CURRENT Essentials of Critical Care.pdf

Chapter 8 Respiratory Failure 93■■■Acute Respiratory Distress Syndrome (ARDS)Essentials of Diagnosis• Severe hypoxemia refractory to supplemental oxygen(PaO 2 /FIO 2 200–300); acute diffuse chest radiograph infiltratesconsistent with noncardiogenic pulmonary edema (increasedlung permeability); no evidence of heart failure; if measured,normal or low pulmonary artery wedge pressure• 75–80% due to sepsis, pneumonia, aspiration of gastric contents,severe trauma; other causes: fat embolism, pancreatitis, transfusionrelated lung injury, amniotic fluid embolism• Mortality 30–60%; highest in sepsis, elderly, multiorgan systemfailure; due to nonrespiratory organ failure, infection; rarely respiratoryfailureDifferential Diagnosis• Cardiogenic pulmonary edema• Severe extrapulmonary right-to-left shunt (intracardiac shunt)• Severe localized pneumonia or atelectasis without diffuse lunginvolvementTreatment• Treat underlying disease (sepsis, trauma, pneumonia, pancreatitis)• High oxygen concentrations (FIO 2 0.4)• Endotracheal intubation, mechanical ventilation needed for increasedwork of breathing• Positive end-expiratory pressure• Low tidal volume (6 mL/kg) improves survival; may lead tohypercapnia (keep f 35/min)• Minimal fluid intake and diuretics may help reduce pulmonaryedema; may not be compatible with treating underlying diseases• Complications of high FIO 2 : lung injury; high positive end-expiratorypressure (PEEP): low cardiac output, hypotension,pneumothorax, lung injury■ PearlAttack rate of ARDS for patients with similar underlying disordersmay be higher in chronic alcoholics, smokers, and the elderly.ReferenceWare LB et al: The acute respiratory distress syndrome. N Engl J Med2000;342:1334. [PMID: 10793167]