ARDS Flashcards
What are the two types of pulmonary edema?
Hydrostatic pulmonary edema: increased hydrostatic capillary pressure, usually cardiac causes or volume expansion
Permeability pulmonary edema: increased permeability of the alveolar capillary membrane; this is what happens in ARDS
What’s the difference bewteen the two types of pulmonary edema?
Which type of pulmonary edema do we see in ARDS?
Permeability pulmonary edema
What is the pathophysiology of ARDS?
Acute injury to the alveolus –> increased permeability between capillary/alveolar barrier –> airspaces will fill with fluid and cellular debris
This edema –> neutrophils enter the airspaces, macrophages too
What do the lungs from ARDS look like in gross pathology?
Heavy, firm, airless, “beefy,” bright red
What are the 2 pathologic stages of ARDS?
Exudative: edema, hyaline membrane proliferation
Proliferative: fibroblast and myofibroblast proliferation
What is the Berlin definition of ARDS?
PaO2/FiO2 ratio < 300 9 (with PEEP at least 5 cm)
Respiratory symptoms began within 1 week of a known insult
Bilateral opacities consistent wtih pulmonary edema on CT or CXR
Clinical picture not fully explained by cardiac failure or fluid overload (do an echo)
Who is at higher risk of getting ARDS?
Alcohol abuse
Poor nutritional status
Advanced age
Greater severity of illness
Cirrhosis
What causes ARDS?
Direct lung injury: pneumonia, aspiration, near drowning, toxic inhalation, trauma (bruising, fat emboli), reperfusion injury
Indirect injury/inflammation: non-pulmonary sepsis, pancreatitis, ingestions/medications, transfusion-related lung injury, massive trauma/burns, cardiac bypass, amniotic fluid embolism, neurogenic
What is the staging system for ARDS?
Based on P:F ratio
Mild: <300
Moderate: <200
Severe: <100
Correlates wtih mortality
What are the most common causes of death in ARDS – both early/late?
Early: underlying illness/injury
Late: multi-organ failure
Small % die from hypoxemia
What’s the long term outcome for survivors of ARDS?
Return of pulmonary function but persistent physical and psychological impairments
What is the clinical presentation of a patient with ARDS?
Tachypnea, tachycardia, cyanosis, crackles, bronchial breath sounds with consolidation, decreased breath sounds with pleural effusions
What are the consequences of ARDS?
How do you manage ARDS?
Mechanical ventilation: low tidal volume, PEEP, salvage ventilatory strategies
Fluid management: dry lung is a happy lung
What are salvage strategies that might work in severe ARDS?
Pulmonary vasodilators (inhaled NO, epoprostenol)
Prone positioning
High frequency oscillatory ventilation
ECMO
What is ECMO?
Extracorporeal membrane oxygenation
Neg pressure pulls venous blood into a pump
Blood gets spun and oxygenated = O2 in, CO2 out
Oxygenated blood goes back into either a vein or an artery
When is ECMO used?
Hypoxemic respiratory failure
Hypercapnic respiratory failure
Bridge to lung & heart transplantation
Pulmonary hypertension
Massive pulmonary embolism
Severe broncho-pleural fistulas
Failure to wean from cardiopulmonary bypass in the OR
Heart failure
eCPR
What are the indications for ECMO in ARDS?
Indications: severe hypoxemia (P:F <80)
uncompensated hypercapnia with acidemia (pH<7.15)
High end inspiratory pressure >35 cm H2O (siff lungs)
Contraindications: high pressure ventilation for >7 days
High FiO2 requirements for >7 days
Limited vascular access
Any dysfunction that limits its benefit of ECMO i.e. coma
Absolute contraindication:
Any condition that precludes the use of anticoagulation therapy
What is ECCO2R?
ECMO + artificial removal of CO2
Permits lung-protective ventilation, low tidal volume
Has other implications besides ARDS i.e. bridge to lung transplant
What’s the benefit of not using a ventilator?
No VAP = vent associated pneumonia
No VALI (vent assoc. lung inj) or oxygen toxicity
Ambulation
Increased pt comfort
Decreased need for sedation
Oral nutrition
