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Cerebral perfusion pressure (CPP) is the pressure in the arteries leading to the brain, the blood pressure in the jugular veins, and the intracranial pressure (ICP) inside the head. It must remain in a narrow range for healthy blood flow and neurological activity. Monitoring CPP is important for head injury victims.
The brain is a complex organ that requires an adequate blood supply to function normally. Blood flow to the brain is called perfusion. Cerebral perfusion pressure (CCP) is typically the strength of the pressure in the arteries leading to the brain, the blood pressure in the jugular veins, and the intracranial pressure (ICP) inside the head. Mean arterial pressure can push blood into the head, while ICP lowers CCP. Blood vessels in the brain called arterioles are usually able to widen to lower blood pressure, but can narrow to raise it.
Through self-regulation, the arteries in the brain can widen and narrow to keep the pressure in the brain relatively constant. Changing the blood pressure in the body, therefore, typically doesn’t have much effect. If the cerebral perfusion pressure is not regulated in the normal way, this can result in passive flow to the pressure. There can be inadequate blood pressure in the brain, resulting in oxygen starved cells causing a condition called ischemia.
Too much pressure in the brain can trigger neurological damage and can cause parts of the organ to herniate. Cerebral perfusion pressure typically must remain in a narrow range for blood flow and neurological activity to be healthy. It is often compromised after a head injury, and clinicians can monitor CPP by monitoring jugular venous pressure and oxygen saturation. If blood flow to the brain is too low, this saturation value will drop because more oxygen is being drawn from what little blood supply is available.
Cerebral perfusion pressure can also be monitored by assessing the metabolic activity of brain cells. Positron emission tomography (PET) scans are often used to visualize these areas and compare this activity to CPP. Sometimes a catheter is inserted into the brain to assess the metabolic state of an area. This method is typically invasive and the presence of the catheter can change the physical state of the areas to be measured.
Sometimes a patient’s symptoms can be used to determine cerebral perfusion pressure. Doctors can estimate ICP based on whether someone is experiencing confusion or sleepiness, for example. The mean arterial pressure can be used with the resulting numerical estimate to determine CPP. Outcomes for head injury victims are often predicted by also monitoring cerebral perfusion pressure, as blood flow and pressures in the head usually correlate with brain function and its ability to heal.
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