π§ Cerebral Perfusion Pressure Calculator
CPP = MAP minus ICP. Target 60 to 70 mmHg.
Educational only. Neurocritical care decisions belong to the ICU team.
The brain needs blood pushed through it, and cerebral perfusion pressure is the number that says whether that is happening. CPP is simply mean arterial pressure minus intracranial pressure: the driving pressure into the skull minus the pressure resisting it inside. Guidelines target 60 to 70 mmHg. This calculator derives MAP from systolic and diastolic, subtracts ICP, and places the result against the target.
How to Use This Calculator
Enter systolic and diastolic blood pressure and the ICP reading. The MAP and CPP compute instantly.
Enter systolic and diastolic pressure in mmHg from the arterial line or cuff.
Enter ICP in mmHg from the external ventricular drain or monitor.
Read CPP against the 60-70 target. Below 60 needs attention; below 50 is critical.
The Formula and the Target
MAP weights diastole double because the cardiac cycle spends twice as long in diastole; the one-third pulse-pressure formula is the standard bedside estimate. Subtracting ICP gives the net pressure perfusing the brain: blood can only enter the rigid skull if arterial pressure exceeds the pressure inside it. The 60-70 target comes from the Brain Trauma Foundation guidelines for severe TBI, balancing ischemia below against the harms of pushing pressure too high (ARDS risk, excessive fluids and vasopressors).
Cerebral autoregulation complicates the picture: healthy brains hold blood flow constant across a wide CPP range by adjusting vessel caliber, but injured brains often lose this ability, making flow pressure-passive. That is why CPP is monitored in the first place: when autoregulation fails, the number on this page is nearly the whole story of brain perfusion. Advanced centers individualize targets with autoregulation monitoring (PRx), but 60-70 remains the default.
Worked Example
Blood pressure 110/70, ICP 25. MAP = 70 + (110-70)/3 = 83.3 mmHg. CPP = 83.3 - 25 = 58.3 mmHg: just below target. The clinician's levers: lower ICP (CSF drainage, osmotherapy, sedation, head elevation) or raise MAP (vasopressors, fluids), choosing based on which side is more abnormal. Here the ICP of 25 is the problem (target under 20-22), so ICP-directed therapy comes first. Contrast 90/60 with ICP 10: MAP = 70, CPP = 60, in target despite lowish blood pressure, because the ICP is fine. The two pressures trade off; the difference is what counts.
Raising CPP: Which Lever to Pull
Low CPP has two parents, and treatment picks the guilty one. High ICP gets osmotherapy (hypertonic saline, mannitol), CSF drainage via ventriculostomy, optimized sedation and analgesia, head-of-bed elevation to 30 degrees, and avoidance of hypercapnia, fever, and seizures, all of which raise ICP. Low MAP gets fluids if volume-responsive, then vasopressors, typically norepinephrine. Pushing MAP above 90-100 to chase CPP has diminishing returns and real harms, which is why the target has a ceiling, not just a floor.
Herniation is the catastrophe the whole framework exists to prevent: when ICP approaches MAP, CPP approaches zero and the brainstem compresses. Warning signs include blown pupils, posturing, and the Cushing triad (hypertension, bradycardia, irregular respirations). This page computes the number; recognizing the patient in front of you is the ICU team's job, and this content is education for understanding their decisions, not for making them.
Beyond the Number: Multimodal Monitoring
Modern neurocritical care reads CPP alongside brain tissue oxygen (PbtO2), microdialysis, and autoregulation indices, because adequate pressure does not guarantee adequate oxygenation. A CPP of 65 with a PbtO2 of 12 is still brain hypoxia and gets treated. Conversely, chasing higher CPP with aggressive vasopressors can worsen lung injury without helping the brain. The number on this page is one instrument on a panel, and the art is reading them together. For students: learn the formula cold, then learn its limits; both are tested, but only the second saves patients.
Related Calculators
Keep exploring: try our cardiac index and cardiac output for the next piece of the picture.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is cerebral perfusion pressure?
The net pressure driving blood through the brain: CPP = MAP - ICP (mean arterial pressure minus intracranial pressure), in mmHg. Guidelines target 60-70 mmHg in severe traumatic brain injury.
How do you calculate CPP?
First compute MAP = diastolic + (systolic - diastolic)/3, then subtract ICP. Example: BP 110/70 gives MAP 83.3; with ICP 25, CPP = 58.3 mmHg. This calculator does both steps.
What is a normal CPP?
The Brain Trauma Foundation target for severe TBI is 60-70 mmHg. Below 60 risks brain ischemia; below 50 is critical. Above 70 offers little added benefit and the therapies to get there carry harms.
What raises intracranial pressure?
Bleeding, swelling, or masses inside the rigid skull; also hypercapnia, fever, seizures, pain, suctioning, flat head position, and venous obstruction. Treatment targets the cause: drainage, osmotherapy, sedation, positioning.
How do you increase cerebral perfusion pressure?
Lower ICP (CSF drainage, hypertonic saline/mannitol, sedation, head elevation) or raise MAP (fluids, vasopressors like norepinephrine). The choice depends on which side is abnormal. Avoid pushing MAP excessively.
What happens when CPP is too low?
Brain ischemia: inadequate blood flow starves neurons of oxygen. Sustained low CPP causes secondary brain injury after trauma. At the extreme, ICP approaching MAP means herniation risk, a neurosurgical emergency.
What is cerebral autoregulation?
The brain's ability to hold blood flow constant across a range of perfusion pressures by adjusting vessel diameter. Brain injury often impairs it, making flow pressure-passive, which is exactly when CPP monitoring matters most.
Why is MAP calculated as diastolic plus one-third pulse pressure?
Because the cardiac cycle spends roughly twice as long in diastole as systole, so the time-averaged pressure weights diastole double. It is the standard bedside estimate; arterial line monitors compute the true average.
What is the Cushing triad?
Hypertension (widening pulse pressure), bradycardia, and irregular respirations: the classic late sign of dangerously raised ICP and impending herniation. It demands immediate neurosurgical evaluation.
Does high CPP cause harm?
Pushing CPP above target with aggressive fluids and vasopressors is linked to ARDS and other harms without clear brain benefit, which is why guidelines cap the target at 70. More pressure is not always better.