70yo male with exacerbation of CAL on IPPV.

What is the acid-base disorder?

Mixed Metabolic & Respiratory Alkalosis

• pH : alkalosis
• PCO₂ : respiratory alkalosis
• if only disorder, HCO₃^- should be ≈ 26-28 mmol/L
• HCO₃^- : metabolic alkalosis
• if only disorder, PCO₂ should be ≈ 47 mmHg
• PO₂ + 1.25*PCO₂ ≈ 115 : need FIO₂ but likely marked rise AaDO₂

ABG Correction Factors

1. Metabolic Acidosis:
• PCO₂ : last 2 digits of pH ≥ 7.10
• HCO₃^- : for each 10 mmol/L fall → ↓ PCO₂ ≈ 12 mmHg
2. Metabolic Alkalosis:
• PCO₂ : last 2 digits of pH ≤ 7.60
• HCO₃^- : for each 10 mmol/L rise → ↑ PCO₂ ≈ 7 mmHg
• *least well compensated due to hypoxaemia 2° hypoventilation
3. Respiratory Acidosis:
• Acute : for each 10 mmHg PCO₂ rise → ↑ HCO₃^- ≈ 1-2 mmol/L
• Chronic : for each 10 mmHg PCO₂ rise → ↑ HCO₃^- ≈ 4 mmol/L
4. Respiratory Alkalosis:
• PCO₂ : for each 10 mmHg fall → ↓ HCO₃^- ≈ 2.5 mmol/L