Acute Respiratory Distress Syndrome (ARDS)

Berlin Criteria Definition (1)

  1. PaO2/FiO2 < 300 (0-100 = severe, 101-200 = moderate, 201-300 = mild) on PEEP of at least 5 mmHg.
  2. Radiographic evidence of non-cardiogenic pulmonary edema (see picture below)
  3. Acute onset within 1 week of known insult

Etiologies

  • Sepsis
  • Aspiration
  • Pneumonia (including COVID-19 or influenza)
  • Trauma
  • Transfusion-Related Acute Lung Injury (TRALI)
  • Stem cell transplantation
  • Pancreatitis
  • Drugs/Alcohol

Basic Management

  • Ventilator settings
    • Tidal Volume: 6 mL/kg ideal body weight (2)
      • This may induce hypercapnea and respiratory acidosis, which is allowed to a limit of pH of 7.3
    • FiO2: Start at 100% and wean down as able
    • RR: Will have to start higher (~30 rpm) to compensate for low tidal volume to maintain an adequate minute ventilation volume (MVV = VT x RR)
    • PEEP: Controversial, but the idea is to keep the stress index at 1 (keeping the pressure-time curve linear instead of convex or concave)
      • Concave (Stress index < 1) indicates pressure rising too quickly, consider increasing PEEP to help inflate lung
      • Convex (Stress index >1) indicates pressure rising too slowly, consider decreasing PEEP
  • Diuresis
    • Attempts to diurese to a goal of CVP < 4 mmHg as long as patient remains well-perfused
  • Paralyzation
    • Mechanism of benefit is unclear, but decreases mortality likely as a result of decreasing asynchrony on the ventilator (3)
  • Proning
    • With the patient prone, gas will move in a dependent fashion toward the posterior lung fields, which carry a greater surface area, allowing for improved gas exchange.
    • Typically reserved for an SpO2/FiO2 ratio < 180 or PaO2/FiO2 ratio < 150
  • ECMO (Extracorporeal Membrane Oxygenation)
    • Can be considered in individuals not improving with above therapies
  • Inhaled Nitric Oxide not shown to have mortality benefit (4)
  • Surfactant not shown to have mortality benefit (5)
  • Steroids not shown to have mortality benefit (6)

References

  1. Amin, Zulkifli, et al. “Benefit of the Application of New ARDS Criteria (Berlin) Compared to Old Criteria (AECC) in a Tertiary Hospital in a Developing Country.” Indian Journal of Public Health Research & Development, vol. 8, no. 2, 2017, p. 273., doi:10.5958/0976-5506.2017.00125.5.
  2. Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome. New England Journal of Medicine, 45(1), 19-20. doi:10.1097/00132586-200102000-00017
  3. Mclean, D., & Eikermann, M. (2018). Neuromuscular Blockers in Early Acute Respiratory Distress Syndrome. 50 Studies Every Intensivist Should Know, 123-128. doi:10.1093/med/9780190467654.003.0020
  4. Use of inhaled nitric oxide in patients with acute respiratory failure with low blood oxygen does not improve survival. (n.d.). Retrieved November 11, 2020, from https://www.cochrane.org/CD002787/EMERG_use-inhaled-nitric-oxide-patients-acute-respiratory-failure-low-blood-oxygen-does-not-improve
  5. Raghavendran, K., Willson, D., & Notter, R. (2011, July). Surfactant therapy for acute lung injury and acute respiratory distress syndrome. Retrieved November 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153076/
  6. Khilnani, G., & Hadda, V. (n.d.). Corticosteroids and ARDS: A review of treatment and prevention evidence. Retrieved November 11, 2020, from http://europepmc.org/articles/PMC3109833

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