Cerebral Perfusion Pressure Target in Brain Injury
The recommended cerebral perfusion pressure (CPP) target for patients with brain injury is ≥60 mmHg, which should be adjusted (individualized) based on neuromonitoring data and the cerebral autoregulation status of the individual patient. 1
Understanding CPP Targets
- CPP is calculated as the difference between mean arterial pressure (MAP) and intracranial pressure (ICP): CPP = MAP - ICP 2
- The reference point for measuring MAP should be placed at the external ear tragus to ensure accurate CPP calculations 2, 3
- For most patients with severe traumatic brain injury, maintaining CPP between 60-70 mmHg is recommended 2, 3
Evidence-Based CPP Management
- When ICP monitoring becomes available, maintaining CPP ≥60 mmHg is the current standard recommendation with 95% expert agreement 1
- CPP values >70 mmHg are not routinely recommended as they have been associated with a 5 times higher incidence of respiratory distress syndrome without improving neurological outcomes 2, 4
- CPP exceeding 90 mmHg may worsen vasogenic cerebral edema, highlighting the importance of avoiding excessively high CPP values 2, 3
Special Considerations for CPP Management
- For patients with combined hemorrhagic shock and severe traumatic brain injury, the target MAP should be ≥80 mmHg to maintain adequate CPP 3
- In cases of cerebral herniation or threatened intracranial hypertension, osmotherapy (mannitol 20% or hypertonic saline) and temporary hypocapnia may be used 1, 3
- PaCO₂ should be maintained between 35-40 mmHg (4.5-5.0 kPa) during interventions for life-threatening hemorrhage or emergency neurosurgery 1, 5
Individualized CPP Targets Based on Autoregulation
- Patients with preserved cerebral autoregulation may benefit from CPP-based protocols targeting higher CPP, while those with impaired autoregulation may have better outcomes with ICP-based protocols targeting lower CPP around 60 mmHg 2, 6
- The pressure reactivity index can be used as a measure of cerebral autoregulation to determine an optimal CPP (CPPopt) for individual patients 6
- Recent research suggests that CPPopt represents an alternative target for cerebral hemodynamic optimization following severe TBI 6
Common Pitfalls in CPP Management
- Setting CPP targets too high (>70 mmHg) may increase the risk of ARDS without improving neurological outcomes 2, 4
- Setting CPP targets too low (<60 mmHg) may lead to cerebral ischemia and worsen secondary brain injury 7, 4
- Failing to adjust the reference point for MAP measurement to the external ear tragus can lead to inaccurate CPP calculations 2, 3
Special Case: Decompressive Craniectomy
- For patients who have undergone decompressive craniectomy for TBI, some evidence suggests that the targeted CPP might potentially be lowered to 35 mmHg if ICP is maintained <25 mmHg 8
- However, this finding requires further validation before being incorporated into standard practice, and the general recommendation of CPP ≥60 mmHg should still be followed 1