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  • Acute onset and progression within hours
  • Respiratory: Not cardiogenic clinically or by echo. PA occlusion pressure (wedge) <18 cm H2O
  • Distress: Decreased oxygenation:
    • PaO2/FiO2 <200 mm Hg
    • <300 for ALI regardless of PEEP
  • Syndrome:
    • Mortality with current management still 25–50%
    • Survivors suffer from significant morbidity and reduced quality of life because of respiratory sequelae such as chronic infections and tracheostomy
    • Pulmonary HTN and RV failure may be present:
      • Acute RV failure on echo: RV dilation and paradoxical septum motion

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  • Sepsis (30%)
  • Aspiration (36%)
  • Trauma (11%)
  • TRALI and others (burns and toxic fumes, drug overdose, drowning, acute pancreatitis)

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  • Treat underlying cause if possible (especially sepsis)
  • Sedate as little as possible
  • Respiratory management:
    • First goal: Avoid secondary lung injury with hyperinflation:
      • Low tidal volume ventilation (6 mL/kg IBW):
        • VC and PCV same efficacy. Watch TV and maintain plateau pressure (Ppl) <30 cm H2O (add 0.2 second inspiratory pause to measure Ppl)
        • Absolute mortality risk reduction from 40% to 31% with NNT = 11
    • Second goal: Optimize oxygenation and V/Q matching:
      • Place arterial line and titrate to PaO2 >60 with incremental PEEP up to 12 first and then increasing FiO2
    • Third goal: Permissive hypercapnia (accept PacO2 up to 60 mm Hg):
      • RR up to 30 if needed, but watch auto-PEEP with risk of breath stacking
      • No indication to NaHCO3 with respiratory acidosis
  • Troubleshooting: when the goals are difficult to achieve:
    • Recruitment maneuver to reopen atelectatic areas of lungs:
      • Set APL valve to 40, squeeze bag to achieve peak airway pressures of 40 cm H2O, hold for 30 seconds (8–12 seconds probably sufficient), and repeat a few times
      • May transiently improve oxygenation by opening collapsed alveoli (but also by reducing pulmonary shunt by decreasing cardiac output)
      • Watch for hypotension (usually brief, due to decrease in venous return) and pneumothorax
      • Contraindicated if elevated ICP
    • Conservative fluid strategy (ARDSNet trial in ICU setting):
      • Guided strictly by CVP, PAOP, urine output, MAP, cardiac output, and capillary refill
      • Elaborate treatment algorithm using fluid boluses, KVO fluid, dopamine, or furosemide
      • Conservative strategy improved lung function and shortened mechanical ventilation without increasing nonpulmonary organ failures
  • No proven mortality benefit but can be considered:
    • Prone position: Improves oxygenation, but does not reduce mortality
    • Steroids: May shorten course and decrease fibrosis if given <7 days (methylprednisolone 2 mg/kg per day), but may worsen mortality if given >2 weeks into ARDS. Avoid combining with NMB (risk of critical illness myo/neuropathy)
    • Inhaled nitric oxide: Improves oxygenation but not survival. May be useful with refractory hypoxemia, severe pulmonary hypertension, or RV failure
    • Inhaled surfactant/prostaglandins, ECMO for intractable hypoxemia
    • Nutritional support: Avoid hypophosphatemia; reduce CO2 with increased lipid proportion in diet
    • PA catheter not useful

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  • Use pressure-controlled-volume-guaranteed (PCVG) mode if available to optimize Vt to 6–8 mL/kg IBW while limiting Paw to 40 cm Hg and Pplateau to 30 cm Hg with paralysis. Otherwise, use PCV mode. Consider using ICU ventilator + TIVA
  • Start with PEEP of 10 cm ...

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