What Is Cerebral Perfusion Pressure?

Cerebral perfusion pressure (CPP) is the difference between the pressure found in the arteries, called the mean arterial pressure (MAP) and the pressure inside the cranium (inter-cranial pressure or ICP). It is determined by this equation: CPP = MAP -- ICP.

Significance

• The cerebral perfusion pressure is normally held at an even level to provide constant and steady blood flow to the brain by loosening or tightening the cerebral blood vessels. This means that the brain receives the proper amount of blood even if the blood pressure in the rest of the body spikes or drops.

Brain Injury

• When a brain injury occurs it can lead to a decrease in cerebral perfusion pressure. If it sinks low enough, the brain is at risk for ischemia -- a reduction in blood flow that causes brain damage.

Critical CPP

• Trauma.org reports that there is no definitive, optimal cerebral perfusion pressure, but that there is a critical threshold below which the CPP should not be allowed to fall. The critical threshold is thought to be around 60 milligrams of mercury (mm Hg), according to the Internet Journal of Anesthesiology.

CPP Maintenance

• Maintaining CPP following a head trauma is generally accomplished by controlling inter-cranial pressure and artificially raising blood pressure.

Mortality

• The mortality rate of patients rises approximately 20% for every 10 milligrams of mercury that the cerebral perfusion pressure drops below the critical threshold, according to http:www.trauma.org.