Metabolic Acidosis

Question 1

Metabolic acidosis: Classification

Answer 1

According to anion gap >>>

• Metabolic acidosis >> normal anion gap
• Metabolic acidosis >> raised anion gap

​Metabolic acidosis due to high lactate levels >> can be further sub-divided into 2:

• Lactic acidosis type A
• Lactic acidosis type B

Question 2

Anion gap: calculation

Answer 2

(Na + K) - (Cl + HCO₃)

Question 3

Anion gap: normal range

OR Normal anion gap

Answer 3

10-18mmol/L

Question 4

Question hint >> When to consider calculating anion gap?

Answer 4

If the queston supplies “chloride level” >> calculate anion gap

Question 5

Normal anion gap metabolic acidosis >> synonym

Answer 5

Hyperchloraemic metabolic acidosis

Question 6

Normal anion gap metabolic acidosis >> chlorine level

Answer 6

High (Hyperchloraemia)

Normal Cl level: 95-110mmol/L; here >110mmol/L

Question 7

Why is hyperchloraemia in “normal anion gap metabolic acidosis”?

Answer 7

Chloride is retained to balance the charge of HCO₃^- ions, which are lost

Question 8

Normal anion gap Metabolic acidosis >> Causes

Answer 8

• GI bicarbonate (HCO₃) loss
  
  • Diarrhoea
  • Ureterosigmoidostomy
  • Fistula (e.g. pancreatic)
• Renal bicarbonate (HCO₃) loss
  
  • RTA (Renal tubular acidosis) type 2 (Proximal)
  • Drugs:
    
    • Acetazolamide
    • Allopurinol
    • Benzylpenicillin
    • Diclofenac
  • ​Tubular damage
  • Hyperparathyroidism
• ​Reduced H⁺ ion secretion from the kidneys
  
  • RTA type 1 (Distal)
  • RTA type 4
• Ammonium chloride injection (NH₄Cl)
• Addison’s disease (hyperkalaemia >> met. acidosis)

Question 9

Metabolic acidosis + normal anion gap + hypokalaemia >>> causes

Answer 9

• Diarrhoea
• RTA (Renal tubular acidosis) type 1,2,3
• Acetozolamide

Question 10

Metabolic acidosis + normal anion gap + hyperkalaemia >>> cause

Answer 10

• Addison’s disease
• RTA (Renal tubular acidosis) type 4

Question 11

Renal tubular acidosis >> anion gap

OR

Anion gap in RTA (Renal tubular acidosis)

Answer 11

Normal

Question 12

Raised anion gap metabolic acidosis >> causes

Answer 12

• Lactate >> high (Lactic acidosis)
  
  • type A: shock, hypoxia, burns
  • type B: Metformin, FeSO₄ (iron)
• Ketones >> high
  
  • DKA
  • Alcohol
• Urate >> high
  
  • Renal failure
• Acid poisoning
  
  • Salicylates (Aspirin) >>> metabolic acidosis with respiratory alkalosis
  • Methanol

Question 13

Metabolic acidosis due to high lactate levels >> Classification

OR

Lactic acidosis >> Classification

Answer 13

• Type A: shock, hypoxia, burns
• Type B: Metformin, FeSO4 (iron)

Question 14

Metabolic acidosis >> K level

Answer 14

Hyperkalaemia (mainly)

few cases (4) can have hypokalaemia

Question 15

Metabolic acidosis + hypokalaemia >>> Causes

Answer 15

• Diarrhoea (hypercholraemic met. acidosis, normal anion gap)
• Renal tubular acidosis type 1, 2, 3 (hypercholraemic met. acidosis, normal anion gap)
• Acetazolamide drug (hypercholraemic met. acidosis, normal anion gap)
• Partially treated DKA (raised anion gap)

​Except these 4 exceptional causes >> all metabolic acidosis are related to hyperkalaemia

Question 16

ABG level in metabolic acidosis (uncompensated)

Answer 16

• pH >>> Low (H⁺ >>> High)
• HCO₃ >>> Low
• pCO₂ >>> Normal (Low if its compensatory)

Question 17

ABG level in metabolic acidosis (partially compensated)

Answer 17

• pH >>> Low (H+ >>> High)
• HCO₃ >>> Low
• pCO₂ >>> Low

Question 18

ABG level in fully compensated metabolic acidosis

Answer 18

• pH >>> Normal (H+ >>> Normal)
• HCO₃ >>> Low
• pCO₂ >>> Low

Question 19

Metabolic acidosis is compensated by -?

Answer 19

Respiratory system (CO₂ goes down)

Question 20

Metabolic acidosis + respiratory alkalosis >>> cause?

Answer 20

Salicylate (e.g. Aspirin) poisoning