Thursday, January 17, 2013

Adjustment of the Anion Gap for Changes in Serum Protein in Dogs and Cats


Adjustment of the Anion Gap for Changes in Serum Protein in Dogs and Cats
International Veterinary Emergency and Critical Care Symposium 2010
G. Hayes; K. Mathews; A. Bersenas; C. Dewey
University of Guelph, Guelph, ON, Canada
20446262
Introduction
An elevated anion gap (AG) in metabolic acidosis is suggestive of hyperlactemia, ketoacidosis, renal failure, or toxicity. Because blood proteins carry a negative charge, the AG is reduced in hypoproteinemia, and a diagnosis of high AG acidosis may be missed. There is a need for the development of AG adjustment formulas in dogs and cats, derived from populations that include hypoproteinemic patients.
Methods
This was a retrospective observational study, evaluating serum samples from 2161 feline and 8952 canine patients. Serum albumin, total protein (TP), electrolytes, phosphate and bicarbonate were measured in patients of varying ages with a range of clinical problems. Linear regression analysis was used to assess the relationships between changes in serum total protein and albumin and AG. The impact of acidosis and hyperphosphatemia on these relationships was also assessed.
Results
Hypoalbuminemia was identified in 16% of canine and 22% of feline samples. Hypoalbuminemia and hypoproteinemia were associated with decreased AG in both canine and feline patients. Each decrease in TP of 1g/L was associated with a decrease in AG of 0.1 mmol/L in cats and 0.16 mmol/L in dogs. The relationship between serum TP and AG was not altered by the presence of acidosis or hyperphosphatemia. Each decrease in albumin of 1g/L was associated with a decrease in AG of 0.17mmol/L in cats and 0.29 mmol in acidotic dogs when serum albumin <= 40g/L.
Conclusion
AG is altered in both species by changes in serum protein levels. Adjustment formulas are presented to allow rapid calculation of AGadjusted.

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