Acidosis MCQs With Answer

Acidosis MCQs With Answer for B. Pharm students offers a concise, Student-friendly post to acid-base disorders, emphasizing clinical relevance and pharmacological management. This resource covers metabolic and respiratory acidosis, anion gap calculation, ABG interpretation, compensatory mechanisms, common drug-induced causes, and therapeutic approaches including bicarbonate therapy and dialysis. Tailored for B. Pharm learners, the questions reinforce core concepts such as Henderson-Hasselbalch application, Winter’s formula, delta gap, and differential diagnosis of high vs normal anion gap acidosis. Practical focus on drugs (metformin, acetazolamide, salicylates) and lab interpretation helps prepare for exams and clinical practice. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What primary disturbance defines metabolic acidosis?

• Decrease in serum bicarbonate (HCO3−)
• Increase in PaCO2
• Increase in serum bicarbonate (HCO3−)
• Decrease in PaO2

Correct Answer: Decrease in serum bicarbonate (HCO3−)

Q2. Which arterial blood gas pattern is typical of respiratory acidosis?

• Low PaCO2 with low HCO3−
• High PaCO2 with elevated HCO3− (in chronic cases)
• Normal PaCO2 with low HCO3−
• High PaO2 with low HCO3−

Correct Answer: High PaCO2 with elevated HCO3− (in chronic cases)

Q3. Which formula estimates expected respiratory compensation in metabolic acidosis (acute)?

• Winter’s formula: PaCO2 = 1.5 × HCO3− + 8 ± 2
• Henderson-Hasselbalch: pH = pKa + log [HCO3−]/(0.03 × PaCO2)
• Expected PaCO2 = 40 − (1 × HCO3−)
• PaCO2 = 2 × HCO3−

Correct Answer: Winter’s formula: PaCO2 = 1.5 × HCO3− + 8 ± 2

Q4. A high anion gap metabolic acidosis indicates accumulation of which?

• Unmeasured anions such as lactate, ketoacids, or toxins
• Excess chloride ions only
• Increased bicarbonate buffer
• Elevated serum albumin exclusively

Correct Answer: Unmeasured anions such as lactate, ketoacids, or toxins

Q5. How is the anion gap calculated (simplest common formula)?

• [Na+] − ([Cl−] + [HCO3−])
• [K+] + [Na+] + [Cl−]
• [HCO3−] − [Cl−]
• [Na+] + [Cl−] − [HCO3−]

Correct Answer: [Na+] − ([Cl−] + [HCO3−])

Q6. Which condition most commonly causes high anion gap metabolic acidosis?

• Diabetic ketoacidosis (DKA)
• Hyperaldosteronism
• Vomiting
• Primary hyperparathyroidism

Correct Answer: Diabetic ketoacidosis (DKA)

Q7. Which drug is associated with lactic acidosis, particularly in renal impairment?

• Metformin
• Propranolol
• Furosemide
• Warfarin

Correct Answer: Metformin

Q8. What is a common cause of normal anion gap (hyperchloremic) metabolic acidosis?

• Diarrhea with bicarbonate loss
• Lactic acidosis from shock
• Ethylene glycol poisoning
• Diabetic ketoacidosis

Correct Answer: Diarrhea with bicarbonate loss

Q9. Which renal tubular disorder causes proximal (type 2) renal tubular acidosis?

• Defect in proximal bicarbonate reabsorption
• Failure of distal H+ secretion
• Excess aldosterone activity
• Increased ammonium excretion

Correct Answer: Defect in proximal bicarbonate reabsorption

Q10. Distal (type 1) renal tubular acidosis is characterized by:

• Impaired H+ secretion in the distal nephron causing hypokalemia and inability to acidify urine
• Excess bicarbonate reabsorption leading to alkalosis
• Increased ammoniagenesis with hyperkalemia
• Volume expansion due to sodium retention

Correct Answer: Impaired H+ secretion in the distal nephron causing hypokalemia and inability to acidify urine

Q11. In metabolic acidosis, how does the Henderson-Hasselbalch equation help?

• Relates pH to HCO3− and PaCO2, aiding interpretation and treatment decisions
• Directly measures serum lactate concentration
• Calculates urine pH from serum electrolytes
• Predicts oxygen saturation solely

Correct Answer: Relates pH to HCO3− and PaCO2, aiding interpretation and treatment decisions

Q12. Which measurement helps distinguish renal from gastrointestinal causes of normal anion gap acidosis?

• Urine anion gap (UAG)
• Serum troponin
• Serum bilirubin
• Urine glucose

Correct Answer: Urine anion gap (UAG)

Q13. A negative urine anion gap suggests which mechanism in metabolic acidosis?

• Extrarenal loss of bicarbonate with appropriate renal ammonium excretion
• Renal tubular acidosis with low ammonium excretion
• Primary respiratory acidosis
• Excessive chloride retention in the kidney

Correct Answer: Extrarenal loss of bicarbonate with appropriate renal ammonium excretion

Q14. Which intoxication typically produces high anion gap metabolic acidosis with an elevated osmolar gap?

• Ethylene glycol poisoning
• Acetaminophen overdose
• Beta blocker overdose
• Iron poisoning

Correct Answer: Ethylene glycol poisoning

Q15. How does salicylate toxicity produce acid-base disturbance?

• Mixed respiratory alkalosis and metabolic acidosis
• Pure respiratory acidosis only
• Pure metabolic alkalosis only
• Isolated hyponatremia without acid-base change

Correct Answer: Mixed respiratory alkalosis and metabolic acidosis

Q16. Which laboratory finding indicates respiratory compensation in acute metabolic acidosis?

• Decreased PaCO2 according to Winter’s formula
• Increased PaCO2 above 60 mmHg
• Elevated PaO2 with no PaCO2 change
• Increased serum bicarbonate

Correct Answer: Decreased PaCO2 according to Winter’s formula

Q17. Which buffer system is the primary extracellular buffer in humans?

• Carbonic acid–bicarbonate (CO2/HCO3−) system
• Hemoglobin buffer exclusively
• Phosphate buffer only
• Protein buffer with no role of bicarbonate

Correct Answer: Carbonic acid–bicarbonate (CO2/HCO3−) system

Q18. Which drug can cause proximal renal tubular acidosis by interfering with carbonic anhydrase?

• Acetazolamide
• Spironolactone
• Amiloride
• Hydrochlorothiazide

Correct Answer: Acetazolamide

Q19. In diabetic ketoacidosis, initial therapy includes:

• IV fluids, insulin, and electrolyte correction (especially potassium)
• Immediate oral bicarbonate for all patients
• Loop diuretics to reduce volume
• High-dose corticosteroids as first-line

Correct Answer: IV fluids, insulin, and electrolyte correction (especially potassium)

Q20. What is the role of bicarbonate therapy in metabolic acidosis?

• Used selectively for severe acidemia (pH <7.1) or specific indications
• Required in all cases of metabolic acidosis
• Contraindicated in DKA always
• Only used to treat respiratory acidosis

Correct Answer: Used selectively for severe acidemia (pH <7.1) or specific indications

Q21. The delta gap assesses:

• Presence of mixed metabolic acid-base disorders using changes in anion gap and HCO3−
• Degree of respiratory compensation only
• Renal function via creatinine clearance
• Oxygen-carrying capacity of blood

Correct Answer: Presence of mixed metabolic acid-base disorders using changes in anion gap and HCO3−

Q22. Which lab value typically increases in lactic acidosis?

• Serum lactate concentration
• Serum bicarbonate concentration
• Arterial oxygen saturation
• Serum albumin concentration

Correct Answer: Serum lactate concentration

Q23. Methanol poisoning primarily causes toxicity by metabolism to:

• Formic acid, causing high anion gap metabolic acidosis and visual disturbance
• Ethylene glycol, causing nephrotoxicity
• Acetaldehyde causing hypoglycemia
• Lactic acid causing muscle cramps

Correct Answer: Formic acid, causing high anion gap metabolic acidosis and visual disturbance

Q24. Which therapy is specific for ethylene glycol and methanol poisoning?

• Ethanol or fomepizole to inhibit alcohol dehydrogenase
• Activated charcoal only
• High-dose naloxone
• Beta-blockers to reduce metabolism

Correct Answer: Ethanol or fomepizole to inhibit alcohol dehydrogenase

Q25. In metabolic acidosis with increased anion gap, which additional lab correction is important?

• Correcting anion gap for hypoalbuminemia
• Adjusting chloride for glucose levels
• Changing sodium for potassium levels
• Correcting bicarbonate for calcium

Correct Answer: Correcting anion gap for hypoalbuminemia

Q26. Which electrolyte abnormality commonly accompanies metabolic acidosis?

• Hyperkalemia due to extracellular shift of K+
• Severe hypercalcemia always
• Marked hypophosphatemia exclusively
• Persistent hypernatremia as a rule

Correct Answer: Hyperkalemia due to extracellular shift of K+

Q27. Winter’s formula is used to assess:

• Appropriate respiratory compensation in metabolic acidosis
• Renal compensation in respiratory acidosis
• Serum osmolarity in toxic ingestions
• Drug dosing in renal failure

Correct Answer: Appropriate respiratory compensation in metabolic acidosis

Q28. Mixed metabolic acidosis and respiratory acidosis may be suspected when:

• PaCO2 is higher than expected compensation for the measured HCO3−
• PaCO2 is lower than expected for compensation
• Anion gap is zero
• Serum sodium is extremely low only

Correct Answer: PaCO2 is higher than expected compensation for the measured HCO3−

Q29. Which of the following increases endogenous acid production leading to high anion gap acidosis?

• Severe tissue hypoxia causing lactic acidosis
• Hyperventilation causing hypocapnia
• Excess antacid ingestion
• Excessive bicarbonate administration

Correct Answer: Severe tissue hypoxia causing lactic acidosis

Q30. In acute respiratory acidosis, immediate treatment often focuses on:

• Improving ventilation to reduce PaCO2
• Administering IV bicarbonate as first-line
• Inducing hypoventilation
• Restricting oxygen delivery

Correct Answer: Improving ventilation to reduce PaCO2

Q31. Which pharmacologic agent can precipitate type 4 renal tubular acidosis by causing hyperkalemia?

• ACE inhibitors
• Loop diuretics
• Acetazolamide
• Insulin

Correct Answer: ACE inhibitors

Q32. The expected acute change in HCO3− per 10 mmHg rise in PaCO2 is approximately:

• 1 mEq/L increase in HCO3−
• 10 mEq/L decrease in HCO3−
• 5 mEq/L decrease in HCO3−
• No change in HCO3−

Correct Answer: 1 mEq/L increase in HCO3−

Q33. Which bedside finding supports metabolic acidosis clinically?

• Kussmaul respirations (deep, rapid breathing)
• Bradypnea with shallow breaths
• Fixed splitting of S2 heart sound
• Peripheral cyanosis without respiratory change

Correct Answer: Kussmaul respirations (deep, rapid breathing)

Q34. Which investigational value helps differentiate causes of high anion gap acidosis due to toxic alcohols?

• Serum osmolal gap (osmolar gap)
• Serum amylase only
• Urine ketones only
• Serum calcium only

Correct Answer: Serum osmolal gap (osmolar gap)

Q35. Which physiological process increases urinary ammonium (NH4+) excretion to compensate for chronic metabolic acidosis?

• Enhanced renal ammoniagenesis from glutamine
• Reduced renal blood flow only
• Decreased aldosterone secretion exclusively
• Inhibition of carbonic anhydrase as primary mechanism

Correct Answer: Enhanced renal ammoniagenesis from glutamine

Q36. What is a pharmacologic therapy used to treat severe metabolic acidosis refractory to medical therapy?

• Hemodialysis to remove acids and correct electrolytes
• Oral sodium bicarbonate in all acute cases
• Beta-agonists to increase ventilation
• ACE inhibitors to enhance renal acid excretion

Correct Answer: Hemodialysis to remove acids and correct electrolytes

Q37. Which of the following is true about chronic respiratory acidosis?

• Renal retention of HCO3− occurs over days to weeks, increasing HCO3−
• There is no renal compensation
• Acute hyperventilation corrects it immediately
• It causes permanent hypernatremia

Correct Answer: Renal retention of HCO3− occurs over days to weeks, increasing HCO3−

Q38. In a patient with metabolic acidosis and an anion gap of 30 mEq/L, HCO3− of 8 mEq/L and normal albumin, what does the delta gap help determine?

• Whether a concurrent metabolic alkalosis or normal AG acidosis is present
• Whether respiratory alkalosis is present only
• Renal clearance rate of bicarbonate
• Glomerular filtration rate directly

Correct Answer: Whether a concurrent metabolic alkalosis or normal AG acidosis is present

Q39. Which of the following medications reduces acid production by inhibiting lipolysis in DKA management adjunctively?

• Insulin (reduces ketone production by inhibiting lipolysis)
• Metformin
• Acetazolamide
• Spironolactone

Correct Answer: Insulin (reduces ketone production by inhibiting lipolysis)

Q40. Which acid-base disorder is suggested by pH 7.25, PaCO2 30 mmHg, HCO3− 12 mEq/L?

• Primary metabolic acidosis with respiratory compensation
• Primary respiratory acidosis without compensation
• Primary metabolic alkalosis
• Primary respiratory alkalosis

Correct Answer: Primary metabolic acidosis with respiratory compensation

Q41. Which lab change is expected in acute metabolic acidosis regarding calcium binding?

• Increased ionized (free) calcium due to decreased albumin binding in acidosis
• Decreased ionized calcium because of increased protein binding
• No change in ionized calcium
• Immediate hypermagnesemia instead

Correct Answer: Increased ionized (free) calcium due to decreased albumin binding in acidosis

Q42. Which condition is characterized by metabolic acidosis and an inappropriately high urine pH (>5.5)?

• Distal (type 1) renal tubular acidosis
• Proximal (type 2) renal tubular acidosis always
• Diarrhea-induced acidosis
• Lactic acidosis due to sepsis

Correct Answer: Distal (type 1) renal tubular acidosis

Q43. Correction of chronic respiratory acidosis shows which laboratory trend?

• Elevation of HCO3− to partially normalize pH
• Immediate decrease in HCO3− to normal
• Massive hyperchloremia without HCO3− change
• Large rise in serum albumin

Correct Answer: Elevation of HCO3− to partially normalize pH

Q44. Which pharmacologic antagonist is used to treat methanol toxicity by blocking formation of toxic metabolites?

• Fomepizole (alcohol dehydrogenase inhibitor)
• N-acetylcysteine
• Flumazenil
• Deferoxamine

Correct Answer: Fomepizole (alcohol dehydrogenase inhibitor)

Q45. Hyperchloremic metabolic acidosis is often associated with which fluid therapy?

• Excessive normal saline (0.9% NaCl) infusion
• Balanced crystalloids exclusively
• Colloid solutions only
• Hypertonic saline avoidance

Correct Answer: Excessive normal saline (0.9% NaCl) infusion

Q46. Which of the following is a hallmark of aspirin (salicylate) overdose in acid-base terms?

• Initial respiratory alkalosis followed by metabolic acidosis
• Pure metabolic alkalosis only
• Isolated respiratory acidosis without metabolic component
• Normal anion gap without mixed disturbance

Correct Answer: Initial respiratory alkalosis followed by metabolic acidosis

Q47. Correction factor for anion gap per 1 g/dL decrease in serum albumin is approximately:

• Add 2.5 mEq/L to anion gap for each 1 g/dL decrease in albumin
• Subtract 5 mEq/L per 1 g/dL decrease
• Multiply AG by 10 for each g/dL change
• No correction is necessary for albumin

Correct Answer: Add 2.5 mEq/L to anion gap for each 1 g/dL decrease in albumin

Q48. In chronic metabolic acidosis, which bone-related process may occur over time?

• Bone buffering with chronic calcium and phosphate loss leading to osteopenia
• Bone hypertrophy and increased density
• Immediate bone formation only
• No effect on bone mineral content

Correct Answer: Bone buffering with chronic calcium and phosphate loss leading to osteopenia

Q49. Which clinical intervention helps reduce acid load in severe DKA besides insulin?

• Volume repletion with isotonic saline to improve perfusion and reduce lactate generation
• Immediate diuresis with loop diuretics
• High-dose corticosteroids acutely
• Prolonged fasting

Correct Answer: Volume repletion with isotonic saline to improve perfusion and reduce lactate generation

Q50. For exam-focused ABG interpretation, which step is essential first?

• Assess pH to determine primary disorder (acidosis vs alkalosis)
• Immediately calculate anion gap without pH
• Start bicarbonate therapy before interpretation
• Ignore PaCO2 and only evaluate HCO3−

Correct Answer: Assess pH to determine primary disorder (acidosis vs alkalosis)

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