The anion gap as a prognostic indicator in horses with abdominal pain.

The research evaluates how the anion gap, a measure derived from electrolyte concentrations in the blood, can be used to predict survival rates in horses suffering from abdominal pain.

Introduction

• The study focuses on the anion gap in horses, which is a blood test that measures the difference between the detected anions (negatively charged ions) and cations (positively charged ions), specifically sodium and a combination of chloride and bicarbonate.
• The anion gap is not usually applied as a direct diagnostic tool to identify the source of abdominal pain, but it has potential as a prognostic indicator, a tool that predicts the likely progression or outcome of a disease.

Methodology

• Research involved analyzing the anion gap in 90 horses that displayed signs of abdominal pain, with laboratory data obtained shortly after their admission.
• The anion gap for every horse was calculated, where anion gap was defined as the difference between the concentration of sodium, and the sum of chloride and bicarbonate concentrations (all in milliequivalents per liter).

Findings

• The results showed a clear relationship between increases in anion gap and decreases in survival rates.
• As the anion gap increased past the threshold of 20 mEq/L, probability of survival was observed to drop.
• Specifically, when the anion gap was less than 20 mEq/L, the survival rate was 81%; at an anion gap of 20 to 24.9 mEq/L, the survival rate fell steeply to 47%, and for anion gaps of 25 mEq/L or higher, there were no observed survivals (0% survival rate).

Conclusion

• While the anion gap lacks diagnostic utility for pinpointing the exact cause of abdominal pain, it proves valuable as a prognostic tool.
• Hence, the study concludes that the anion gap could be a meaningful gauge in predicting survival outcome for horses experiencing abdominal pain, especially when the calculated anion gap goes beyond 20 mEq/L.