Acute respiratory distress syndrome: what's evidence based and what's not?

This question was recently addressed in a review published in Baylor University Medical Center Proceedings.

The review opens with a discussion of definitions and criteria. It is important to note that the recently adopted Berlin criteria have placed ARDS into three categories, refined the radiographic definitions and eliminated the old designation ALI. The category distinctions are essential in considering various treatment options and discussing current research literature.

Below is a listing of treatment modalities under popular discussion and their current status.

Low tidal volume ventilation

Mortality benefit in ARDSnet trial.

Status: evidence based.

High peep

Although no benefit was seen in the ARDSnet (ALVEOLI) trial a subsequent meta-analysis that included other studies showed a mortality benefit for moderate and severe ARDS.

Status: evidence based for moderate or severe ARDS.

High frequency oscillation

No benefit, possible harm in clinical studies.

Status: not evidence based, not recommended.

Airway pressure release ventilation

No mortality benefit but improvement in other measures.

Status: evidence based for lower level outcomes.

ECMO

The CESAR study showed a mortality benefit in severe ARDS but there were methodologic concerns. There has been extensive lower level experience.

Status: evidence based for severe ARDS but caveats apply. Widely considered a rescue modality.

Inhaled vasodilator therapy

No clear benefit.

Status: not evidence based.

Recruitment maneuvers

No clear benefit.

Status: not evidence based but sometimes considered as a rescue modality.

Prone positioning

Mortality benefit demonstrated for patients with a PO2 to FIO2 ratio of less than 150.

Status: evidence based for patients selected on the basis of PO2 to FIO2 less than 150 (does not fit neatly into the Berlin classification).

Neuromuscular blockade

Mortality benefit early in severe ARDS, used for 48 hours. Note: steroids were given to less than half the patients in both groups in the major trial with no significant difference in usage or incidence of prolonged paralysis, between groups.

Status: evidence based for brief usage early in severe ARDS.

Steroids

This has been a topic of controversy and mixed reports but overall the evidence points to a mortality benefit if used early in moderate or severe ARDS.

Status: Evidence based for early use in moderate or severe ARDS and recommended by a recent consensus statement.