BT_RA 1.12 Determinants of ICP and their regulation Pt 2


This sculpture by Barry Flanagan will hopefully put you in a thinking mood…..

Today a little exercise to work through.

It will enable you to answer the question, “How can you manipulate blood pressure to minimise cerebral blood volume ( within the limits of cerebral autoregulation)?”

Before we start, what is you first thought?

Over 90% of registrars, to whom I have posed this question, come up with the incorrect answer.

When I start to probe their reasoning, most draw a graph which relates cerebral blood flow to MAP. It is a reasonable place to start.  Have a go at drawing that graph.

Now write an equation that shows the relationship between flow and pressure.

What is the third variable?

If flow remains constant in the face of changing pressure, what else is changing? Which direction does this change occur in order to maintain constant flow at both a high and low MAP?

Returning to your original graph, what is the relative calibre of the blood vessels at each end of the flat portion of the curve?

Have you changed your answer to the original question?

I’ll be back on the weekend with some more on this ….

UPDATE 20/5: you can find some more on this topic here

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