Review
Unmeasured anions in metabolic acidosis: unravelling the mystery
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* Corresponding author: Lui G Forni lui.forni@wash.nhs.uk
1 Department of Critical Care, Worthing Hospital, Worthing, West Sussex BN11 2DH, UK
2 Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex BN1 9PX, UK
3 Renal Laboratory, St Thomas' Hospital, London SE1 7EH, UK
Critical Care 2006, 10:220 doi:10.1186/cc4954
Published: 12 July 2006Abstract
In the critically ill, metabolic acidosis is a common observation and, in clinical practice, the cause of this derangement is often multi-factorial. Various measures are often employed to try and characterise the aetiology of metabolic acidosis, the most popular of which is the anion gap. The purpose of the anion gap can be perceived as a means by which the physician is alerted to the presence of unmeasured anions in plasma that contribute to the observed acidosis. In many cases, the causative ion may be easily identified, such as lactate, but often the causative ion(s) remain unidentified, even after exclusion of the 'classic' causes. We describe here the various attempts in the literature that have been made to address this observation and highlight recent studies that reveal potential sources of such hitherto unmeasured anions.