What are the recommended rescue strategies for a patient with acute respiratory distress syndrome (ARDS)?

Rescue Strategies in ARDS

For patients with severe ARDS and refractory hypoxemia (PaO₂/FiO₂ <150 mmHg), prone positioning for ≥16 hours daily is the most critical rescue intervention, followed by neuromuscular blockade for 48 hours, and venovenous ECMO as the ultimate rescue when PaO₂/FiO₂ remains <70 mmHg for ≥3 hours despite all other measures. 1

Primary Rescue Interventions

Prone Positioning

• Implement prone positioning immediately when PaO₂/FiO₂ falls below 150 mmHg, applying it for 16-20 hours per day. 2 This intervention reduces 28-day mortality from 32% to 16% in severe ARDS. 2
• Prone positioning redistributes lung densities, recruits well-perfused dorsal regions, reduces ventilator-induced lung injury risk, and improves ventilation/perfusion matching even when oxygenation does not visibly improve. 2
• Contraindications include open abdominal wounds, unstable pelvic fractures, spinal instability, and brain injury without intracranial pressure monitoring. 2 Well-trained staff are essential for safe implementation. 2

Neuromuscular Blockade

• Administer cisatracurium for ≤48 hours in patients with PaO₂/FiO₂ <150 mmHg to prevent patient-ventilator dyssynchrony and excessive transpulmonary pressures. 2, 1
• This strategy should be reserved for the acute phase (first 48 hours) of the most severe ARDS cases. 2
• Neuromuscular blockade prevents expiratory derecruitment by maintaining expiratory transpulmonary pressure and may have anti-inflammatory properties through nicotinic acetylcholine receptor blockade. 2
• Avoid prolonged use beyond 48 hours due to risks of ICU-acquired weakness and myopathy, especially with concomitant corticosteroids. 2

Recruitment Maneuvers

• Apply recruitment maneuvers (40 cmH₂O continuous positive airway pressure for 40 seconds) in patients with severe ARDS who have preserved chest wall mechanics and early disease (<7 days). 2, 3
• Recruitment maneuvers are most effective in patients with low lung elastance (EstL <24 cmH₂O/L) and low chest wall elastance (EstW <6 cmH₂O/L), typically within the first 1-3 days of ARDS. 3
• Do not use recruitment maneuvers in patients with prolonged ARDS (>7 days) or impaired chest wall mechanics, as they provide minimal benefit and cause significant hemodynamic compromise. 3

Advanced Rescue Therapies

Extracorporeal Membrane Oxygenation (ECMO)

• Consider venovenous ECMO as the ultimate rescue therapy when PaO₂/FiO₂ remains <70 mmHg for ≥3 hours or <100 mmHg for ≥6 hours despite optimized lung-protective ventilation, prone positioning, and neuromuscular blockade. 1, 4
• ECMO probably decreases mortality and increases ventilator-free days in severe ARDS, though it requires specialized expertise and careful patient selection. 1, 4
• Early identification of ECMO candidates is critical—transfer to an ECMO-capable center should occur before multi-organ failure develops. 5

High-Frequency Oscillatory Ventilation (HFOV)

• Do not use high-frequency oscillatory ventilation routinely in ARDS, as randomized trials show no benefit and potential harm when applied early from high pressure baselines. 2
• HFOV may have limited utility as rescue therapy only in the most severe cases (PaO₂/FiO₂ <70 mmHg) based on meta-analysis data, but evidence remains weak. 2

Supportive Rescue Measures

Fluid Management

• Implement conservative fluid strategy once shock resolves, targeting negative fluid balance to reduce pulmonary edema and improve lung function. 2, 1, 6
• Consider hemofiltration for specific indications when fluid overload contributes to refractory hypoxemia. 6

Corticosteroids

• Consider corticosteroids when initiated early (<14 days from ARDS onset) in moderate-to-severe ARDS, as this may reduce mortality. 1, 4
• Never initiate corticosteroids >14 days after ARDS onset, as late administration is associated with harm. 4
• Pulse-dose or high-dose steroids do not improve survival in early ARDS and carry significant long-term morbidity including disabling muscle weakness. 2

Inhaled Vasodilators

• Inhaled nitric oxide and prostaglandins provide short-term oxygenation improvement without proven survival benefit. 7
• These agents may serve as temporizing measures while implementing definitive rescue strategies, but should not delay prone positioning or ECMO consideration. 7

Critical Monitoring During Rescue Therapy

Hemodynamic Assessment

• Perform urgent echocardiography to detect acute cor pulmonale, which occurs in 20-25% of ARDS patients and requires specific management. 1, 4
• If acute cor pulmonale is identified, avoid further fluid administration, initiate norepinephrine to maintain MAP ≥65 mmHg, optimize oxygenation aggressively, and consider reducing PEEP if RV dysfunction is severe. 4

Ventilator Parameters

• Maintain strict adherence to lung-protective ventilation throughout rescue therapy: tidal volume 4-8 mL/kg predicted body weight, plateau pressure <30 cmH₂O (ideally <28 cmH₂O), and minimize driving pressure. 1, 6
• Use higher PEEP strategy (>12 cmH₂O) guided by ARDS Network PEEP-to-FiO₂ grid for moderate-to-severe ARDS. 1, 6
• Target SpO₂ 92-96% or PaO₂ 70-90 mmHg to avoid oxygen toxicity. 1, 4

Common Pitfalls to Avoid

• Do not delay prone positioning while attempting other interventions—it is the only rescue therapy with proven mortality reduction and should be implemented immediately when PaO₂/FiO₂ <150 mmHg. 1, 8
• Do not use noninvasive ventilation in severe ARDS, as it may delay definitive intubation and increase nosocomial transmission risk. 2
• Do not abandon lung-protective ventilation principles during rescue therapy—even with permissive hypercapnia, maintaining low tidal volumes is essential. 8
• Do not overlook non-pulmonary causes of deterioration including pulmonary embolism, pneumothorax, or ventilator-associated pneumonia when rescue therapies fail. 4, 8