Acute respiratory distress syndrome (ARDS) is the result of a diffuse inflammatory lung injury, which leads to increased pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue. (1) The causes of ARDS are multiple and include sepsis –the most common–, pneumonia, aspiration, and severe trauma. The Berlin criteria (1) define ARDS according to four key features: timing (within 1 week of a known clinical insult or new or worsening respiratory symptoms); chest imaging (presence of bilateral opacities that cannot be fully explained by effusions, lobar/lung collapse, or nodules); edema due to primary respiratory failure and not cardiac failure or fluid overload; the PaO2/FIO2 ratio. This latter feature is used to define the severity of ARDS as mild, moderate or severe. In a large observational study of 29,144 patients admitted to 459 intensive care units (ICUs) in 50 countries, 10% had ARDS. The overall mortality rate was 40%, increasing from 35% in patients with mild ARDS, to 40% in moderate and 46% in severe ARDS. (2) Although several studies have suggested a trend towards lower mortality rates over time (3-7), hospital mortality rates remain high (1, 2) and long-term morbidity is considerable. (8-10)
Many potential pharmacological agents, both inhaled (11) and systemic, have been assessed for use in patients with ARDS (table 1), but none has consistently been shown to improve mortality. As such, management essentially relies on treatment of the underlying cause, especially sepsis and limiting further lung injury by providing appropriate protective lung ventilation and avoiding highly positive fluid balances. (12) Here we will briefly consider the evidence base (or lack of) for these approaches and for some of the other therapeutic approaches that have been proposed.
Dr Vincent has no conflicts of interest to declare regarding this manuscript
Key words: acute respiratory distress syndrome