Metabolic acidosis
- What is metabolic acidosis?
- What are the causes?
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Metabolic acidosis
What is metabolic acidosis?
Metabolic acidosis occurs when an acid other than carbonic acid (due to CO2 retention) accumulates in the body, resulting in a fall in the plasma bicarbonate.
* Davidson’s Principles and Practice of Medicine, 22nd edition Page 445
What are the causes of metabolic acidosis?
Causes of metabolic acidosis
| Disorder | Mechanism |
| A. Normal anion gap** | |
| Ingestion or infusion of inorganic acid | Therapeutic infusion of or poisoning with NH4Cl, HCl |
| Gastrointestinal HCO3 loss | Loss of HCO3 in diarrhoea, small bowel fistula, urinary diversion procedure |
| Renal tubular acidosis (RTA) | Urinary loss of HCO3 in proximal RTA; impaired tubular acid secretion in distal RTA |
| B. Increased anion gap | |
| Endogenous acid load | |
| Diabetic ketoacidosis | Accumulation of ketones1 with hyperglycaemia |
| Starvation ketosis | Accumulation of ketones without hyperglycaemia |
| Lactic acidosis | Shock, liver disease, drugs |
| Renal failure | Accumulation of organic acids |
| Exogenous acid load | |
| Aspirin poisoning | Accumulation of salicylate2 |
| Methanol poisoning | Accumulation of formate |
| Ethylene glycol poisoning | Accumulation of glycolate, oxalate |
1Ketones include acid anions acetoacetate and β-hydroxybutyrate2Salicylate poisoning is also associated with respiratory alkalosis due to direct ventilatory stimulation. |
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**Anion gap = Difference between the main measured cations (Na+ + K+) and the anions (Cl− + HCO3−). This ‘gap’ is normally around 12–16 mmol/L (12–16 meq/L)
* Davidson’s Principles and Practice of Medicine, 22nd edition Page 445