Normal cerebral perfusion pressure is ____ mmHg.

• A. 40
• B. 50
• C. 60
• D. 70

Answer: (B)

Cerebral perfusion pressure (CPP) is the pressure that drives blood flow to the brain and is calculated as mean arterial pressure minus intracranial pressure. The brain can keep blood flow fairly stable over a wide range of CPP through autoregulation, but this stability has a lower limit. When CPP drops to that lower boundary, autoregulation can no longer maintain adequate flow, and cerebral perfusion becomes compromised, increasing the risk of ischemia. That lower limit is the value this item is targeting as the normal CPP. In practice, clinicians aim to stay above this threshold to ensure adequate brain perfusion, and they often target a somewhat higher level depending on the clinical situation. Values below the threshold would risk ischemia, while values well above it still maintain perfusion and are generally acceptable, though extremely high CPP can have other risks in certain conditions.