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Great question. Laying a patient flat (supine) increases venous return and blood flow to the brain, which further raises intracranial pressure (ICP). For a patient who already has high ICP, our priority is to help blood and cerebrospinal fluid drain away from the brain, not pool in it. Elevating the head of the bed to about 30° keeps the neck neutral and promotes venous outflow, which helps lower ICP. That’s why lying flat is contraindicated and elevating the head of the bed is the priority intervention.

No worries — this confuses a lot of people. Think of the skull as a rigid box that can only hold a fixed volume of brain tissue, blood, and CSF. When ICP is high, that box is already “full,” so anything that increases blood volume in the brain (like lying flat or straining) makes pressure climb even more and can reduce brain perfusion. By raising the head of the bed and keeping the neck midline, we’re using gravity to drain venous blood out of the skull, which frees up space and helps pressure come down. So the core idea is: with high ICP, we avoid anything that increases blood/pressure in the head and prioritize positioning that helps blood drain away.