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21 Cards in this Set
- Front
- Back
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Define ARDS
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Acute onset of dyspnea, bilateral infiltrates on CXR or CT, hypoxemia, absence of heart failure and presence of an inappropriate trigger.
Tends to occur in posterior parts of the lung while people lay supine |
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How do you measure hypoxemia
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The P/F ratio. It is normally PaO2 over .21. It comes out to about 450. Falling below 300 is called acute lung injury. Falling below 200 is ARDS
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How do you know it is ARDS and not CHF which is the most common cause of bilateral infiltrates?
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A low PCWP suggests ARDS. We usually just do an echocardiography to check.
CHF responds to diuretics while ARDS does not |
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What triggers ARDS?
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Direct injury: Aspiration, inhalation, infection, lung contusion, near drowning, fat/amniotic emboli, reperfusion
Indirect injury: Sepsis, severe non-thoracic trauma, blood transfusion, cardiopulmonary bypass, drug overdose, pancreatitis Near drowning Indirect is usually worse. Sepsis is the worst |
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Hyaline membranes
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Pathognomonic lesion for ARDS
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Pathophysiology of ARDS
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Alveolar injury -> Flooding ->hyaline membranes -> Type I necrosis -> Hyperplasia of Type II -> Fibrosis
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Describe the timeframe of ARDS
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Edema in the first few days, development of hyaline membranes, inflammatory filtrate follows, and then fibrosis
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What is the primary problem during the non-cardiogenic pulmonary edema phase of ARDS
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Shunt physiology creates hypoxemia
Oxygen improves as edema resolves When there people devolop interstitial thickening and fibrosis, the problem is ventilation/dead space |
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What does the lung look like following injury
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There is diffuse alveolar damage which is associated with hyaline membranes.
DAD is not necessary for diagnosis of ARDS but it is pathognomonic for ARDS |
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Grossly what do DAD lungs look like?
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They are heavy, full of blood, inflammatory cells, and protein?
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Low vs High fluid management of ARDS
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No difference in mortality but can get them out of ICU faster with low fluids. There is no association of low fluid strategy with more organ failures.
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What if you use nitric oxide to treat ARDS?
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It goes to well ventilated parts of lungs and dilates the pulmonary vasculature. Gas exchange improves and pulmonary artery pressure drops. It may have antiinflammatory effects.
When you go off of it, pulmonary htn rebounds. It is expensive. It does not improve survival rates Rescue therapy only |
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What if you treat ARDS with corticosteroids?
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May be harmful in acute phase.
No difference in 60-day mortality. May reduce ventilatory days, ICU days, and reduce incidence of shock in the first month after injury Complications were polyneuropathy and neuromuscular disease May be high risk of death if you wait till after day 14 to start them. So, there may be a window from 7-13 days when steroids are beneficial |
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What is the main strategy to deal with ARDS?
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mechanical ventilation
-Don't use negative pressure like with polio -Noninvasive positive pressure doesnt have high enough fraction of oxygen or enough pressure -We use invasive positive pressure. Disadavantages are it is easy to catch an infection, and it is uncomfortable |
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PEEP?
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Positive end expiratory pressure. Keeps alveoli from collapsing
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What about compliance in ARDS?
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Very low. You need high pressure air to get ventilation. Can lead to pneumothorax
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What are the main complications of mechanical ventilation in ARDS
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-Infection
-Hypotension -Barotrauma is pressure trauma -Sinusitis can develop. -Ventilation prevents adequate sinus drainage so it can be aspirated. -Pneumonia -Ventilator-induced lung injury |
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Should you use high tidal volumes and pressure or not?
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No because you can damage the lungs. It may release cytokines and inflammatory mediators. Can generate DAD. So you should probably tolerate poor gas exchange.
Low tidal volumes improves survival |
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Does the trigger matter in ARDS
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Yes, direct is better than indirect. Trauma is best, sepsis is worst.
Mortality for ARDS is not predicted by initial gas exchange |
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what causes death with ARDS
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1. Sepsis and progressive multi-organ failure
2. Respiratory causes |
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What pulmonary function is most likely to remain impaired in those surviving ARDS
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CO diffusing capacity
Remember, most survivors have major problems in all areas of life afterwards |
