ARDS

Question 1

What are the two types of pulmonary edema?

Answer 1

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

Question 2

What’s the difference bewteen the two types of pulmonary edema?

Answer 2

Question 3

Which type of pulmonary edema do we see in ARDS?

Answer 3

Permeability pulmonary edema

Question 4

What is the pathophysiology of ARDS?

Answer 4

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

Question 5

What do the lungs from ARDS look like in gross pathology?

Answer 5

Heavy, firm, airless, “beefy,” bright red

Question 6

What are the 2 pathologic stages of ARDS?

Answer 6

Exudative: edema, hyaline membrane proliferation

Proliferative: fibroblast and myofibroblast proliferation

Question 7

What is the Berlin definition of ARDS?

Answer 7

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)

Question 8

Who is at higher risk of getting ARDS?

Answer 8

Alcohol abuse

Poor nutritional status

Advanced age

Greater severity of illness

Cirrhosis

Question 9

What causes ARDS?

Answer 9

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

Question 10

What is the staging system for ARDS?

Answer 10

Based on P:F ratio

Mild: <300

Moderate: <200

Severe: <100

Correlates wtih mortality

Question 11

What are the most common causes of death in ARDS – both early/late?

Answer 11

Early: underlying illness/injury

Late: multi-organ failure

Small % die from hypoxemia

Question 12

What’s the long term outcome for survivors of ARDS?

Answer 12

Return of pulmonary function but persistent physical and psychological impairments

Question 13

What is the clinical presentation of a patient with ARDS?

Answer 13

Tachypnea, tachycardia, cyanosis, crackles, bronchial breath sounds with consolidation, decreased breath sounds with pleural effusions

Question 14

What are the consequences of ARDS?

Question 15

How do you manage ARDS?

Answer 15

Mechanical ventilation: low tidal volume, PEEP, salvage ventilatory strategies

Fluid management: dry lung is a happy lung

Question 16

What are salvage strategies that might work in severe ARDS?

Answer 16

Pulmonary vasodilators (inhaled NO, epoprostenol)

Prone positioning

High frequency oscillatory ventilation

ECMO

Question 17

What is ECMO?

Answer 17

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

Question 18

When is ECMO used?

Answer 18

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

Question 19

What are the indications for ECMO in ARDS?

Answer 19

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

Question 20

What is ECCO₂R?

Answer 20

ECMO + artificial removal of CO2

Permits lung-protective ventilation, low tidal volume

Has other implications besides ARDS i.e. bridge to lung transplant

Question 21

What’s the benefit of not using a ventilator?

Answer 21

No VAP = vent associated pneumonia

No VALI (vent assoc. lung inj) or oxygen toxicity

Ambulation

Increased pt comfort

Decreased need for sedation

Oral nutrition