Summary of Rescue Therapies for Refractory Hypoxemia (6 P’s of refractory hypoxemia)
• Pee: Consider diuresis to reduce pulmonary edema (see “conservative fluid management”)
• PEEP: Optimize PEEP (see “PEEP” above)
• Paralysis: Early paralysis within 48 hours of ARDS onset (see “neuromuscular blockade” above)
• Pulmonary Vasodilators: Start with iNO trial and if effective, use inhaled Epoprostenol.
o Should see at least 15% ↑ in PaO2 with iNO, otherwise do not initiate therapy due to cost and risks, including hypotension
o ↓ V/Q mismatch by selectively dilating vessels that perfuse well-ventilated lung; also ↓ PVR and ↓ RV afterload
o No mortality benefit but may improve oxygenation in first 24hrs (Cochrane 2010;7:CD002787) and total lung capacity at 6 months.
• Prone positioning: ↓ V/Q mismatch by ↓ compressive atelectasis from heart and diaphragm -> more homogenous ventilation -> ↑ alveolar recruitment -> ↓ regional volutrauma and ↑ compliance
o ↓ 28d (16% vs 32.8%) and ↓ 90d mortality (23.6 vs 41%) in pts with PaO2/FiO2 <150 and mechanical ventilation for ARDS for <36 hours; patient must be proned for at least 16 consecutive hours per day
• Perfusion (ECMO): Consider for severe, refractory hypoxemia if ventilated <7days; for details see ECMO section.
o Unclear if mortality benefit attributable to ECMO itself vs. transfer to specialized center
o Call for evaluation by the ECMO (SHOCK) Team (typically the CVICU attending)
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