Acid-Base Balance MCQs

**NCLEX-Style Acid-Base Balance MCQs** **1. A patient's arterial blood gas (ABG) results are: pH 7.30, PaCO₂ 50 mmHg, HCO₃⁻ 24 mEq/L. What is the correct interpretation?** a\) Metabolic acidosis\ b) Respiratory acidosis\ c) Metabolic alkalosis\ d) Respiratory alkalosis **Answer:** **b) Respirator...

**NCLEX-Style Acid-Base Balance MCQs** **1. A patient's arterial blood gas (ABG) results are: pH 7.30, PaCO₂ 50 mmHg, HCO₃⁻ 24 mEq/L. What is the correct interpretation?** a\) Metabolic acidosis\ b) Respiratory acidosis\ c) Metabolic alkalosis\ d) Respiratory alkalosis **Answer:** **b) Respiratory acidosis**\ **Rationale:** A decreased pH (\45 mmHg) with normal HCO₃⁻ suggests a respiratory origin. **2. Which of the following is a likely cause of respiratory acidosis?** a\) Hyperventilation\ b) Chronic obstructive pulmonary disease (COPD)\ c) Severe vomiting\ d) Diabetic ketoacidosis (DKA) **Answer:** **b) Chronic obstructive pulmonary disease (COPD)**\ **Rationale:** Hypoventilation, as seen in COPD, causes CO₂ retention, leading to respiratory acidosis. **3. Which symptom is most concerning in a patient with respiratory acidosis?** a\) Tingling in the extremities\ b) Bradycardia and hypotension\ c) Muscle cramping\ d) Increased urine output **Answer:** **b) Bradycardia and hypotension**\ **Rationale:** Severe acidosis can depress cardiac function, leading to bradycardia and hypotension. **4. A patient is hyperventilating due to anxiety. Which ABG findings would the nurse expect?** a\) pH 7.48, PaCO₂ 30 mmHg, HCO₃⁻ 24 mEq/L\ b) pH 7.30, PaCO₂ 50 mmHg, HCO₃⁻ 24 mEq/L\ c) pH 7.40, PaCO₂ 40 mmHg, HCO₃⁻ 24 mEq/L\ d) pH 7.35, PaCO₂ 35 mmHg, HCO₃⁻ 28 mEq/L **Answer:** **a) pH 7.48, PaCO₂ 30 mmHg, HCO₃⁻ 24 mEq/L**\ **Rationale:** Hyperventilation leads to respiratory alkalosis, characterized by increased pH and decreased PaCO₂. **5. What is the primary compensatory mechanism for metabolic acidosis?** a\) Decreasing respiratory rate\ b) Increasing bicarbonate reabsorption\ c) Hyperventilation\ d) Increasing urine output **Answer:** **c) Hyperventilation**\ **Rationale:** The lungs compensate by increasing CO₂ excretion through rapid breathing. **6. Which condition can cause metabolic acidosis?** a\) Excessive vomiting\ b) Salicylate poisoning\ c) Hypoventilation\ d) Pulmonary embolism **Answer:** **b) Salicylate poisoning**\ **Rationale:** Salicylates increase acid production, leading to metabolic acidosis. **7. A nurse is caring for a patient with metabolic alkalosis. Which intervention is appropriate?** a\) Encourage deep breathing\ b) Administer potassium supplements\ c) Administer sodium bicarbonate\ d) Restrict fluid intake **Answer:** **b) Administer potassium supplements**\ **Rationale:** Hypokalemia often accompanies metabolic alkalosis and requires correction. **8. Which of the following is a cause of metabolic alkalosis?** a\) Renal failure\ b) Diabetic ketoacidosis\ c) Prolonged vomiting\ d) Salicylate overdose **Answer:** **c) Prolonged vomiting**\ **Rationale:** Loss of gastric acid through vomiting increases bicarbonate concentration, leading to metabolic alkalosis. **9. A patient's ABG results show pH 7.38, PaCO₂ 52 mmHg, HCO₃⁻ 30 mEq/L. How should the nurse interpret this?** a\) Partially compensated respiratory acidosis\ b) Fully compensated respiratory acidosis\ c) Partially compensated metabolic alkalosis\ d) Uncompensated respiratory acidosis **Answer:** **b) Fully compensated respiratory acidosis**\ **Rationale:** The normal pH with increased PaCO₂ and increased HCO₃⁻ indicates full compensation. **10. What clinical finding is most indicative of metabolic acidosis?** a\) Kussmaul respirations\ b) Muscle spasms\ c) Bradypnea\ d) Hyperreflexia **Answer:** **a) Kussmaul respirations**\ **Rationale:** Deep, rapid breathing (Kussmaul respirations) is a hallmark of metabolic acidosis. **11. Which lab value supports a diagnosis of metabolic alkalosis?** a\) pH 7.30, PaCO₂ 50 mmHg, HCO₃⁻ 24 mEq/L\ b) pH 7.50, PaCO₂ 48 mmHg, HCO₃⁻ 32 mEq/L\ c) pH 7.38, PaCO₂ 40 mmHg, HCO₃⁻ 24 mEq/L\ d) pH 7.33, PaCO₂ 28 mmHg, HCO₃⁻ 18 mEq/L **Answer:** **b) pH 7.50, PaCO₂ 48 mmHg, HCO₃⁻ 32 mEq/L**\ **Rationale:** Increased pH and increased HCO₃⁻ indicate metabolic alkalosis. **12. Which statement is true regarding compensation in metabolic acidosis?** a\) The kidneys excrete more bicarbonate\ b) The lungs hypoventilate to retain CO₂\ c) The lungs hyperventilate to blow off CO₂\ d) The kidneys retain hydrogen ions **Answer:** **c) The lungs hyperventilate to blow off CO₂**\ **Rationale:** The lungs compensate by increasing CO₂ excretion. **13. Which of the following ABG values indicates partially compensated metabolic acidosis?** a\) pH 7.36, PaCO₂ 40 mmHg, HCO₃⁻ 24 mEq/L\ b) pH 7.29, PaCO₂ 30 mmHg, HCO₃⁻ 18 mEq/L\ c) pH 7.40, PaCO₂ 40 mmHg, HCO₃⁻ 24 mEq/L\ d) pH 7.48, PaCO₂ 42 mmHg, HCO₃⁻ 28 mEq/L **Answer:** **b) pH 7.29, PaCO₂ 30 mmHg, HCO₃⁻ 18 mEq/L**\ **Rationale:** The low pH confirms acidosis, the low HCO₃⁻ confirms metabolic origin, and the low PaCO₂ suggests partial respiratory compensation. **14. A patient with metabolic acidosis due to diabetic ketoacidosis (DKA) will most likely exhibit which ABG result?** a\) pH 7.52, PaCO₂ 48 mmHg, HCO₃⁻ 30 mEq/L\ b) pH 7.28, PaCO₂ 30 mmHg, HCO₃⁻ 18 mEq/L\ c) pH 7.38, PaCO₂ 40 mmHg, HCO₃⁻ 24 mEq/L\ d) pH 7.48, PaCO₂ 42 mmHg, HCO₃⁻ 28 mEq/L **Answer:** **b) pH 7.28, PaCO₂ 30 mmHg, HCO₃⁻ 18 mEq/L**\ **Rationale:** A decreased pH, decreased HCO₃⁻, and compensatory decrease in PaCO₂ indicate metabolic acidosis with respiratory compensation. **15. Which nursing intervention is appropriate for a patient with respiratory alkalosis due to hyperventilation?** a\) Encourage deep breathing\ b) Provide oxygen therapy\ c) Instruct the patient to breathe into a paper bag\ d) Administer sodium bicarbonate **Answer:** **c) Instruct the patient to breathe into a paper bag**\ **Rationale:** Breathing into a paper bag increases CO₂ levels, helping correct respiratory alkalosis caused by hyperventilation. **16. Which condition is most likely to cause metabolic alkalosis?** a\) Diabetic ketoacidosis (DKA)\ b) Severe diarrhea\ c) Nasogastric suctioning\ d) COPD **Answer:** **c) Nasogastric suctioning**\ **Rationale:** The loss of gastric acid through suctioning or vomiting can lead to metabolic alkalosis. **17. A nurse is evaluating the ABG results of a patient who has a pH of 7.31, PaCO₂ of 40 mmHg, and HCO₃⁻ of 18 mEq/L. What is the correct interpretation?** a\) Respiratory acidosis\ b) Respiratory alkalosis\ c) Metabolic acidosis\ d) Metabolic alkalosis **Answer:** **c) Metabolic acidosis**\ **Rationale:** The low pH and decreased HCO₃⁻ indicate metabolic acidosis. **18. A patient's ABG values are: pH 7.45, PaCO₂ 30 mmHg, HCO₃⁻ 20 mEq/L. How should the nurse interpret this?** a\) Partially compensated metabolic acidosis\ b) Fully compensated respiratory alkalosis\ c) Partially compensated respiratory acidosis\ d) Uncompensated metabolic alkalosis **Answer:** **b) Fully compensated respiratory alkalosis**\ **Rationale:** The pH is normal but on the alkaline side, the PaCO₂ is low, and the HCO₃⁻ is low, indicating full compensation. **19. A patient with metabolic acidosis due to renal failure is receiving sodium bicarbonate therapy. What is the priority nursing assessment?** a\) Monitor for signs of hypoventilation\ b) Monitor for signs of hyperkalemia\ c) Assess for symptoms of fluid overload\ d) Monitor for signs of respiratory depression **Answer:** **c) Assess for symptoms of fluid overload**\ **Rationale:** Sodium bicarbonate therapy can cause fluid overload due to sodium retention. **20. Which of the following conditions can cause respiratory alkalosis?** a\) Pulmonary embolism\ b) Acute respiratory failure\ c) Opiate overdose\ d) Chronic lung disease **Answer:** **a) Pulmonary embolism**\ **Rationale:** A pulmonary embolism can lead to hyperventilation, resulting in CO₂ loss and respiratory alkalosis.