Critical care: oxygen delivery: practice question

A Anaesthesia question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anaesthesia · Critical care: oxygen delivery

Sample item

Which change produces the largest increase in oxygen delivery in a severely anaemic patient with normal saturation and cardiac output?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Raising the haemoglobin concentration

Oxygen delivery equals cardiac output times arterial oxygen content, and content is mainly haemoglobin times 1.34 times saturation. Dissolved oxygen contributes very little at normal pressures. Raising haemoglobin therefore has the greatest effect when anaemia is the limiting factor.

Option by option

  • A. Doubling the dissolved oxygen by increasing PaO2

    Dissolved oxygen is a minor contributor.

  • B. Giving a vasodilator

    A vasodilator does not increase oxygen content.

  • C. Raising the haemoglobin concentration (correct)

    Correct. Haemoglobin is the major determinant of oxygen content.

  • D. Reducing the heart rate

    Reducing the heart rate would tend to lower cardiac output.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is C, Raising the haemoglobin concentration. Oxygen delivery equals cardiac output times arterial oxygen content, and content is mainly haemoglobin times 1.

Why is "Doubling the dissolved oxygen by increasing PaO2" not the answer?

Dissolved oxygen is a minor contributor.

Why is "Giving a vasodilator" not the answer?

A vasodilator does not increase oxygen content.

Why is "Reducing the heart rate" not the answer?

Reducing the heart rate would tend to lower cardiac output.

What concept does this question test?

It tests Critical care: oxygen delivery in Anaesthesia. 34 times saturation. Dissolved oxygen contributes very little at normal pressures. Raising haemoglobin therefore has the greatest effect when anaemia is the limiting factor.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Critical care: oxygen delivery?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.