NBME 20 Hypoventilation to increase cerebral blood flow

"A 45-year old man is undergoing a surgical..." The Q asks how to increase intracranial pressure and the correct answer is "decreasing respiratory rate".

I had thought hypoventilation led to vasodilation --> then vasodilation led to "pooling" of blood that then led to increased intracranial pressure.

But, apparently vasodilation causes increased "blood flow", and somehow this is the reason for increased intracranial pressure... However, I thought from a physics perspective if you constrict, i.e. make a vessel smaller in diameter, it increases velocity which increases blood flow..

So, I have 2 questions.. 1. How do you think about this properly? 2. And, why during a surgery would an anesthesiologist want to increase intracranial pressure?