Paediatric anaesthesia: allowable blood loss: 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.

Try it

Anaesthesia · Paediatric anaesthesia: allowable blood loss

Sample item

A 20 kg child has an estimated blood volume of 75 mL/kg and a haematocrit of 36%. The lowest acceptable haematocrit is 24%. What is the maximum allowable blood loss, using the average haematocrit?

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

The answer and the reasoning

D. 600 mL

The estimated blood volume is 20 times 75, which is 1500 mL. The maximum allowable blood loss equals blood volume multiplied by the haematocrit fall divided by the average haematocrit, which is 1500 times 12 divided by 30 and gives 600 mL. Using the starting haematocrit alone would underestimate the permissible loss.

Option by option

  • A. 750 mL

    This divides by the lower haematocrit of 24 and overestimates the loss.

  • B. 300 mL

    This halves the correct figure and has no basis in the formula.

  • C. 500 mL

    This divides by the starting haematocrit of 36 and underestimates the loss.

  • D. 600 mL (correct)

    Correct. 1500 times 12 divided by the mean of 36 and 24 equals 600 mL.

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.

More Anaesthesia questions

Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, 600 mL. The estimated blood volume is 20 times 75, which is 1500 mL.

Why is "750 mL" not the answer?

This divides by the lower haematocrit of 24 and overestimates the loss.

Why is "300 mL" not the answer?

This halves the correct figure and has no basis in the formula.

Why is "500 mL" not the answer?

This divides by the starting haematocrit of 36 and underestimates the loss.

What concept does this question test?

It tests Paediatric anaesthesia: allowable blood loss in Anaesthesia. The maximum allowable blood loss equals blood volume multiplied by the haematocrit fall divided by the average haematocrit, which is 1500 times 12 divided by 30 and gives 600 mL. Using the starting haematocrit alone would underestimate the permissible loss.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Paediatric anaesthesia: allowable blood loss?

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.