What are the current Mean Arterial Pressure (MAP) targets in the management of traumatic spinal injury?

Mean Arterial Pressure Targets in Traumatic Spinal Cord Injury

Direct Recommendation

Maintain MAP ≥70 mmHg during the first week after traumatic spinal cord injury, with continuous arterial line monitoring, recognizing that higher targets (MAP >85 mmHg) lack sufficient evidence despite being recommended by some societies. 1

Evidence-Based MAP Target Ranges

Primary Target: MAP ≥70 mmHg

The French guidelines from 2020 provide the most conservative and evidence-based recommendation, suggesting MAP ≥70 mmHg during the first week post-injury. 1 This recommendation acknowledges that there is insufficient level of evidence to recommend MAP levels over 70 mmHg, despite more aggressive targets being proposed elsewhere. 1

The rationale for this 70 mmHg threshold comes from:

• A study of 92 patients showing spinal cord perfusion pressure >50 mmHg correlated with better 6-month neurological outcomes, with analysis determining optimal MAP >70 mmHg 1
• Correlation between MAP level and neurological improvement appearing at MAP values >70-75 mmHg, though this correlation only existed for 2-3 days after admission 1
• A small retrospective study (n=17) demonstrating reverse correlation between time spent with MAP <65-70 mmHg and neurological improvement 1

Alternative Target: MAP >85 mmHg (Weaker Evidence)

The American Association of Neurological Surgeons/Congress of Neurological Surgeons recommends targeting supra-physiological MAP >85 mmHg within the first 5-7 days. 1, 2 However, this recommendation is essentially based on two prospective interventional studies, neither of which had a control group. 1 The 2019 CNS guidelines acknowledge that scientific data supporting MAP augmentation are mainly derived from cervical SCI studies. 2

Critical Duration of MAP Management

The most critical window for MAP augmentation is the first 2-3 days after injury, with most guidelines recommending continuation through 5-7 days post-injury. 1, 2 The correlation between MAP level and neurological improvement during hospitalization appeared strongest in this early period and only existed for 2-3 days after admission. 1

Spinal Cord Perfusion Pressure (SCPP) as Superior Target

Recent evidence suggests that SCPP (MAP minus CSF pressure) targets of 60-65 mmHg may be superior to MAP targets alone for predicting neurological recovery. 3 A multicenter prospective trial of 92 patients found that adherence to SCPP targets, not MAP targets, was the best indicator of improved neurologic recovery. 3 However, SCPP monitoring via intradural catheters at the injury site carries increased risks of CSF leakage requiring revision surgery or pseudomeningocele. 4

Mandatory Monitoring Requirements

Continuous arterial line monitoring is essential because analysis of 74 patients with spinal cord injury showed MAP is below the determined objective 25% of the time without continuous monitoring. 1, 2 This makes intermittent cuff measurements inadequate for this population.

Pre-Hospital and Early Management Pitfalls

A critical gap exists in the pre-hospital and early admission period. A study of 40 acute tSCI patients found:

• 52% of MAP measurements were <80 mmHg at primary receiving hospitals 5
• 40% of MAP measurements were <80 mmHg in the tertiary hospital emergency room 5
• Mean calculated MAP was only 78.8 mmHg at primary hospitals despite the importance of early hemodynamic optimization 5

This highlights that patients experience many periods of relative hypotension before reaching specialized units, emphasizing the need for aggressive early management and education of non-specialist providers. 5

Vasopressor Selection

Norepinephrine appears to be the vasopressor of choice based on limited evidence suggesting it may have less risk of adverse events than dopamine. 6, 4 However, the literature on specific vasopressor selection in spinal cord injury remains limited.

Systolic Blood Pressure Threshold

Before injury assessment is completed, maintain systolic blood pressure >110 mmHg to reduce mortality. 1 Hypotension at hospital admission, defined as SBP <110 mmHg, is an independent factor of patient mortality after spinal cord injury. 1

Evidence Quality and Limitations

All current recommendations are based on Class III evidence only, with no randomized controlled trials comparing neurological outcomes at different MAP targets. 1, 6 The effect of MAP support on neurological recovery is uncertain according to low or very low quality evidence, and vasopressor use may be associated with increased rates of predominantly cardiac adverse events. 4

Practical Algorithm

1. Immediate phase (pre-hospital/ED): Maintain SBP >110 mmHg 1
2. First week post-injury: Target MAP ≥70 mmHg with continuous arterial line monitoring 1
3. Consider SCPP monitoring: If resources available, target SCPP 60-65 mmHg (MAP minus CSF pressure) 3
4. Duration: Continue aggressive MAP management for 5-7 days, with most critical period being first 2-3 days 1, 2
5. Vasopressor choice: Use norepinephrine as first-line agent 6, 4

Key Caveats

• Higher MAP targets (>85 mmHg) may be chosen by clinicians but lack robust evidence 2
• Achieving target MAP is difficult—expect to be below target 25% of the time even with aggressive management 1, 2
• Cardiac adverse events may increase with vasopressor use 4
• Transfer to specialized spinal cord injury units is strongly recommended to optimize adherence to hemodynamic targets 1