Lec 14 ARDS Flashcards
What characterizes ARDS?
- PaO2/FiO2 < 200
- hypoxemia
- bilateral lung infiltrates
- no left atrial HTN
What characterizes acute lung injury [ALI]?
Pao2/FIO@ < 300
less severe hypoxemia
What is most important cause of ARDS?
sepsis
What are some things that cause ARDS?
sepsis pneumonia aspiration pancreatitis trauma burn trasnfusion
What is incidence of acute lung injury? ARDS?
acute lung injury = 80 / 10,000
ARDS = 59 / 10,000
What do you see on pathology in ARDS?
diffuse alveolar damage [DAD}
failure of alveolar capillary membrane and flooding of alveolar airspaces with proteinaceous fluid
oxygen derived free radicals cause microvascular injury and multi-organ failure
What inflammatory cytokines involved in development of ARDS?
TNF-alpha
IL-1
IL-8
What happens to surfactant in ARDS?
have depletion of surfactant –> atelectasis, gas exchange disturbance and decreased pulmonary compliance
What happens to microcirculation in ARDS?
altered NO and cytokine induced activation of coagulation cascade
What happens to fibroblasts in late phase ARDS?
fibroblasts proliferate
What is VILI?
ventilator induced lung injury = caused by us; we give positive airways pressure ventilation
since ARDS is patchy –> there are patches of normal lung that get injured by the ventilation
cause barotrauma and volutrauma –> cytokines released
What is history of ARDS?
edema phase = 1st 2 days –> alveolar capillary basement membrane broken down; proteinacious fluid exudes into alveolar space
hyaline membranes organizing = starts day 2; peaks day 4 and declines by day 7
fibroblast proliferation = starts day 7 –> leads to interstitial fibrosis
What is exudative vs proliferative phase of ARDS?
exudative = 1st week; have edema + hyaline membranes
proliferative = 2nd week; have interstitial inflammation + fibrosis due to fibroblast proliferation
What is triad for ARDS diagnosis?
bilateral lung infiltration
hypoxemia
no LA hypertension
What does imaging tell you in ARDS?
- necessary for diagnosis to see bilateral lung infiltrate
- tells you nothing about the stage
