Acute Respiratory Distress Syndrome
Marie-Christine Aubry, M.D.
Allen P. Burke, M.D.
Definition
Acute respiratory distress syndrome (ARDS) is defined clinically and is, as such, not a pathologic term. Until recently, the clinical diagnostic criteria of the American-European Consensus Conference (AECC) were used, namely, bilateral pulmonary infiltrates on chest radiograph, a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2) of <200, and absence of clinical evidence of left atrial hypertension (if measured, the pulmonary capillary wedge pressure is ≤18 mm Hg). The term “acute lung injury” was a synonym, with a higher cutoff of PaO2/FiO2 set at 300.1 The criteria have been modified by the “Berlin Definition,” an initiative of the European Society of Intensive Care Medicine with endorsement by the American Thoracic Society and the Society of Critical Care Medicine2 (Table 21.1). The new criteria grade the degree of ARDS largely based on the PaO2/FiO2 into three groups, and remove the term “acute lung injury.” These changes resulted in a better predictive validity for mortality than the prior AECC criteria.
Clinical Findings
The estimated incidence of ARDS in the United States is 17 to 64 per 100,000 population per year.3 Patients with ARDS typically present with rapid (within 1 week) onset of respiratory failure, with profound dyspnea and tachypnea, usually requiring mechanical ventilation. Arterial hypoxemia refractory to treatment with supplemental oxygen is a characteristic feature.
A risk factor is usually present (Table 21.2). The presence of multiple predisposing factors increases the risk, as does the presence of underlying chronic lung disease. Sepsis represents the highest risk for progression to ARDS. Nearly 50% of patients with severe sepsis and septic shock will require endotracheal intubation and mechanical ventilation because of ARDS.4
Severe burns, such as those experienced by US servicemen suffering casualties in Iraq and Afghanistan, result in ARDS in about one in three patients.5
The risk for developing ARDS after general surgery has been estimated at 0.2%. Preoperative risk factors for ARDS development included American Society of Anesthesiologist status 3 to 5 (odds ratio [OR] 19), emergent surgery (OR 9), renal failure (OR 2), chronic obstructive pulmonary disease (OR 2), and intraoperative erythrocyte transfusion (OR 5).6
TABLE 21.1 The Berlin Definition of ARDS | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||
After thoracotomy for lung cancer, the risk is <2% of overall for the development of ARDS, but increases dramatically if there is preoperative computed tomographic evidence of interstitial pulmonary fibrosis.5
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
