Blood Gases Flow Chart: MR RM
Description
Mister Ronald McDonald (MR RM) is a helpful flowchart for interpreting acid-base disorders, specifically for determining whether a patient’s condition is due to a metabolic (M) or respiratory (R) cause:
1. Check the pH (7.4 is the cutoff)
• pH > 7.4 → Alkalosis
• pH < 7.4 → Acidosis
2. Assess Carbon Dioxide (CO₂) Levels (PaCO₂)
• The key threshold is 40 mmHg:
• If CO₂ > 40 mmHg, this suggests respiratory acidosis or metabolic alkalosis.
• If CO₂ < 40 mmHg, this suggests respiratory alkalosis or metabolic acidosis.
3. Determine the Cause
• In Alkalosis:
• If CO₂ > 40, the cause is Metabolic (M) Alkalosis.
• If CO₂ < 40, the cause is Respiratory (R) Alkalosis.
• In Acidosis:
• If CO₂ > 40, the cause is Respiratory (R) Acidosis.
• If CO₂ < 40, the cause is Metabolic (M) Acidosis.
Key Takeaway
• The chart helps determine whether a patient’s acid-base imbalance is due to a metabolic or respiratory cause by analyzing pH and CO₂ levels.
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