Arterial Blood Gas, Electrolyte and Acid-Base Values as Diagnostic and Prognostic Indicators in Equine Colic

SIMPLE SUMMARY: Gastrointestinal pain (colic) is one of the most frequent emergencies seen in equine practice and can be caused by several different processes, making diagnosis challenging. Deciding between medical and surgical treatment is very important and, when needed, early surgical intervention can improve survival. However, colic surgery is an invasive and expensive treatment. Results from physical examination and clinical parameters are used to identify surgical cases and establish the prognosis. No individual parameter or group of parameters has been shown to be sensitive or specific for this. This study investigated if arterial blood gas, electrolyte and acid-base analysis in conscious horses presenting with signs of colic and breathing ambient air differed from previously reported values in healthy horses and had diagnostic or prognostic value. We found significant differences between previously described data from healthy horses and the study cohort of colic cases, between some different types of colic, between surgical and non-surgical cases and between surviving and non-surviving animals. From these data, we identified specific components which demonstrated diagnostic and prognostic value. ABSTRACT: The study aimed to investigate if arterial blood analysis in conscious horses presenting with signs of colic and breathing ambient air had diagnostic or prognostic value. Arterial blood samples from 352 horses presenting with colic at a university equine referral hospital were analysed for pH, partial pressure of carbon dioxide (PaCO(2)), partial pressure of oxygen (PaO(2)), concentrations of sodium (Na(+)), potassium (K(+)), ionised calcium (Ca(2+)) and chloride (Cl(−)), actual and standardised plasma bicarbonate concentration (HCO(3)(−) (P) and HCO(3)(−) (P, st)), blood and extracellular fluid base excess (Base (B) and Base (ecf)) and anion gap (AG). Results were compared to previously reported values for healthy horses, and comparisons were made between final diagnosis, treatment and survival to hospital discharge. Significant differences were found between colic cases and healthy reference values between some primary aetiologies. Overall, surgical and non-surgical colic cases differed in Ca(2+) and Cl(−) concentrations and Ca(2+) differed between cases that survived to discharge and those that did not. PaO(2) differed between small intestinal surgical cases that survived and those that did not. From these results, we developed regression models that demonstrated excellent or good predictive value in identifying the likelihood of surgical versus medical management and survival to hospital discharge.