Is proning (prone positioning) safe in patients with Traumatic Brain Injury (TBI) and Acute Respiratory Distress Syndrome (ARDS)?

Proning in TBI Patients with ARDS

Prone positioning can be performed in TBI patients with ARDS when intracranial pressure (ICP) is continuously monitored, ICPs are stable, there is no mass effect from hematoma or edema, and the head is maintained in a centered position—though expect ICP to rise by approximately 5 mmHg while oxygenation dramatically improves. 1

Key Physiological Trade-offs

When you prone a TBI patient with ARDS, you must accept certain predictable changes:

• ICP increases significantly: Expect baseline ICP to rise from approximately 9-12 mmHg to 14-15 mmHg 1
• Oxygenation improves dramatically: PaO2 typically increases by 25-30 mmHg or more 1, 2
• Cerebral perfusion pressure (CPP) effects are variable: Some studies show CPP decreases slightly (73 to 68 mmHg), others show improvement (66 to 73 mmHg), and some show no change 1
• Brain tissue oxygenation (PbtO2) improves: Increases from approximately 27 to 32 mmHg 1

Absolute Requirements Before Proning

You must have these in place before attempting prone positioning in TBI:

• Continuous ICP monitoring with ability for CSF diversion 1
• Stable baseline ICP (not actively elevated or requiring escalating therapy) 1
• No mass effect from intracranial hematoma or cerebral edema 1
• Head positioning protocol: Maintain head in centered position, avoid lateral rotation 1
• Adequate sedation: One study noted immediate ICP spike in an under-sedated patient, highlighting the need for deep sedation during positioning 1

Contraindications That Should Stop You

The 2024 Intensive Care Medicine guideline lists increased ICP as a relative contraindication requiring individual risk-benefit assessment 1. However, the more nuanced 2020 Critical Care guideline on neurocritical care provides clearer direction: brain injury without ICP monitoring is an absolute contraindication 1.

Additional absolute contraindications include:

• Open abdomen 1
• Spinal instability 1
• Hemodynamically significant cardiac arrhythmias 1
• Shock states (stabilize first) 1

Practical Implementation Strategy

Step 1: Optimize before proning

• Stabilize hemodynamics and optimize volume status 1
• Ensure vasopressor therapy is stable (not a contraindication) 1
• Deepen sedation to prevent ICP spikes during positioning 1

Step 2: During prone positioning

• Monitor ICP continuously throughout the maneuver 1
• Keep head centered, avoid lateral rotation 1
• Apply for 16-20 hours per day for maximum benefit 1, 2
• Use lung-protective ventilation (tidal volume 4-8 mL/kg PBW) 2

Step 3: Monitoring thresholds

• If ICP rises above 20 mmHg persistently, consider pharmacologic intervention (mannitol) 3
• If CPP falls below 60 mmHg, increase MAP with vasopressors 1
• Continue prone positioning if oxygenation improves (PaO2/FiO2 increases) 1

Evidence Quality and Limitations

The evidence supporting prone positioning in TBI with ARDS is limited to small observational studies and case series 1, 4. Critically, none of the studies specifically examined patients with both TBI and ARDS—they included TBI or subarachnoid hemorrhage patients with various lung pathologies 1. The largest study included only 29 patients 1. No randomized controlled trials exist for this specific population 4.

When the Risk-Benefit Favors Proning

Prone positioning is most justified when:

• Severe ARDS (PaO2/FiO2 < 150 mmHg) where mortality benefit is established in general ARDS 2
• Refractory hypoxemia despite optimized ventilator settings 5
• Early in TBI course before peak delayed cerebral ischemia period when ICP is more stable 1
• No alternative rescue therapies have succeeded 6

Common Pitfalls to Avoid

• Proning without ICP monitoring: This is unsafe and should never be attempted 1
• Inadequate sedation during positioning: Can cause acute ICP spikes 1
• Lateral head rotation: Impairs venous drainage and worsens ICP 1
• Abandoning prone positioning after one attempt: Consider at least two attempts before declaring failure 1
• Ignoring pressure ulcer risk: Examine vulnerable areas regularly as prone positioning significantly increases pressure ulcer risk (RR 1.22) 1, 2

Alternative Considerations

If prone positioning is too high-risk, consider these rescue therapies for ARDS in TBI patients:

• Neuromuscular blocking agents (most commonly used rescue therapy) 5
• Recruitment maneuvers 5
• Inhaled pulmonary vasodilators 5
• Extracorporeal membrane oxygenation as last resort 4, 5