A 36-year-old man is admitted to the ICU intubated status post polytrauma, with trauma burden including multiple lacerations over the ventral chest wall and an uncleared c-spine. He develops progressive hypoxemia over the first 12 hours of admission, with PaO2 :FiO2 ratios decreasing to <150 on FiO2 100%. Mechanical ventilation with tidal volumes 6 mL/kg and PEEP titrated to 12 cm H2O is initiated; however, arterial blood gas persistently shows pH 7.25 with PaCO2 68 and PaO2 67 on FiO2 100% over the subsequent 6 hours. The patient is adequately sedated, paralyzed, and demonstrates no ventilator asynchrony.
What is the next best step?
A. Use esophageal pressure measurements to titrate PEEPCorrect Answer: B
Mechanical ventilation can perpetuate lung injury in ARDS by overdistending ventilated alveoli and causing atelectrauma be repeated alveolar opening and collapse if PEEP is insufficient to maintain patency at end expiration. Venovenous ECMO can be used to bypass the pulmonary circuit in severe ARDS, performing gas exchange and minimizing further lung injury. It is typically a salvage therapy utilized when other rescue strategies such as prone positioning or neuromuscular blockade have failed or are contraindicated. Criteria for ECMO initiation include acute, reversible lung injury when conventional therapy is insufficient to sustain life in the setting of severe hypoxemia (PaO2 :FiO2 <80) or uncompensated respiratory acidosis (pH <7.20). Contraindications include irreversible lung disease with no indication for lung transplant and intracranial bleeding.
In this stem, the patient has already shown no improvement after paralysis to ensure ventilator synchrony. An unstable vertebral fracture is an absolute contraindication to proning, whereas significant lacerations or burns over the ventral chest or abdomen are a relative contraindication. Inhaled nitric oxide results in transient improvement in oxygenation in patients with ARDS while therapy is continued but has shown no benefit on mortality and is associated with acute kidney injury. Esophageal pressure measurement can be used to individualize PEEP titration for improved alveolar recruitment, particularly in patients with decreased extrapulmonary compliance, such as those with ascites or obesity. However, it is unlikely to salvage the degree of refractory hypoxemia and respiratory acidosis seen in this patient. Thus, venovenous ECMO seems to be the next best strategy in this patient.
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