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

Permissive Hypotension in Trauma Patients

In trauma patients without traumatic brain injury (TBI), target a mean arterial pressure (MAP) of 50-65 mmHg or systolic blood pressure (SBP) of 80-100 mmHg until major bleeding is controlled. 1, 2

Target Blood Pressure Parameters

For Trauma WITHOUT Brain Injury

• Target MAP: 50-65 mmHg during active hemorrhage control 1, 2
• Target SBP: 80-100 mmHg until bleeding source is controlled 1, 3
• The lower MAP target of 50 mmHg has been shown to reduce 24-hour postoperative mortality and severe coagulopathy compared to MAP 65 mmHg 1, 2
• This strategy significantly reduces blood product transfusions and total IV fluid requirements 2

Critical Exception: Trauma WITH Brain Injury

• Target MAP: >80 mmHg or SBP >100 mmHg in patients with traumatic brain injury 1
• Permissive hypotension is contraindicated in TBI and spinal cord injuries because adequate cerebral perfusion pressure is essential to prevent secondary brain injury 1
• Once ICP monitoring is available, maintain cerebral perfusion pressure (CPP) ≥60 mmHg 1

Implementation Strategy

Initial Assessment Phase

• Rapidly assess for presence of TBI through Glasgow Coma Scale and mechanism of injury 1
• Identify patients with pre-existing chronic hypertension or advanced age, as these populations may require modified targets 1
• Initiate crystalloid resuscitation while preparing for definitive hemorrhage control 1

Resuscitation Targets by Clinical Context

Penetrating trauma with hemorrhagic shock:

• Use lower MAP target (50 mmHg) more aggressively 1, 2
• Evidence shows particular benefit in this population with reduced early postoperative mortality 1, 2

Blunt trauma with hemorrhagic shock:

• Target MAP 65 mmHg or SBP 80-90 mmHg 1, 3
• Evidence for benefit is less robust than penetrating trauma but strategy remains recommended 1

Polytrauma with TBI:

• Abandon permissive hypotension strategy entirely 1
• Maintain MAP >80 mmHg to ensure adequate cerebral perfusion 1

Duration and Transition

• Maintain permissive hypotension only until hemorrhage control is achieved 1, 2
• Lower blood pressure values should be tolerated "for the shortest possible time" during difficult intraoperative bleeding control 1
• Once bleeding is controlled, transition to standard resuscitation targets (MAP ≥65 mmHg) 3

Physiologic Rationale

The permissive hypotension strategy works by:

• Avoiding hydrostatic pressure increases that dislodge clots 1
• Preventing dilutional coagulopathy from excessive crystalloid administration 1
• Reducing hypothermia from large-volume fluid resuscitation 1
• Patients receiving hypotensive resuscitation (MAP 50 mmHg) had significantly lower international normalized ratio (INR) and less severe coagulopathy than those targeted to MAP 65 mmHg 2

Critical Pitfalls to Avoid

Do NOT Use Permissive Hypotension In:

• Traumatic brain injury patients - requires MAP >80 mmHg 1
• Spinal cord injury patients - adequate perfusion pressure is crucial 1
• Elderly patients with chronic hypertension - may require higher baseline pressures for adequate organ perfusion 1
• Patients with limited cardiovascular reserve from pre-existing heart disease 1

Avoid Excessive Pre-hospital Fluid Administration

• Pre-hospital crystalloid volumes >2,000 ml are associated with >40% coagulopathy incidence 1
• Volumes >3,000 ml result in >50% coagulopathy rates 1
• Low-volume pre-hospital resuscitation (0-1,500 ml) shows higher survival in multiply-injured patients with ISS ≥16 1

Monitoring During Permissive Hypotension

• Continuously monitor MAP via arterial line when possible 3
• Assess tissue perfusion markers: lactate, base excess, urine output 3
• Monitor hemoglobin levels, targeting >7 g/dL during hemorrhage control (higher threshold in elderly or cardiac disease) 1
• Maintain platelet count >50,000/mm³ for hemorrhage control 1

Evidence Quality Considerations

The strongest evidence comes from a randomized controlled trial comparing MAP targets of 50 mmHg versus 65 mmHg in trauma patients with hemorrhagic shock, which demonstrated reduced early postoperative mortality and coagulopathy with the lower target 2. However, this study included predominantly penetrating trauma patients. The European Trauma Guidelines provide Grade 1C recommendations for SBP 80-100 mmHg targets, acknowledging the evidence base is not as robust as desired but represents current best practice 1. The absolute contraindication in TBI is supported by strong physiologic rationale and consensus guidelines, though based on Grade 1C evidence 1.