What is a good cerebral perfusion pressure (CPP)?

Optimal Cerebral Perfusion Pressure (CPP)

In adults with traumatic brain injury, a cerebral perfusion pressure between 60 and 70 mmHg should be maintained in the absence of multi-modal monitoring to optimize neurological outcomes. 1

Understanding Cerebral Perfusion Pressure

• CPP is calculated as the difference between mean arterial pressure (MAP) and intracranial pressure (ICP): CPP = MAP - ICP 1
• The reference point for measuring MAP should be placed at the external ear tragus 1, 2
• CPP represents the pressure gradient driving cerebral blood flow, which is critical for meeting the metabolic needs of brain tissue 3

Evidence-Based CPP Targets

• CPP < 60 mmHg is associated with poor neurological outcomes due to inadequate cerebral blood flow 1
• CPP > 70 mmHg is not recommended routinely as it has been associated with:
  • 5 times higher incidence of respiratory distress syndrome 1
  • No improvement in neurological outcomes compared to lower targets 1, 4
  • Potential worsening of vasogenic cerebral edema when CPP exceeds 90 mmHg 1

Special Considerations for CPP Management

• Recent evidence suggests that the relationship between CPP and outcomes is asymmetric - patients are more vulnerable to CPP reductions below personalized thresholds than elevations above them 5
• Cerebral autoregulation status affects optimal CPP targets:
  • Patients with preserved autoregulation may benefit from CPP-based protocols (targeting higher CPP) 1
  • Patients with impaired autoregulation may have better outcomes with ICP-based protocols (targeting lower CPP around 60 mmHg) 1, 6

Practical CPP Management in Clinical Settings

• For most patients with severe traumatic brain injury, maintain CPP between 60-70 mmHg 1
• When ICP monitoring becomes available, maintain CPP ≥ 60 mmHg 1
• In cases of cerebral herniation or threatened intracranial hypertension:
  • Use osmotherapy (mannitol 20% or hypertonic saline at 250 mOsm over 15-20 minutes) 1
  • Temporary hypocapnia may be used during emergency situations, but prolonged hypocapnia should be avoided 1

Common Pitfalls in CPP Management

• Setting CPP targets too high (>70 mmHg) may increase risk of ARDS without improving neurological outcomes 1, 4
• Setting CPP targets too low (<60 mmHg) may lead to cerebral ischemia and worsen secondary brain injury 1, 3
• Failing to adjust the reference point for MAP measurement to the external ear tragus can lead to inaccurate CPP calculations 1, 2
• Not considering individual patient factors such as cerebral autoregulation status when determining CPP targets 6, 5

Emerging Concepts in CPP Management

• Advanced neuromonitoring techniques may allow for individualized CPP targets based on:
  • Pressure reactivity index (PRx) to assess cerebral autoregulation 6, 5
  • Optimal CPP (CPPopt) derived from autoregulation status 6, 5
• Recent research suggests that even small decreases below individualized CPPopt are consistently linked to worse outcomes, while higher-than-CPPopt levels generally don't show association with worse outcomes 5