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The Management of Acute Respiratory Distress Syndrome

The Management of Acute Respiratory Distress Syndrome. 署立桃園醫院 胸腔內科 林倬睿醫師. Outlines. Introduction Ventilator strategy Adjunctive therapy Case demonstration. 定義 Definition. 急性 Acute onset 缺氧 PaO2/FiO2 < 200 mmHg CXR: bilateral infiltrates 雙側浸潤

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The Management of Acute Respiratory Distress Syndrome

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  1. The Management of Acute Respiratory Distress Syndrome 署立桃園醫院 胸腔內科 林倬睿醫師

  2. Outlines • Introduction • Ventilator strategy • Adjunctive therapy • Case demonstration

  3. 定義 Definition • 急性 Acute onset • 缺氧 PaO2/FiO2 < 200 mmHg • CXR: bilateral infiltrates雙側浸潤 • 排除心因性呼吸衰竭 PAWP < 18 mmHg, no clinical evidence of LA HTN

  4. 致病原因 • Direct injury • Pneumonia • Gastric aspiration • Drowning • Fat and amniotic fluid embolism • Pulmonary contusion • Alveolar hemorrhage • Toxic inhalation • Reperfusion • Indirect injury • Severe sepsis • Transfusions • Shock • Salicylate or narcotic overdose • Pancreatitis

  5. Differential Diagnosis • Left ventricular failure • Intravascular volume overload • Mitral stenosis • Veno-occlusive disease • Lymphangitic carcinoma • Interstitial and airway diseases • Hypersensitivity pneumonitis • Acute eosinophilic pneumonia • Bronchiolitis obliterans with organising pneumonia Lancet 2007; 369:1553-65

  6. Prognosis & Outcome • Predictive of death: advanced age, shock, hepatic failure • Overall 28-day mortality: 20-40% • Lung function: returns to normal over 6-12 months • Common complications: neuropsychiatric problems, neuromuscular weakness Lancet 2007; 369:1553-65

  7. Pathophysiology • Exudative phase • Cytokines  inflammation  surfactant dysfunction  atelectasis • Elastase epithelial barrier damage  edema • Procoagulant tendency  capillary thrombosis • Fibroproliferative phase • Chronic inflammation • Fibrosis • neovascularisation Lancet 2007; 369:1553-65

  8. NEJM 2000;342:1334-1349

  9. NEJM 2000;342:1334-1349

  10. NEJM 2000;342:1334-1349

  11. Treatment • No specific treatment • Mainstay of treatment: supportive care • Avoid iatrogenic complications • Treat the underlying cause • Maintain adequate oxygenation

  12. Supportive Care • Prevention of deep vein thrombosis, gastrointestinal bleeding, and pressure ulcers • Semi-recumbent position • Enteral nutrition • Infection control • Goal-directed sedation practice • Glucose control

  13. Ventilator Strategy

  14. Barotrauma Volutrauma Atelectrauma Biotrauma Ventilator-induced Lung Injury (VILI) Over Distension Collapse

  15. Volutrauma • Increased alveolar wall stress (stretch) by high tidal volume • Parenchymal injury • Gross physical disruption • Stretch-responsive inflammatory pathways AJRCCM 1998; 157: 294-323

  16. Lung edema PEEP PEEP PEEP Atelectrauma • Cyclic closing and reopening of alveoli • Alveolar shear stress-related injury • Heterogeneous nature of lung aeration in ALI/ARDS

  17. The PEEP Effect NEJM 2006;354:1839-1841

  18. Ventilator-induced Lung Injury (VILI) Upper Deflection point Lower Inflection point

  19. Lung-Protective Ventilation ARDS Network, 2000: Multicenter, randomized 861 patients NEJM 2000; 342: 1301-1308

  20. Lung-Protective Ventilation • Result: • Lower 22% mortality (31% vs 39.8%) • Increase ventilator-free days NEJM 2000; 342: 1301-1308

  21. Concerns when using lung-protective strategy… • Heterogeneous distribution • Hypercapnia • Auto-PEEP • Sedation and paralysis • Patient-ventilator dyssynchrony • Increased intrathoracic pressure • Maintenance of PEEP

  22. Other Ventilator Strategies • Lung recruitment maneuvers • Prone positioning • High-frequency oscillatory ventilation (HFOV)

  23. Lung Recruitment • To open the collapsed alveoli • A sustained inflation of the lungs to higher airway pressure and volumes • Ex.: PCV, Pi = 45 cmH2O, PEEP = 5 cmH2O, RR = 10 /min, I : E = 1:1, for 2 minutes NEJM 2007; 354: 1775-1786

  24. Lung Recruitment NEJM 2007; 354: 1775-1786

  25. Lung Recruitment NEJM 2007; 354: 1775-1786

  26. Lung Recruitment • Potentially recruitable (PEEP 5  15 cmH2O) • Increase in PaO2:FiO2 • Decrease in PaCO2 • Increase in compliance • The effect of PEEP correlates with the percentage of potentially recruitalbe lung • The percentage of recruitable lung correlates with the overall severity of lung injury Sensitivity : 71% Specificity : 59% NEJM 2007; 354: 1775-1786

  27. Lung Recruitment • The percentage of potentially recruitable lung: • Extremely variable, • Strongly associated with the response to PEEP • Not routinely recommended

  28. Prone Position

  29. Prone Position • Mechanisms to improve oxygenation: • Increase in end-expiratory lung volume • Better ventilation-perfusion matching • More efficient drainage of secretions

  30. Prone Position NEJM 2001;345:568-573

  31. Prone Position NEJM 2001;345:568-573

  32. Prone Position • Improve oxygenation in about 2/3 of all treated patients • No improvement on survival, time on ventilation, or time in ICU • Might be useful to treat refractory hypoxemia • Optimum timing or duration ? • Routine use is not recommended

  33. High-Frequency Oscillatory Ventilation (HFOV)

  34. HFOV Frequency: 180-600 breaths/min (3-10Hz)

  35. Effect of HFOV on gas exchange in ARDS patients AJRCCM 2002; 166:801-8

  36. Survival difference of ARDS patients treated with HFOV or CMV 30-day: P=0.057 90-day: P=0.078 AJRCCM 2002; 166:801-8

  37. HFOV • Complications: • Recognition of a pneumothorax • Desiccation of secretions • Sedation and paralysis • Lack of expiratory filter • Failed to show a mortality benefit • Combination with other interventions ? Chest 2007; 131:1907-1916

  38. Adjunctive Therapy • Steroid treatment • Fluid management • Extracorporeal membrane oxygenation (ECMO) • Nitric oxide • Others

  39. Steroid therapy NEJM 2006;354:1671-1684

  40. Steroid therapy • Increase the number of ventilator-free and shock-free days during the first 28 day • Improve oxygenation, compliance and blood pressure • No increase in the rate of infectious complications • Higher rate of neuromuscular weakness • Routine use of steroid is not supported • Starting steroid more than 14 days after the onset of ARDS may increase mortality NEJM 2006;354:1671-1684

  41. Fluid Management NEJM 2006;354:2564-2575

  42. Fluid Management NEJM 2006;354:2564-2575

  43. Fluid Management NEJM 2006;354:2213-24

  44. Fluid Management • Conservative strategy improves lung function and shortens the duration of ventilator use and ICU stay • No significant mortality benefit • The use of pulmonary artery catheter not routinely suggested

  45. Extracorporeal Membrane Oxygenation (ECMO) • No improvement on survival or time on ventilation • Substantial risk of infection and bleeding • Not routinely recommended

  46. Nitric Oxide • Vasodilator • Improve oxygenation and pulmonary vascular resistance • No improvement on survival • Routine use is not recommended

  47. Unproven Treatments • Ketoconazole • Pentoxyfilline and lisofylline • Nutritional modification • Antioxidants • Neutrophil elastase inhibition • Surfactant • Liquid ventilation Lancet 2007; 369:1553-65

  48. Conclusions • The only treatment that shows mortality benefit: • lung-protective ventilation strategy • Low tidal volume (6ml/Kg), high PEEP, adequate Pplat (<30 cmH2O) • Modalities to improve oxygenation: • Prone position, steroid, fluid treatment, steroid, HFOV, NO • Combining other treatments: • Activated protein C, antibiotics, EGDT…etc

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