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Crit Care Med. 1998 Nov;26(11):1807-10.

Anion gap and hypoalbuminemia.

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  • 1Department of Medicine, St. Peter's Hospital, State University of New York, Albany, USA.

Abstract

OBJECTIVES:

To show how hypoalbuminemia lowers the anion gap, which can mask a significant gap acidosis; and to derive a correction factor for it.

DESIGN:

Observational study.

SETTING:

Intensive care unit in a university-affiliated hospital.

SUBJECTS:

Nine normal subjects and 152 critically ill patients (265 measurements).

INTERVENTIONS:

None.

MEASUREMENTS AND MAIN RESULTS:

Arterial blood samples analyzed for pH, PCO2, and concentrations of plasma electrolytes and proteins. Marked hypoalbuminemia was common among the critically ill patients: 49% of them had serum albumin concentration of <20 g/L. Each g/L decrease in serum albumin caused the observed anion gap to underestimate the total concentration of gap anions by 0.25 mEq/L (r2 = .94).

CONCLUSIONS:

The observed anion gap can be adjusted for the effect of abnormal serum albumin concentrations as follows: adjusted anion gap = observed anion gap + 0.25 x ([normal albumin] [observed albumin]), where albumin concentrations are in g/L; if given in g/dL, the factor is 2.5. This adjustment returns the anion gap to the familiar scale of values that apply when albumin concentration is normal.

Comment in

PMID:
9824071
[PubMed - indexed for MEDLINE]
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