What is the pathogenesis of sepsis-induced ARDS in sepsis/septic shock?

Updated: Oct 07, 2020
  • Author: Andre Kalil, MD, MPH; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

The pathogenesis of sepsis-induced ARDS is a pulmonary manifestation of SIRS. A complex interaction between humoral and cellular mediators, inflammatory cytokines and chemokines, is involved in this process. A direct or indirect injury to the endothelial and epithelial cells of the lung increases alveolar capillary permeability, causing ensuing alveolar edema. The edema fluid is protein-rich; the ratio of alveolar fluid edema to plasma is 0.75-1.0, whereas in patients with hydrostatic cardiogenic pulmonary edema, the ratio is less than 0.65.

Injury to type II pneumocytes decreases surfactant production; furthermore, the plasma proteins in alveolar fluid inactivate the surfactant previously manufactured. These enhance the surface tension at the air-fluid interfaces, producing diffuse microatelectasis.

Neutrophil entrapment within the pulmonary microcirculation initiates and amplifies the injury to alveolar capillary membrane. ARDS is a frequent manifestation of these effects.


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