Conventional or physicochemical approach in intensive care unit patients with metabolic acidosis

Crit Care. 2003 Jun;7(3):R41-5. doi: 10.1186/cc2184. Epub 2003 May 1.


Introduction: Metabolic acidosis is the most frequent acid-base disorder in the intensive care unit. The optimal analysis of the underlying mechanisms is unknown.

Aim: To compare the conventional approach with the physicochemical approach in quantifying complicated metabolic acidosis in patients in the intensive care unit.

Patients and methods: We included 50 consecutive patients with a metabolic acidosis (standard base excess < or = -5). We measured sodium, potassium, calcium, magnesium, chloride, lactate, creatinine, urea, phosphate, albumin, pH, and arterial carbon dioxide and oxygen tensions in every patient. We then calculated HCO3-, the base excess, the anion gap, the albumin-corrected anion gap, the apparent strong ion difference, the effective strong ion difference and the strong ion gap.

Results: Most patients had multiple underlying mechanisms explaining the metabolic acidosis. Unmeasured strong anions were present in 98%, hyperchloremia was present in 80% and elevated lactate levels were present in 62% of patients. Calculation of the anion gap was not useful for the detection of hyperlactatemia. There was an excellent relation between the strong ion gap and the albumin-corrected and lactate-corrected anion gap (r2 = 0.934), with a bias of 1.86 and a precision of 0.96.

Conclusion: Multiple underlying mechanisms are present in most intensive care unit patients with a metabolic acidosis. These mechanisms are reliably determined by measuring the lactate-corrected and albumin-corrected anion gap. Calculation of the more time-consuming strong ion gap according to Stewart is therefore unnecessary.

Publication types

  • Clinical Trial
  • Comparative Study

MeSH terms

  • Acid-Base Equilibrium*
  • Acidosis / diagnosis
  • Acidosis / metabolism*
  • Acidosis / therapy*
  • Adult
  • Aged
  • Aged, 80 and over
  • Anions / blood
  • Blood Chemical Analysis / methods
  • Chlorides / blood
  • Female
  • Humans
  • Intensive Care Units*
  • Lactic Acid / blood
  • Male
  • Middle Aged
  • Process Assessment, Health Care


  • Anions
  • Chlorides
  • Lactic Acid