Decreased effective hemoglobin concentration which causes a decrease in the oxygen-carrying capacity of the blood, rarely accompanied by hypoxemia, is known as?

1. A

   Hypoxemic hypoxia

2. B

   Histotoxic hypoxia

3. C

   Circulatory hypoxia

4. D

   Anemic hypoxia

Appeared in: MNS 2024

Explanation

• Anemic hypoxia is defined by a reduction in the oxygen-carrying capacity of the blood due to decreased or dysfunctional hemoglobin.
• In this condition, the partial pressure of oxygen in the arterial blood (PaO2) remains normal, so it is not typically associated with hypoxemia.
• The root cause is either a low concentration of hemoglobin (as in anemia) or hemoglobin being unavailable for oxygen transport (as in carbon monoxide poisoning).
• Although blood oxygen saturation (SpO2) and PaO2 are normal, the total amount of oxygen delivered to the tissues is insufficient.

Why Other Options Were Wrong

• Option A: Hypoxemic hypoxia is incorrect because it is fundamentally defined by low arterial oxygen tension (PaO2), which means hypoxemia is a primary and defining feature, contradicting the question's description that hypoxemia is rare.
• Option B: Histotoxic hypoxia is incorrect because the problem lies within the cells' inability to utilize oxygen, not with the blood's capacity to carry it. In histotoxic hypoxia, oxygen delivery to the tissues is normal.
• Option C: Circulatory hypoxia is incorrect because it is caused by reduced blood flow (stagnation) to the tissues. The oxygen content and carrying capacity of the blood are normal, but the delivery rate is too slow.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Classification and pathophysiology of different types of hypoxia helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• A critical nursing implication is recognizing that a normal pulse oximetry reading (SpO2) does not rule out significant hypoxia. In anemic and histotoxic hypoxia, SpO2 can be normal because it only measures the saturation of available hemoglobin, not the total oxygen content or tissue utilization.
• Nurses must assess the whole clinical picture, including skin color, mental status, heart rate, and respiratory rate, to detect hypoxia, especially when conditions like anemia or potential poisoning are present.
• What if? If the patient had severe COPD and presented with confusion and shortness of breath, the most likely cause would be hypoxemic hypoxia due to ventilation-perfusion mismatch. In this case, the SpO2 would be low, and oxygen therapy would be a primary treatment.

How to Approach the Question

• First, carefully read the question and identify the key defining characteristics of the condition described. The key phrases are 'decreased effective hemoglobin concentration,' 'decrease in the oxygen-carrying capacity,' and 'rarely accompanied by hypoxemia.'
• Analyze the term 'hypoxemia,' which means low oxygen in the arterial blood (low PaO2). The question states this is rare, which is a major clue.
• Consider each option's definition. 'Anemic' directly relates to blood and hemoglobin. 'Hypoxemic' relates to low blood oxygen. 'Circulatory' relates to blood flow. 'Histotoxic' relates to tissue poisoning.
• Match the defining characteristics from the stem to the options. The problem is with hemoglobin (anemia) and oxygen-carrying capacity, while PaO2 is normal. This perfectly aligns with the definition of anemic hypoxia.
• Eliminate the other options based on the key differentiator. Hypoxemic hypoxia is ruled out by the absence of hypoxemia. Circulatory and histotoxic hypoxia are ruled out because the primary defect is not blood flow or tissue utilization.

Concept Tested & Keywords

• Concept Tested: Classification and pathophysiology of different types of hypoxia.
• Stem keywords: Decreased effective hemoglobin, oxygen-carrying capacity, hypoxemia
• Lead-in keywords: is known as
• Negative lead-in flag: false

Question ID

Q0ICGP_X_OlqrOXTjl6M-K

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 1 p. 318-320

E6 Physiology Guyton 4SAE Part 2A p. 94-96

E6 Physiology Essentials Sembulingam 10e Part 3 p. 3-5