Is maintaining a mean arterial pressure (MAP) within 25% of baseline blood pressure (BP) beneficial?

Maintaining MAP Within 25% of Baseline Blood Pressure: Evidence and Recommendations

There is no strong evidence that maintaining mean arterial pressure (MAP) within 25% of baseline blood pressure is beneficial for patient outcomes. Instead, current guidelines recommend specific absolute MAP targets based on clinical context rather than relative changes from baseline.

Current Evidence-Based MAP Targets

General Critical Care and Perioperative Settings

• The Surviving Sepsis Campaign guidelines recommend maintaining MAP ≥65 mmHg as the initial target in septic shock patients 1
• The Perioperative Quality Initiative (POQI) consensus statement recommends keeping intraoperative MAP ≥60 mmHg to prevent organ injury 1
• For patients with elevated venous or compartment pressures, the POQI recommends increasing MAP targets (strong recommendation, moderate-quality evidence) 1

Special Populations

• Hypertensive patients: The POQI trial showed that patients with chronic hypertension may benefit from higher MAP targets (75-80 mmHg) to reduce the need for renal replacement therapy 1
• Elderly patients: A pilot trial suggested that in patients >75 years, targeting a lower MAP (60-65 mmHg vs 75-80 mmHg) may reduce mortality 1
• Cardiac patients: For patients with advanced heart failure, maintaining trans-kidney perfusion pressure (MAP-CVP) >60 mmHg is recommended 1

Limitations of Relative MAP Targets

The concept of maintaining MAP within 25% of baseline has several limitations:

1. Lack of evidence: No major guidelines specifically recommend maintaining MAP within 25% of baseline for general patient populations
2. Baseline determination challenges: Determining true baseline BP is difficult as preoperative values may be affected by anxiety, medications, or white coat effect 1
3. Inconsistent measurement: There are significant differences between measured and calculated MAP values, which can vary by device 2

Organ-Specific Considerations

Renal Protection

• A multicenter trial showed that targeting MAP of 85 mmHg vs 65 mmHg in septic shock patients with chronic hypertension reduced the need for renal replacement therapy 1
• Trans-kidney perfusion pressure (MAP-CVP) >60 mmHg is recommended for patients with advanced heart failure 1

Cerebral Protection

• In acute ischemic stroke, guidelines recommend lowering MAP by only 15% in the first 24 hours if BP is very high (>220/120 mmHg) 1
• For patients receiving thrombolysis, BP should be lowered to <185/110 mmHg before treatment 1

Cardiac Protection

• In hypertensive emergencies with acute coronary events, immediate reduction to systolic BP <140 mmHg is recommended 1
• For acute aortic dissection, immediate reduction to systolic BP <120 mmHg and heart rate <60 bpm is recommended 1

Evidence-Based Approach to MAP Management

Rather than using a relative target (within 25% of baseline), consider:

1. Use absolute MAP thresholds based on patient condition:

   • General critical care: MAP ≥65 mmHg 1
   • Perioperative: MAP ≥60 mmHg 1
   • Hypertensive patients: Consider higher targets (75-80 mmHg) 1

2. Adjust based on clinical context:

   • Elevated venous pressure: Increase MAP target 1
   • Advanced age (>75 years): Consider lower targets (60-65 mmHg) 1
   • Specific organ protection needs (brain, heart, kidneys)

3. Monitor for adequacy of perfusion using:

   • Lactate levels
   • Urine output
   • Mental status
   • Peripheral perfusion

Conclusion

While maintaining MAP within a certain percentage of baseline is conceptually appealing, current evidence supports using specific absolute MAP targets based on clinical context rather than relative changes from baseline. The focus should be on maintaining adequate organ perfusion while avoiding excessive vasopressor use, which may increase cardiac afterload and worsen outcomes.