ARDS Flashcards
According to the berlin definition, what is the timing parameter needed to consider ARDS?
The respiratory conditions associated with ARDS must manifest within 1 week of a known clinical event
What imaging results are associated with ARDS?
Bilateral opacities similar to pulmonary edema appear on CXR or CT scan
What specific distinction must we be able to make about the bilateral opacities in order to support a diagnosis of ARDS?
The opacities cannot fully be explained by pleural effusion, lobar or lung collapse or pulmonary nodules
The edema cannot have a cardiogenic source
How can you rule out a cardiogenic source when considering ARDS?
Cxr to look at the cardiac silhouette
Echocardiogram
How is the severity of ARDS determined?
The P/F ratio
Mild ARDS would be characterized by a P/F ratio of what?
201-300
Moderate ARDS would be characterized by a P/F ratio of what?
101-200
Severe ARDS would be characterized by a P/F ratio of what?
Less than 100
What is the Frank Starling Law and what does it describe?
It describes net fluid movement out of a capillary based on capillary and interstitial hydrostatic and oncotic pressure
What portion of the frank starling law does congestive heart failure affect?
In congestive heart failure, capillary hydrostatic pressure is increased which results in more fluid being pushed out of the capillaries and into the interstitium
Describe the fluid produced in CHF
Transudate
Thin, watery fluid that is protein poor
Describe the fluid found in non-cardiogenic pulmonary edema
Exudate
Protein rich
Macrophages, neutrophils
What can happen if a pleural effusion is drained too rapidly?
Decompression pulmonary edema
Fluid leaving the space creates a negative pressure area which can pull fluid out of the capillaries and into the alveoli
What can cause a decrease in intrapleural pressure?
Someone with an upper airway restriction gasping for breath can drive pressure down enough to cause a fluid shift
This is known as a self induced lung injury
Describe how altitude can cause a pulmonary edema
Forceful breathing at higher altitudes due to not being acclimated can cause a fluid shift into the alveoli due to the individual generating such a large negative pressure by breathing very forcibly
What can cause a decrease in capillary oncotic pressure?
Overtransfusion
Uremia = elevated urea concentration in blood
Malnutrition aka hypoproteinemia
Acute nephritis = inflammatory kidney disease
Polyarteritis nodosa = necrotic inflammation of blood vessels
Describe how ARDS is different from cardiogenic edema
Capillary permeability caused by ARDS results in alveoli being filled with exudate
A patient with ARDS can have no cardiogenic issues associated with the pulmonary edema
ARDS significantly impacts oxygenation and is resistant to treatment with CPAP
What are some additional conditions/behaviors that can cause pulmonary edema?
Allergic reaction to drugs
Excessive sodium consumption
Drug overdose
Metal poisoning
Chronic alcohol ingestion
Aspiration
What is the most common cause of ARDS?
Sepsis
Why does sepsis frequently result in ARDS?
Sepsis is a dysregulated host response to an infection. As part of the inflammatory process, excessive capillary permeability can result in the alveoli being flooded with fluid and lymphocytes that can attack the alveoli directly resulting in more inflammation and damage
What criteria must be met in order to diagnose sepsis?
Temp >38.3 or < 36
HR > 90 bpm
RR > 20 or PaCO2 < 32 mmHg
WBC > 12000 or >10% Bands
And a sepsis induced organ dysfunction
Give some examples of sepsis induced organ dysfunction?
Hypotension
Lactate > 2 mmol (evidence of anaerobic metabolism)
Creatinine > 2.0 mg/dL
Total bilirubin > 2.0 mg/dL
Platelets < 100k per microliter
Coagulopathy
Encephalopathy
Acute respiratory failure