What are the mean arterial pressure (MAP) targets after traumatic brain injury in adults and children?

Mean Arterial Pressure Targets After Traumatic Brain Injury

For adults with severe TBI, maintain MAP to achieve a cerebral perfusion pressure (CPP) of 60-70 mmHg, which typically requires MAP ≥80 mmHg when accounting for elevated intracranial pressure. 1

Understanding the Relationship Between MAP and CPP

The fundamental equation governing cerebral perfusion is CPP = MAP - ICP 1. This means:

• In adults with severe TBI and elevated ICP (typically 15-25 mmHg), achieving CPP of 60-70 mmHg requires MAP of approximately 75-95 mmHg 1
• The MAP measurement reference point must be at the external ear tragus for accurate CPP calculations 1
• CPP < 60 mmHg is associated with poor neurological outcomes due to inadequate cerebral blood flow 1

Adult MAP/CPP Targets: The Evidence

Maintain CPP between 60-70 mmHg as the primary target 1. The evidence supporting this includes:

• CPP > 70 mmHg is NOT recommended routinely, as it increases the risk of acute respiratory distress syndrome five-fold without improving neurological outcomes 1
• CPP exceeding 90 mmHg may worsen vasogenic cerebral edema 1
• Early hypotension (MAP ≤65 mmHg within the first 4 hours after admission) is associated with four-fold increased mortality 2
• Survivors of severe TBI had mean MAP of 80 mmHg at 4 hours post-admission, compared to 71 mmHg in non-survivors 2

Autoregulation-Based Individualization

While the standard target is CPP 60-70 mmHg, autoregulation status matters 1:

• Patients with preserved cerebral autoregulation may benefit from higher CPP targets 1
• Patients with impaired autoregulation have better outcomes with ICP-based protocols targeting CPP around 60 mmHg 1

Pediatric MAP/CPP Targets: Age-Dependent Thresholds

Pediatric TBI requires age-specific CPP targets that are lower than adults 3:

Age-Specific CPP Thresholds

• Ages 0-5 years: Maintain CPP > 40 mmHg (CPP < 30 mmHg associated with 8-fold increased risk of poor outcome) 3
• Ages 6-11 years: Maintain CPP > 50 mmHg (CPP < 35 mmHg associated with 8-fold increased risk of poor outcome) 3
• Ages 12-17 years: Maintain CPP > 60 mmHg (CPP < 50 mmHg associated with 2.35-fold increased risk of poor outcome) 3

Specific Age Targets

• 7-year-olds: Minimal CPP threshold of 60 mmHg 3
• 8-year-olds: Minimal CPP threshold of 55 mmHg 3
• 10-year-olds: Optimal CPP of 58 mmHg 3

Pediatric MAP Considerations

• MAP < 10th percentile for age during the first 12 hours is strongly associated with poor discharge outcomes 4
• MAP < 5th percentile had 42.9% poor discharge outcomes (5.3-fold increased risk) 4
• MAP 5-9th percentile had 40% poor discharge outcomes (8.5-fold increased risk) 4

Practical Algorithm for MAP Management

Step 1: Initial Resuscitation Phase (First 4 Hours)

Target MAP ≥80 mmHg during active hemorrhage or before ICP monitoring is established 5, 2:

• This higher MAP target ensures adequate cerebral perfusion when ICP is unknown
• Early hypotension (MAP ≤65 mmHg) quadruples mortality risk 2

Step 2: Once ICP Monitoring Established

Calculate and maintain CPP based on age 1:

• Adults: CPP 60-70 mmHg (adjust MAP accordingly based on measured ICP) 1
• Children: Use age-specific CPP targets listed above 3

Step 3: Avoid Excessive Pressures

• Do not routinely target CPP > 70 mmHg in adults due to ARDS risk without benefit 1
• Never allow CPP to exceed 90 mmHg as this worsens vasogenic edema 1

Critical Pitfalls to Avoid

Setting MAP targets too low (resulting in CPP < 60 mmHg in adults) leads to cerebral ischemia and secondary brain injury 1. Conversely:

• Aggressive MAP augmentation to achieve CPP > 70 mmHg increases ARDS risk five-fold without improving outcomes 1
• Failing to adjust the MAP measurement reference point to the external ear tragus causes inaccurate CPP calculations 1
• Delayed initiation of ICP monitoring and ICU admission may delay recognition of inadequate CPP 2
• In pediatric TBI, using adult CPP targets instead of age-appropriate thresholds increases poor outcomes eight-fold in younger children 3

Special Populations

Children < 2 Years Old

• ICP monitoring is underutilized but critically important in this age group 3
• This population has high incidence of raised ICP and strong association between CPP and neurological outcome 3
• Manage in pediatric trauma centers or adult centers with pediatric expertise 3

During Active Hemorrhage

• Maintain MAP ≥80 mmHg or systolic BP >100 mmHg until hemorrhage is controlled 5
• Animal models suggest MAP of 70 mmHg provides optimal balance between cerebral perfusion and hemorrhage control in combined TBI and uncontrolled hemorrhage 6