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For further information, see CMDT Part 21-17: Metabolic Acidosis

For further information, see CMDT Part 21-18: Increased Anion Gap Acidosis (Increased Unmeasured Anions)

Key Features

Essentials of Diagnosis

  • Decreased HCO3 with acidemia

  • Classified into increased anion gap acidosis and normal anion gap acidosis

  • Lactic acidosis, ketoacidosis, and toxins produce metabolic acidoses with the largest anion gaps

  • Normal anion gap acidosis is mainly caused by gastrointestinal HCO3 loss or RTA. Urinary anion gap may help distinguish between these causes

General Considerations

  • Calculation of the anion gap is useful in determining the cause of the metabolic acidosis

  • Normochloremic (increased anion gap) metabolic acidosis

    • Generally results from addition to the blood of organic acids such as lactate, acetoacetate, beta-hydroxybutyrate, and exogenous toxins

    • Other anions such as isocitrate, alpha-ketoglutarate, malate, and D-lactate may contribute to the anion gap of lactic acidosis, diabetic ketoacidosis (DKA), and acidosis of unknown etiology

    • Uremia creates an increased anion gap metabolic acidosis from unexcreted organic acids and anions (Table 21–13)

Table 21–13.Common causes and therapy for increased anion gap metabolic acidosis.

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