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. 2003 May;88(5):419–422. doi: 10.1136/adc.88.5.419

Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap

A Durward 1, A Mayer 1, S Skellett 1, D Taylor 1, S Hanna 1, S Tibby 1, I Murdoch 1
PMCID: PMC1719575  PMID: 12716714

Abstract

Aims: Hypoalbuminaemia has significance in adult critical illness as an independent predictor of mortality. In addition, the anion gap is predominantly due to the negative charge of albumin, thus hypoalbuminaemia may lead to its underestimation. We examine this phenomenon in critically ill children, documenting the incidence, early evolution, and prognosis of hypoalbuminaemia (<33 g/l), and quantify its influence on the anion gap.

Methods: Prospective descriptive study of 134 critically ill children in the paediatric intensive care unit (ICU). Paired arterial blood samples were taken at ICU admission and 24 hours later, from which blood gases, electrolytes, and albumin were measured. The anion gap (including potassium) was calculated and then corrected for albumin using Figge's formula.

Results: The incidence of admission hypoalbuminaemia was 57%, increasing to 76% at 24 hours. Neither admission hypoalbuminaemia, nor extreme hypoalbuminaemia (<20 g/l) predicted mortality; however, there was an association with increased median ICU stay (4.9 v 3.6 days). After correction for albumin the incidence of a raised anion gap (>18 mEq/l) increased from 28% to 44% in all samples (n = 263); this discrepancy was more pronounced in the 103 samples with metabolic acidosis (38% v 73%). Correction produced an average increase in the anion gap of 2.7 mEq/l (mean bias), with limits of agreement of ±3.7 mEq/l.

Conclusion: Admission hypoalbuminaemia is common in critical illness, but is not an independent predictor of mortality. However, failure to correct the anion gap for albumin may underestimate the true anion gap, producing error in the interpretation of acid-base abnormalities. This may have treatment implications.

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Figure 1.

Figure 1

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Histogram of admission serum albumin concentration for all patients (n = 134). Lines indicate cut off values for normal albumin concentration (solid line), hypoalbuminaemia (dashed line), and extreme hypoalbuminaemia (dashed-dotted line).

Figure 2.

Figure 2

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Temporal profile of patients with (n = 76) and without admission hypoalbuminaemia (n = 58). *One death and three discharges from PICU before 24 hours; **one discharge from PICU before 24 hours.

Figure 3.

Figure 3

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Bland Altman plot for all samples (n = 263) comparing the corrected (AGcorr) and uncorrected anion gap (AG). Solid line represents the mean bias (2.7 mEq/l), dotted lines represent limits of agreement (-1.0 to 6.4 mEq/l).

Figure 4.

Figure 4

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Regression plot for the serum albumin concentration and albumin charge derived from Stewart's strong ion theory. The slope of the line is 0.27. Dotted lines represent 95% confidence intervals.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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