Interpret this abg
Reading File
Finding Sources
Here is a full interpretation of this ABG:
ABG Interpretation — Ms. Lalitha (4/16/2026, 08:35 PM)
Raw Values
| Parameter | Value | Reference | Status |
|---|---|---|---|
| pH | 7.287 | 7.350–7.450 | ↓ Low |
| pCO₂ | 53.9 mmHg | 32.0–48.0 | ↑ High |
| pO₂ | 23.0 mmHg | 83.0–110 | ↓ Critically low |
| HCO₃⁻ (calc) | 25.0 mmol/L | 22–26 | Normal |
| SpO₂ | 32.5% | 95.0–99.0 | ↓ Critically low |
| Lactate | 2.7 mmol/L | 0.6–1.6 | ↑ High |
Step-by-Step Interpretation
1. Acidemia or Alkalemia?
pH = 7.287 → Acidemia
2. Primary Disorder?
- pCO₂ = 53.9 (↑) → consistent with respiratory acidosis
- HCO₃⁻ = 25.0 (normal) → no primary metabolic component
→ Primary Respiratory Acidosis
3. Is there Compensation?
Expected HCO₃⁻ for acute respiratory acidosis:
- For every 10 mmHg rise in pCO₂, HCO₃⁻ rises ~1 mEq/L (acute) or ~3.5 mEq/L (chronic)
- pCO₂ rose ~6 mmHg above upper limit (53.9 − 48 = ~6)
- Expected HCO₃⁻ rise: ~0.6 (acute) to ~2.1 (chronic)
- Measured HCO₃⁻ = 25.0 → borderline consistent with acute-on-chronic or acute respiratory acidosis with minimal compensation
4. Anion Gap?
AG = Na⁺ − (Cl⁻ + HCO₃⁻) = 131 − (112 + 25) = −6.2 mmol/L (reported as −6.2)
This is a negative/very low anion gap — likely due to hypoalbuminemia or laboratory artifact. With corrected albumin, the true AG may be higher.
Oxygenation Assessment
| Parameter | Value | Significance |
|---|---|---|
| pO₂ | 23.0 mmHg | Severe hypoxemia |
| SaO₂ | 32.5% | Critically desaturated |
| FO₂Hb | 31.9% | Only 31.9% of Hb carrying O₂ |
| FHHb | 66.1% | 66% deoxyhaemoglobin |
| A-a gradient | 60.5 mmHg | Markedly elevated (normal <15 mmHg) |
| a/A ratio | 27.6% | Severely impaired gas exchange |
The pO₂ of 23 mmHg with SaO₂ of 32.5% is critically life-threatening. The A-a gradient of 60.5 mmHg confirms significant ventilation-perfusion mismatch or shunt as the cause of hypoxemia — not hypoventilation alone.
Electrolyte Abnormalities
| Electrolyte | Value | Status |
|---|---|---|
| Na⁺ | 131 mmol/L | Hyponatraemia |
| K⁺ | 2.8 mmol/L | Hypokalaemia |
| Ca²⁺ | 1.00 mmol/L | Hypocalcaemia |
| Cl⁻ | 112 mmol/L | Mildly elevated |
Multiple electrolyte derangements are present — hyponatraemia, hypokalaemia, and hypocalcaemia together may worsen respiratory muscle function and cardiac arrhythmia risk.
Lactate
Lactate = 2.7 mmol/L (elevated). This suggests tissue hypoperfusion or hypoxia — consistent with the severe hypoxaemia seen, or early sepsis/circulatory compromise.
Summary Diagnosis
Acute (or acute-on-chronic) respiratory acidosis with severe hypoxaemic respiratory failure, elevated A-a gradient, mild lactic acidaemia, hyponatraemia, hypokalaemia, and hypocalcaemia.
Clinical Urgency
This is a critical ABG. Key concerns:
- pO₂ = 23 mmHg / SpO₂ = 32.5% — requires immediate escalation of oxygen therapy (high-flow O₂, NIV, or intubation depending on clinical context)
- Respiratory acidosis with CO₂ retention — suggests the patient is not ventilating adequately; evaluate for fatigue, obtundation, or impending respiratory arrest
- Elevated lactate — tissue hypoxia; assess perfusion and haemodynamics
- Electrolyte correction — especially K⁺ and Ca²⁺ given arrhythmia risk
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