Pearls

Interpretation of Blood Gas Results

• Evaluate the pH. If it is abnormal, an acid-base disturbance is present.
• If the pH is within the RI but the pCO₂ and HCO₃^– are abnormal, a mixed acid-base disturbance is probably present.
• If the pH is low and the pCO₂ is high, respiratory acidosis is present.
• If the pH is high and the pCO₂ is low, respiratory alkalosis is present
• If the pH is low and the HCO₃^– is low, metabolic acidosis is present.
• If the pH is high and the HCO₃^– is high, metabolic alkalosis is present.
• Check for appropriate compensation for the abnormality.
• Respiratory acidosis should be compensated for by increasing HCO₃^–.
• Respiratory alkalosis should be compensated for by decreasing HCO₃^–.
• Metabolic acidosis should be compensated for by decreasing pCO₂.
• Metabolic alkalosis should be compensated for by increasing pCO₂.
• If the compensation is appropriate, the acid-base disturbance is simple. If there is inappropriate compensation, the acid-base disturbance may be mixed.
• Determine if the type of disturbance is compatible with the patient’s history and clinical findings.

Interpretation of Bicarbonate, Anion Gap, and Chloride on Biochemical Panels

• If the HCO₃^– is low and the anion gap is high, there is a metabolic acidosis associated with acid accumulation (e.g. lactic acid, ketoacids, renal acids, ethylene glycol).
• If the HCO₃^– is low and the anion gap is normal, there is a metabolic acidosis likely due to bicarbonate loss (renal or intestinal).
• If the HCO₃^– is high and chloride is disproportionately low compared to sodium, there is a metabolic alkalosis. In small animals, an intestinal obstruction or upper GI pathology must be considered, whereas in ruminants an abomasal disorder is most likely.
• If the HCO₃^– is normal and the anion gap is high, a mixed acid-base disturbance is likely.
• Determine if the type of disturbance is compatible with the patient’s history and clinical findings.
• Blood gas analysis may be useful when a mixed acid-base disturbance is suspected or when the primary problem is suspected to be respiratory in origin.