tubular acidosis typically cause Normal Anion Gap Metabolic Acidosis
(NAGMA) due to bicarbonate loss.
5. Winter’s Formula is specifically used to calculate the expected pCO2 in which
disorder?
A. Respiratory alkalosis
B. Metabolic alkalosis
C. Mixed respiratory acidosis
D. Metabolic acidosis
Answer: D
, Rationale: Winter’s Formula (Expected pCO2 = [1.5 x HCO3-] + 8 +/- 2) is used to
determine if the respiratory compensation in metabolic acidosis is appropriate.
6. A patient hyperventilating due to a panic attack is likely to demonstrate
which acid-base imbalance?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic alkalosis
D. Metabolic acidosis
Answer: B
Rationale: Hyperventilation causes excessive elimination of CO2, leading to a decrease in
pCO2 and an increase in blood pH.
7. The primary renal response to a state of chronic respiratory acidosis is:
A. Decreased excretion of ammonium (NH4+)
B. Retention of chloride ions
C. Increased excretion of bicarbonate
D. Increased reabsorption of bicarbonate (HCO3-) and excretion of H+
Answer: D
Rationale: To compensate for high CO2, the kidneys retain bicarbonate and increase the
secretion of hydrogen ions into the urine.
8. Why does hypokalemia often occur in a patient with metabolic alkalosis?
A. The kidneys excrete potassium to conserve sodium in exchange for chloride
B. Potassium is lost through the lungs during hypoventilation
C. Potassium moves into the cells as hydrogen ions move out to buffer the extracellular fluid
D. Alkalosis prevents potassium from being absorbed in the distal tubule
Answer: C
Rationale: In alkalosis, H+ moves out of cells to lower pH, and K+ moves into cells to
maintain electrical neutrality, leading to hypokalemia.
2026 |Maryville
1. A patient presents with a pH of 7.22, pCO2 of 30 mmHg, and HCO3- of 12
mEq/L. Which of the following best describes this acid-base status?
A. Metabolic acidosis with partial respiratory compensation
B. Uncompensated respiratory acidosis
C. Metabolic alkalosis with respiratory acidosis
D. Compensated respiratory alkalosis
Answer: A
Rationale: The pH is acidic (<7.35), and the primary driver is the low bicarbonate (12
mEq/L). The pCO2 is below normal (35-45 mmHg), indicating the lungs are attempting to
compensate by blowing off CO2.
2. Which physiological mechanism explains the shift of potassium out of cells
during acute metabolic acidosis?
A. Hydrogen ions enter the cell and are exchanged for potassium ions to maintain electroneutrality
B. Potassium follows water out of the cell due to osmotic pressure
C. Insulin resistance increases, preventing potassium from entering cells
D. The Na+/K+ ATPase pump is stimulated by a low pH environment
Answer: A
Rationale: In metabolic acidosis, excess extracellular H+ ions move into the intracellular
space. To maintain electrical balance, intracellular K+ ions move into the extracellular fluid,
potentially causing hyperkalemia.
,3. A patient with chronic obstructive pulmonary disease (COPD) has a pH of
7.36, pCO2 of 55 mmHg, and HCO3- of 32 mEq/L. This is an example of:
A. Uncompensated metabolic acidosis
B. Partially compensated metabolic alkalosis
C. Acute respiratory failure
D. Fully compensated respiratory acidosis
Answer: D
Rationale: The pH is within normal limits (7.35-7.45) but on the acidic side. The pCO2 is
high, indicating respiratory acidosis, and the HCO3- is elevated, indicating the kidneys have
compensated over time.
4. Which of the following conditions is most likely to result in a High Anion Gap
Metabolic Acidosis (HAGMA)?
A. Severe diarrhea
B. Renal tubular acidosis
C. Diabetic ketoacidosis
D. Chronic laxative abuse
Answer: C
Rationale: HAGMA occurs when fixed acids (like ketoacids in DKA) are added to the blood.
Diarrhea and renal tubular acidosis typically cause Normal Anion Gap Metabolic Acidosis
(NAGMA) due to bicarbonate loss.
5. Winter’s Formula is specifically used to calculate the expected pCO2 in which
disorder?
A. Respiratory alkalosis
B. Metabolic alkalosis
C. Mixed respiratory acidosis
D. Metabolic acidosis
Answer: D
, Rationale: Winter’s Formula (Expected pCO2 = [1.5 x HCO3-] + 8 +/- 2) is used to
determine if the respiratory compensation in metabolic acidosis is appropriate.
6. A patient hyperventilating due to a panic attack is likely to demonstrate
which acid-base imbalance?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic alkalosis
D. Metabolic acidosis
Answer: B
Rationale: Hyperventilation causes excessive elimination of CO2, leading to a decrease in
pCO2 and an increase in blood pH.
7. The primary renal response to a state of chronic respiratory acidosis is:
A. Decreased excretion of ammonium (NH4+)
B. Retention of chloride ions
C. Increased excretion of bicarbonate
D. Increased reabsorption of bicarbonate (HCO3-) and excretion of H+
Answer: D
Rationale: To compensate for high CO2, the kidneys retain bicarbonate and increase the
secretion of hydrogen ions into the urine.
8. Why does hypokalemia often occur in a patient with metabolic alkalosis?
A. The kidneys excrete potassium to conserve sodium in exchange for chloride
B. Potassium is lost through the lungs during hypoventilation
C. Potassium moves into the cells as hydrogen ions move out to buffer the extracellular fluid
D. Alkalosis prevents potassium from being absorbed in the distal tubule
Answer: C
Rationale: In alkalosis, H+ moves out of cells to lower pH, and K+ moves into cells to
maintain electrical neutrality, leading to hypokalemia.
