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1. Check if the pH is abnormal (pH < 7.35 or > 7.45) to confirm an acid-base disorder exists.
2. Determine if the primary disturbance is respiratory or metabolic by evaluating PaCO₂ and HCO₃⁻ relative to pH.
3. If pH is low and PaCO₂ is high, it suggests respiratory acidosis; if pH is low and HCO₃⁻ is low, it suggests metabolic acidosis.
4. If pH is high and PaCO₂ is low, it suggests respiratory alkalosis; if pH is high and HCO₃⁻ is high, it suggests metabolic alkalosis.
5. Assess for compensation: check if the compensatory response (e.g., renal compensation in respiratory disorders or respiratory compensation in metabolic disorders) is appropriate for the time course.
6. In metabolic acidosis, calculate the anion gap to differentiate between high anion gap and normal anion gap acidosis.
7. If anion gap is elevated, consider causes like ketoacidosis, lactic acidosis, renal failure, or toxic ingestions.
8. If anion gap is normal, consider causes like diarrhea, renal tubular acidosis, or early renal failure.
9. In metabolic alkalosis, assess urinary chloride to differentiate between chloride-responsive and chloride-resistant types.
10. Evaluate for mixed acid-base disorders if the compensation does not match expected values or if multiple abnormalities are present.
11. Consider clinical context and patient history to correlate laboratory findings with potential underlying pathologies.
12. Treat the underlying cause and correct severe acid-base imbalances as clinically indicated, using fluids, electrolytes, or ventilation adjustments as needed.