>I would imagine the main reason for their higher blood pressure is so blood is able to reach their heads, you need roughly 23mmHg per foot in height.

It's a closed loop system, so as long as it's primed you don't need much pressure to pump it from an engineering point of view, as long as you replace the blood vessels with non-compliant tubes.

Just throw a 12v centrifugal pump on there and you should be OK.