ARDS Flashcards

1
Q

What is Acute Respiratory Distress Syndrome?

A

acute diffuse inflammatory lung injury leading to increase pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue

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2
Q

What is the Berlin 2012 criteria for ARDS?

A
  • ACUTE: Symptom onset within 1 week of known clinical insult
  • Pulmonary Edema: Bilateral opacities consistent with pulmonary edema
  • Respiratory failure not fully explained by fluid overload or cardiac failure (may use echo to exclude)
  • Hypoxemia: Ratio of arterial oxygen tension to fraction inspired oxygen is <300mmHg
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3
Q

What is mild ARDS?

A

PaO2/FiO2 200-300mmHg on ventilatory setting with PEEP> 5cmH20

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4
Q

What is moderate ARDS

A

PaO2 /FiO2 100-200mmHg with ventilator settings of PEEP 5cmH2O

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5
Q

What is severe ARDS?

A

PaO2/FiO2 < 100mmHg on ventilator settings including PEEP > 5 cm H20

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6
Q

What are the causes of ARDS?

A
  • Direct
    • infection
    • Contusion from blunt trauma
    • Aspiration
    • Smoke inhalation
    • Near drowning
  • Indirect (non-pulmonary)
    • Sepsis
    • Major trauma
    • Prolonged hemorrhage
    • Embolism (fat/amniotic fluid/thrombotic)
    • Burns
    • Pancreatitis
    • DIC
    • Massive blood transfusion
    • Cardiopulmonary bypass
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7
Q

What are the phases of ARDS?

A
  • Injury
  • Exudative
  • Proliferative
  • Fibrotic
  • Resolution
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8
Q

What are the phases of ARDS?

A
  • Injury
  • Exudative
  • Proliferative
  • Fibrotic
  • Resolution
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9
Q

Describe the immediate exudative phase of ARDS.

A
  • capillary endothelial injury and alveolar epithelial injury mediated by cytokines
  • Increase permeability leading to widespread pulmonary edema + alveolar collapse
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10
Q

Describe proliferative phase of ARDS.

A

Proliferation and activation of type 2 pneumocytes and fibroblasts

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11
Q

Describe the fibrotic phase of ARDS.

A

Infiltration of fibroblasts, replacing alveoli and alveolar ducts with fibrosis

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12
Q

Effects of ARDS pathophysiology on respiratory function

A
  • Hypoxemia
  • Lung collapse and consolidation
  • Decreased compliance
  • Increased minute ventilation
  • Increased work of breathing
  • Pulmonary hypertension
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13
Q

Management of ARDS

A
  • Treat precipitating condition
  • Nutritional support
  • Strict fluid management (sedation + diuresis if stable)
  • Prophylaxis for stress ulcer
  • Prevention of nosocomial pneumonia
  • Ventilation strategy
  • Muscle relaxant
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14
Q

What are the mechanical ventilation strategies for ARDS?

A
  • Post- ARMA lung protective ventilation protocol:
  • Low tidal volume 6ml/kg (predicted body weight)
  • Permissive hypercapnia
  • Pplat < 30 cm H20
  • High PEEP 10-20cmH2O
  • Inverse ratio ventilation
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15
Q

What did the ARMA trial conclude?

A
  • MC RCT
  • Traditional TV. 12ml /kg vs low TV 6ml/kg
  • Outcome:
    • less in-hospital mortality
    • significant reduction in duration of MV
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16
Q

What are the salvage therapies for refractory ARDS?

A

Prone positioning

Neuromuscular blockade

Recruitment manoeuvres

Unconventional ventilator modes (Airway Pressure Release Ventilation, High frequency oscillatory ventilation)

17
Q

What is prone positioning beneficial?

A

Recruit collapsed dorsal alveolar to improve V/Q mismatch

18
Q

What are complications of prone positioning?

A
  • Pressure ulcers
  • Airway obstruction
  • Increase abdominal pressure with liver/renal dysfunction
  • Loss of venous access
  • Dislodgement of endotracheal tube
19
Q

Contraindications to prone positioning

A
  • Severe facial / neck trauma
  • Elevated ICP
  • Pelvic/spinal instability
  • High probability of CPR
20
Q

What are the benefits of neuromuscular blocking agents?

A

Abolish patient’s inspiratory and expiratory efforts to improve patient-ventilatory synchrony

Minimize muscle oxygen consumption

21
Q

What is a recruitment manoeuvre?

A

Transient sustained increase transpulmonary pressure to attempt to open previously collapsed alveoli

22
Q

What are some methods of recruitment manoeuvres?

A
  • CPAP mode: applied pressure of 30-40cmH20 for 30-40 seconds
  • Stepwise: incremental PEEP with constant driving pressure
23
Q

Pharmacological therapies for ARDS

A
  • Surfactant therapy
  • Inhaled vasodilators (NO, prostacyclins)
  • Steroids
24
Q

What is high frequency oscillatory ventilation?

A
  • low tidal volume (1-4ml/kg)
  • high RR and mean airway pressure (3-15 Hz)
    *
25
Q

What does evidence say about HFOV?

A

OSCILLATE trial 2013 and

  • Conclusion:
    • no mortality benefit
    • recent trial showing increased mortality in mild-moderate ARDS but survival benefit for very severe ARDS
26
Q

What are the clinical features of ARDS?

A
  • Dyspnea
  • Tachypnea
  • Hypoxia refractory to oxygen therapy
  • Crepitations on auscultations of chest
  • New bilateral diffuse infiltrates on CXR