A patient with anemia and Pa 02 is decreased: Anemic hypoxia Hypoxic hypoxia Secondary polycythemia
Reading File
Finding Sources
Reading File
Reading File
The answer is clearly framed by the two clinical parameters given: anemia (low hemoglobin) AND decreased PaO2.
Answer: Both Anemic Hypoxia AND Hypoxic Hypoxia - but the question asks you to identify which type EACH parameter points to.
The correct answer to this type of MCQ is Hypoxic Hypoxia - here is the full reasoning:
The Four Types of Hypoxia - Key Differentiator: PaO2
| Type | PaO2 | Cause |
|---|---|---|
| Hypoxic hypoxia (Hypoxemia) | Decreased | Low inspired O2, lung disease, hypoventilation, shunts |
| Anemic hypoxia | Normal | Low Hb, CO poisoning - O2 carrying capacity reduced |
| Stagnant/Ischemic hypoxia | Normal | Low blood flow - reduced O2 delivery |
| Histotoxic hypoxia | Normal | Cells can't use O2 (e.g., cyanide poisoning) |
Breaking Down This Patient
Finding 1: Anemia → This alone would cause anemic hypoxia - reduced O2-carrying capacity, but PaO2 is typically normal in pure anemia.
Finding 2: Decreased PaO2 → This is the critical clue. Per Ganong's Review of Medical Physiology and Harrison's Principles of Internal Medicine:
"Hypoxic hypoxia (hypoxemia) = PO2 of arterial blood is reduced"
"Anemic hypoxia = arterial PO2 is normal but hemoglobin available to carry O2 is reduced"
Since the PaO2 is decreased in this patient, this rules out pure anemic hypoxia (which has normal PaO2) and points to Hypoxic hypoxia.
The Trick in This Question
The question presents anemia + decreased PaO2 as a combined scenario. The decreased PaO2 is the defining feature:
- Anemic hypoxia = anemia present, but PaO2 is normal - does NOT fit (PaO2 is decreased here)
- Hypoxic hypoxia = PaO2 is decreased - this fits the lab finding perfectly
The correct answer is Hypoxic Hypoxia (also called hypoxemic hypoxia).
What About Secondary Polycythemia?
Secondary polycythemia is a compensatory response to chronic hypoxia (via increased erythropoietin production triggered by HIFs in low-O2 conditions). It is NOT a type of hypoxia - it is a consequence of prolonged hypoxia, particularly hypoxic hypoxia. So it does not apply here as a classification of the patient's hypoxia type.
Summary
| Option | Applies? | Why |
|---|---|---|
| Anemic hypoxia | No (not the best fit) | PaO2 is normal in anemic hypoxia; here PaO2 is decreased |
| Hypoxic hypoxia | Yes | Defined by decreased PaO2 - matches the clinical data |
| Secondary polycythemia | No | This is a compensatory response, not a type of hypoxia |
The answer is Hypoxic Hypoxia - because the PaO2 is decreased, which is the hallmark feature distinguishing it from anemic hypoxia (where PaO2 remains normal despite reduced O2-carrying capacity).
- Ganong's Review of Medical Physiology, 26th Ed., p. 648
- Harrison's Principles of Internal Medicine 22E, Causes of Hypoxia section
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