Critical Care Medicine-Neurologic Disorders>>>>>Acute Respiratory Distress Syndrome
Question 3#

A 29-year-old woman is admitted to the floor with a productive cough and fevers; her influenza swab is positive, and chest radiograph demonstrates bilateral patchy pulmonary opacities. She develops progressive hypoxemic respiratory failure requiring intubation on the first day of admission. On transfer to the ICU, her initial arterial blood gas shows:

What is the next best step?

A. Ventilation with tidal volumes 4 to 6 mL/kg and PEEP >5
B. Initiate venovenous ECMO
C. Obtain a chest CT
D. Blood cultures and broad spectrum antibiotics

Correct Answer is A

Comment:

Correct Answer: A

ARDS impacts as many as 10% of patients admitted to the ICU and 23% of mechanically ventilated patients, with a mortality of 46% in patients with severe ARDS. This patient clearly meets the diagnosis of severe ARDS by the Berlin criteria, which include:

For all patients with ARDS, NHBI ARDS Network guidelines strongly suggest ventilation with low tidal volumes (goal 4-6 mL/kg predicted body weight) with plateau pressures <30 cm H2O and a minimum of PEEP 5 cm H2O. In addition, patients should receive conservative fluid management, which has been shown to shorten the duration of assisted ventilation.

Venovenous ECMO can be used to support patients with severe ARDS when conventional therapy is insufficient to correct severe hypoxemia (PaO2 :FiO2 <80) or hypercapnia (pH <7.20.) An increasing number of centers use ECMO in ARDS, particularly after 2009 H1N1 influenza A epidemic, where the patient population was typically young and otherwise healthy. Initial study of ECMO use for ARDS in patients with H1N1 found a mortality of 21%, leading to speculation that early initiation of ECMO may improve mortality. The EOLIA trial published in 2018, however, showed no mortality benefit with early initiation of ECMO as compared to ARDS Network mechanical ventilation with conventional rescue strategies that included ECMO.

A chest CT can be useful to confirm ARDS when chest radiographs fail to demonstrate opacities consistent with the diagnosis, given the heterogeneity of radiographic presentation, but it is not the next best step in this hypoxic patient. Likewise, although she will need blood cultures to rule out a superimposed bacterial pneumonia on viral influenza, improving oxygenation takes priority.

References:

  1. Thompson BT, Chambers RC, Liu KD. Acute respiratory distress syndrome. N Engl J Med. 2017;377:562-572.
  2. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308.
  3. Thompson BT, Bernard GR. ARDS network (NHLBI) studies – successes and challenges in ARDS clinical research. Crit Care Clin. 2011;27(3):459-468. doi:10.1016/j.ccc.2011.05.011.
  4. Davies A, Jones D, Bailey M, et al. Extracorporeal membrane oxygenation for 2009 influenza A(H1N1) acute respiratory distress syndrome. JAMA. 2009;302:1888-1895.
  5. Combes A, Hajage D, Capellier G, et al. Extracorporeal membrane oxygenation for severe acute respiratory distress syndrome. N Engl J Med. 2018;378:1965-1975.