What is the target mean arterial pressure (MAP) for permissive hypotension in trauma patients?

Target Mean Arterial Pressure for Permissive Hypotension in Trauma Patients

In trauma patients without traumatic brain injury (TBI), the recommended target for permissive hypotension is a mean arterial pressure (MAP) of 50-60 mmHg (corresponding to systolic blood pressure of 80-90 mmHg) until major bleeding has been controlled. 1

General Principles of Permissive Hypotension

• Permissive hypotension involves a restricted volume replacement strategy that maintains lower-than-normal blood pressure until bleeding is controlled 1
• This approach replaces conventional aggressive fluid resuscitation, which can lead to clot disruption, dilutional coagulopathy, and increased bleeding 2
• Meta-analyses of both randomized controlled trials and retrospective studies demonstrate decreased mortality with permissive hypotension compared to traditional aggressive volume replacement targeting normotension 1, 2

Specific MAP Targets

Patients WITHOUT Traumatic Brain Injury:

• Target MAP: 50-60 mmHg (systolic BP 80-90 mmHg) 1
• This restricted target should be maintained until major bleeding has been stopped 1
• If fluid resuscitation fails to achieve this target, norepinephrine should be administered as the first-line vasopressor 1

Patients WITH Traumatic Brain Injury:

• Target MAP: ≥80 mmHg 1
• Higher MAP is crucial in TBI to ensure adequate perfusion pressure and tissue oxygenation of the injured central nervous system 1

Evidence Supporting Permissive Hypotension

• A meta-analysis of randomized controlled trials found a survival benefit with permissive hypotension in trauma patients with hemorrhagic shock (pooled odds ratio 0.70,95% CI 0.53-0.92) 2
• Several retrospective studies demonstrated that aggressive resuscitation techniques often result in increased mortality, damage control laparotomy, coagulopathy, multiorgan failure, nosocomial infections, increased transfusion requirements, and prolonged ICU stays 1

Important Considerations and Contraindications

• Permissive hypotension is contraindicated in patients with TBI and spinal injuries due to the need for adequate cerebral perfusion 1
• The approach should be used cautiously in elderly patients 1
• It may be contraindicated in patients with chronic arterial hypertension 1
• Rapid bleeding control is particularly important in patients with contraindications to permissive hypotension 1

Monitoring During Permissive Hypotension

• Frequent assessment of end-organ perfusion is essential, including:
  • Mental status
  • Capillary refill
  • Urine output
  • Extremity perfusion
  • Lactate levels
  • Central venous oxygen saturation
  • End-organ function 1
• Blood lactate should be used to estimate and monitor the extent of bleeding and tissue hypoperfusion 1
• If lactate is unavailable, base deficit may represent a suitable alternative 1

Vasopressor Use

• If restricted volume replacement fails to achieve target blood pressure, norepinephrine (0.01-0.5 μg/kg/min) is recommended as the first-line vasopressor 1
• Dobutamine should be infused in the presence of myocardial dysfunction 1
• Vasopressin can be considered as a second-line agent to be added to norepinephrine 1

Conclusion

The concept of permissive hypotension with a target MAP of 50-60 mmHg (systolic BP 80-90 mmHg) in trauma patients without TBI represents a damage control resuscitation strategy that has been shown to improve outcomes compared to traditional aggressive fluid resuscitation. This approach should be maintained until major bleeding is controlled, with appropriate modifications for patients with TBI or other contraindications.