ABG

A 5 step approach to arterial blood gas interpretation is advocated.

1. How is the patient?

• 2. Is the patient hypoxaemic?
• - The Pa02 on air should be 10.0-13.0 kPa

3. Is the patient acidaemic (pH <7.35) or alkalaemic (pH >7.45)?

• 4. What has happened to the PaCO2?
• - If there is acidaemia, an elevated PaCO2 will account for this

• 5. What is the bicarbonate level or base excess?
• - A metabolic acidosis will have a low bicarbonate level and a low base excess (< -2 mmol)
• - A metabolic alkalosis will have a high bicarbonate and a high base excess (> +2 mmol)

If there is acidaemia, an elevated PaCO2 will account for this

• - A metabolic acidosis will have a low bicarbonate level and a low base excess (< -2 mmol)
• - A metabolic alkalosis will have a high bicarbonate and a high base excess (> +2 mmol)