The anion gap is used to aid in the differential diagnosis of metabolic acidosis.

It is calculated by subtracting the chloride and bicarbonate levels from the sodium plus potassium levels.

Anion gap = ( +" target="_blank" >^*" target="_blank" >) - ( ^* ) (we can also say : Anion gap= ( ) - ( ^* ) and its normal value ranges between 8 and 16 mEq/L plasma )

Interpretation and causes

---

High anion gap

• Lactic acidosis
• Ketoacidosis
• Renal failure (Uremia)
• Iron
• INH
• Isopropolol
• Ingestions:
  • Salicylate
  • Ethanol
  • Methanol (formaldehyde)
  • Ethylene glycol
  • Paraldehyde
  • Toluene
  • Sulfur

Normal anion gap (hyperchloremic acidosis)

• Gastrointestinal loss of HCO_{3^{- (i.e. diarrhea)}}
• Renal loss of HCO_{3^{- (i.e. proximal renal tubular acidosis)}}
• Renal dysfunction (i.e. some cases of renal failure, hypoaldosteronism, distal renal tubular acidosis)
• Ingestions
  • Ammonium chloride
  • Hyperalimentation fluids (i.e. total parenteral nutrition)
• Some cases of ketoacidosis, particularly during insulin treatment

• Alcohol (such as ethanol) can effect anion gap by inducing alcohol dehydrogenase enzyme.

Low anion gap

A low anion gap is relatively rare but may occur from the presence of abnormal positively charged proteins, as in multiple myeloma, or in the setting of a low albumin level.

References

---

• Clinical Physiology of Acid-Base and Electrolyte Disorders by Rose, Post
• Intensive Care Medicine by Irwin and Rippe
• The ICU Book by Marino

Electrolyte disturbance | Intensive care medicine | Emergency medicine

Luka anionowa