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Cerebral perfusion pressureCerebral perfusion pressure, or CPP, is the net pressure causing blood flow to the brain. It must be maintained within narrow limits because too little pressure could cause brain tissue to become ischemic (having inadequate blood flow), and too much could raise intracranial pressure (ICP). Additional recommended knowledgeCPP can be defined as the pressure gradient causing cerebral blood flow (CBF) such that
where:
The three pressures that can contribute to the CPP are:
In many tissues, the perfusion pressure is just the pressure difference between the arterial side (the upstream pressure) and the venous side (downstream pressure). In some tissues there is a third pressure to consider and this is the pressure external to the blood vessels because if high this pressure can restrict flow through the tissue. This situation is known as a Starling resistor. Such a situation existys in the brain where the external pressure is the ICP. Consequently, the correct definition of CPP is:
or
Raising MAP raises CPP and raising ICP lowers it (this is one reason that increasing ICP in traumatic brain injury is potentially deadly). CPP, or MAP minus ICP, is normally between 70 and 90 mmHg in an adult human, and cannot go below 70 mmHg for a sustained period without causing ischemic brain damage.[1] Children require pressures of at least 60 mmHg.[1]
References
Categories: Neurology | Neurotrauma | Physiology |
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cerebral_perfusion_pressure". A list of authors is available in Wikipedia. |