Cardiovascular system: transcapillary refill after haemorrhage: practice question

A Physiology 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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Physiology · Cardiovascular system: transcapillary refill after haemorrhage

Sample item

A man loses 1 litre of blood from a road accident and bleeding is then controlled. Over the next 24 hours his haemoglobin concentration falls further without any more bleeding or transfusion. Which mechanism is mainly responsible?

AMarrow suppression that stops red cell production within hoursBSuppressed ADH causing a water diuresisCIntravascular haemolysis of the remaining red cellsDFall in capillary hydrostatic pressure, drawing interstitial fluid into the plasma

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

The answer and the reasoning

D. Fall in capillary hydrostatic pressure, drawing interstitial fluid into the plasma

Haemorrhage lowers arteriolar and capillary pressure, so reabsorption exceeds filtration and interstitial fluid moves into the vascular space (transcapillary refill). This restores plasma volume over hours but dilutes the remaining red cells, so haemoglobin concentration falls further.

Option by option

A. Marrow suppression that stops red cell production within hours
Marrow output does not stop within hours, and a lack of new cells would not lower concentration so quickly.
B. Suppressed ADH causing a water diuresis
After haemorrhage ADH is raised, not suppressed, and a water diuresis would concentrate the blood.
C. Intravascular haemolysis of the remaining red cells
Haemolysis is not a feature of simple blood loss.
D. Fall in capillary hydrostatic pressure, drawing interstitial fluid into the plasma (correct)
Correct. Low capillary hydrostatic pressure shifts fluid into plasma and dilutes red cells.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Fall in capillary hydrostatic pressure, drawing interstitial fluid into the plasma. Haemorrhage lowers arteriolar and capillary pressure, so reabsorption exceeds filtration and interstitial fluid moves into the vascular space (transcapillary refill).

Why is "Marrow suppression that stops red cell production within hours" not the answer?

Marrow output does not stop within hours, and a lack of new cells would not lower concentration so quickly.

Why is "Suppressed ADH causing a water diuresis" not the answer?

After haemorrhage ADH is raised, not suppressed, and a water diuresis would concentrate the blood.

Why is "Intravascular haemolysis of the remaining red cells" not the answer?

Haemolysis is not a feature of simple blood loss.

What concept does this question test?

It tests Cardiovascular system: transcapillary refill after haemorrhage in Physiology. This restores plasma volume over hours but dilutes the remaining red cells, so haemoglobin concentration falls further.

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 Cardiovascular system: transcapillary refill after haemorrhage?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.