Neuro ICU > Cerebral Perfusion Pressure
Cerebral Perfusion Pressure (CPP)
What is CPP?
CPP is the net pressure gradient driving oxygen delivery to the brain. It is the difference between MAP and ICP.
Calculated with the formula: CPP = MAP - ICP
Normal range is 60-80 mm Hg. CPP should be kept at more than 60 mmHg for best outcomes. This is typically associated with TBI, but can occasionally be measured after a CVA, especially hemorrhagic.
| Decision | CPP Range | Clinical Action |
|---|---|---|
| GO | 60–65 mmHg | Proceed with activity. Optimal range for cerebral perfusion. |
| MODIFY | 50–59 mmHg or 65–70 mmHg | Light, in-bed activity only. HOB ≥30°. Discuss with RN and/or team before proceeding. |
| DEFER | <50 mmHg or >70 mmHg | Do not initiate activity. Notify RN. CPP <30 mmHg indicates poor prognosis and irreversible neuronal hypoxia. |
Why Do We Care?
Low CPP can result in further ischemic damage. CPP of < 50 mmHg is associated with poor outcomes in TBI and < 30 indicates a poor prognosis, resulting in irreversible neuronal hypoxia.
Cerebral Autoregulation
Under normal conditions, the brain autoregulates cerebral blood flow across a wide range of MAPs (approximately 50–150 mmHg), keeping perfusion constant despite changes in systemic blood pressure. In a healthy brain, CPP is therefore relatively stable.
After significant brain injury — TBI, hemorrhagic stroke, large ischemic stroke — this autoregulatory capacity is often impaired or lost. The injured brain becomes pressure-passive: CPP rises and falls with MAP, making adequate perfusion pressure a critical target and explaining why neuro patients often have individualized BP parameters.
This is why activity that causes large hemodynamic fluctuations in a neuro patient requires careful monitoring — and why communication with the team about the patient's autoregulatory status matters.
References
Esbrook, C., Laxton, L., & Morrow, M. (2024). Critical care and early rehabilitation. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (3rd ed., pp. 115–137). AOTA Press.
Hamby, J. (2017). The Nervous System. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (2nd ed.). AOTA Press.
Mount, C. A., & Das, J. M. (2021). Cerebral Perfusion Pressure. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK537271/
Clark, K. (2017). Intensive Care Unit. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (2nd ed., pp. 115–135). AOTA Press. https://library.aota.org/OT_in_Acute_Care_2e/134?highlightText=intensive%20care%20unit