Acute Respiratory Distress Syndrome and Refractory Hypoxemia: Selecting Evidence-Based Treatments

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Researchers examined current mechanical ventilation strategies for ARDS and refractory hypoxemia.
Researchers examined current mechanical ventilation strategies for ARDS and refractory hypoxemia.

Clinical practice guidelines and knowledge translation strategies are needed for the management of patients with acute respiratory distress syndrome (ARDS) and refractory hypoxemia, according to the results of a 1-year prospective cohort study published in the Annals of the American Thoracic Society. The authors of the study state that mechanical ventilation strategies currently being used in patients with moderate to severe ARDS are not in line with lung-protective ventilation approaches supported by clinical evidence.

The researchers examined current mechanical ventilation strategies for adults with ARDS and refractory hypoxemia. A total of 664 adults undergoing mechanical ventilation who had moderate (n=222; 33%) or severe (n=442; 67%) ARDS, and who required fraction of expired oxygen levels ≥0.50 were enrolled in the study between March 2014 and February 2015 from 24 different hospital intensive care units.

On day 1 of the study, mean tidal volume (VT) was 7.5±2.1 mL/kg predicted body weight (n=625); 79% (496 of 625) of these patients received VT >6 mL/kg. Mean positive end-expiratory pressure (PEEP) was 10.5±3.7 cmH2O (n=653), and 87% (568 of 653) of these participants received PEEP <15 cmH2O.

The use of adjunctive treatments was reported in 66% (440 of 664) of patients, including neuromuscular blockers (n=276; 42%), pulmonary vasodilators (n=118; 18%), prone positioning (n=67; 10%), high-frequency oscillatory ventilation (n=29; 4%), and extracorporeal life support (n=29; 4%).

Refractory hypoxemia, which was defined as partial pressure of arterial oxygen <60 mm Hg on fraction of expired oxygen 1.0, was reported in 21% (138 of 664) of patients. At the onset of refractory hypoxemia, mean VT was 7.1±2.0 mL/kg, and 26% (32 of 138) of these patients received VT >8 mL/kg.

Mean PEEP was 12.1±4.4 cmH2O (n=135), and approximately 74% of patients received PEEP <15 cmH2O. In those with refractory hypoxemia, 91% (126 of 138) received treatment adjuncts, including an increased use of neuromuscular blockers (n=96; 70%), pulmonary vasodilators (n=62; 45%), and prone positioning (n=37; 27%).

The researchers concluded that patients with moderate to severe ARDS receive adjunctive therapies often, which is particularly true of those with refractory hypoxemia. Ironically, those treatments with less evidence supporting their use (eg, pulmonary vasodilators) were overused, whereas those with more evidence endorsing their use (eg, neuromuscular blockade and prone positioning) were underused. These findings provide useful information regarding contemporary ARDS management strategies.

Reference

Duan EH, Adhikari NKJ, D'Aragon F, et al; Canadian Critical Care Trials Group. Management of ARDS and refractory hypoxemia: a multicenter observational study [published online September 14, 2017]. Ann Am Thorac Soc. doi: 10.1513/AnnalsATS.201612-1042OC.

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