Background: A true “ion gap” does not exist in vivo which
makes the anion gap a fundamental tool to evaluate acid-base disorders. The
strong anion gap (SIG), which is the foundation of the Stewart acid-base
method, is a term that many doctors are unaware of, despite its significance in
understanding acid-base pathophysiology. It is unknown how much the anion gap
and the strong ion gap differ quantitatively.
Aim: The present study aimed to discuss narrowing the gap
between the anion gap and the strong ion gap.
Methods: The quantitative difference between the SIG and the
albumin-corrected anion gap (AGc) was calculated at a wide range of albumin,
phosphorus and pH levels.
Results: At an albumin level of 1-3 g/dl and pH from
6.9-7.3, the contribution difference of albumin between the AGc and the SIG was
maximally -0.97 to 0.51 mEq/L. In metabolic alkalosis and hypoalbuminaemia, the
AGc differed less than 2 mEq/L from the SIG. The calculated contribution of
phosphorus was higher in the SIG with phosphorus levels > 2 mmol/L and could
be accounted for in the anion gap with the conversion factor 1.76x[phosphorus,
in mmol/L].
Conclusion: The SIG and the AGc were nearly identical across
a wide range of values, particularly when albumin and phosphorus levels were
low. The anion gap would be more precise incorporating the major components of
the SIG using the equation: [Na+] - [Cl-] - [HCO3-] - 2.5x[albumin, in g/dL] –
1.76x[phosphorus, in mmol/L], with an arbitrarily set reference range of 1 + 5
mEq/L. To have a better understanding of the pathophysiology and to be more
accurate, the anion gap, or perhaps a more logical term, “the ion gap” should
be written to become almost identical to the SIG.
Author(s) Details
Kenrick Berend
Department of Nephrology, Curacao Medical Centre, Curacao.
Andrew L. Lundquist
Division of Nephrology, Massachusetts General Hospital,
Boston, MA, United States.
Please see the link:- https://doi.org/10.9734/bpi/mria/v10/998
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