pediatric acute respiratory distress syndrome
TRANSCRIPT
Pediatric Acute Respiratory Distress Syndrome
Dr. Mohammad AvaisUPRIMS&R Saifai
Bismillahirehmaniraheem
ARDS: Old Definition
Criteria:1. Acute onset (<7 days)2. Bilateral CXR infiltrates3. Absence of left atrial hypertension • PAWP pressure < 18 mm Hg.
4. Severe hypoxemiaa) Acute lung injury - PaO2 : F1O2 < 300b) Acute respiratory distress syndrome - PaO2 : F1O2 < 200
1994 American – European Consensus Conference
Adult Respiratory Distress Syndrome Acute Respiratory Distress Syndrome
Berlin Definition of ARDS 2012
The significant changes in New Berlin definitions:Improvement:a)The ALI category was eliminated and replaced with a gradation of ARDS severity (mild, moderate, and severe) based on the degree of oxygenation disturbance.
b)A minimum of 5 cm of water positive end-expiratory pressure (PEEP) was required.
c)The determination of cardiac failure was rendered more subjective in view of the decreased utilization of pulmonary artery catheters.
Limitations:a)Necessity of invasive measurement of arterial oxygen.
b)The PaO2/FIO2 (P/F) ratio is influenced by ventilator pressures (4–7).
c)The differences in risk factors, aetiology, pathophysiology, and outcomes between adults and children were not considered
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Pediatric Critical Care Medicine 2015
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• Oxygenation Index = (FIO2 × mean airway pressure × 100)/PaO2.
• Oxygenation Saturation Index = (FIO2 × mean airway pressure × 100)/SpO2.
When To Suspect ARDS
Causing Direct Injury • Pneumonia• Gastric aspiration• Less Common
• Pulmonary contusion• Fat emboli• Near drowning• Inhalational injury
Causing Indirect Injury• Sepsis• Shock after severe trauma• Less Common
• Cardiopulmonary bypass• Drug overdose• Acute pancreatitis• Massive blood
transfusions
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+ persistent hypoxemia refractory to oxygen
ARDS - Pathogenesis
Intensive Care Medicine, 2005
Pulmonary Edema
Breakdown of barriers
Lymphatic movement
ALVEOLAR EDEMA
Alveolar lumen
FULL of fluid
Interstitial fluid
Pulmonary capillary
NORMAL ALVEOLI
Alveolar lumen
EMPTY of fluid
Pulmonary capillary
Protein
Phases of ARDS
•Acute - exudative, inflammatory(0 - 3 days)
• Subacute - proliferative (4 - 10 days)
• Chronic - fibrosing alveolitis( > 10 days)
Diagnosis
• Pulse oximetry• Arterial Blood Gas.• Capnography (end-tidal CO2 measurement)• A-aO2 gradient: Calculated by subtracting arterial
Po2 from alveolar. For the comparison to be valid, it must be at the same Fio2.
NELSON 19TH EDITION
MANAGEMENT•Control of causative factor• Infection- early antibiotic therapy.• Shock- intravascular volume expansion with crystalloids and
vasopressors.
•Careful fluid administration• Goal-directed fluid management.
•Analgesia and sedation.•Nutrition.• Blood Transfusion.• Psychosocial support.
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Oxygen Administration
•Nasal cannula• Flow rate <5 L/min.• FIO2 = 21%+ (nasal cannula flow (L min) × 3)
• Simple mask• Flow rate 5 to 10 L/min.
•Venturi mask• Adapter can be chosen to provide between 30 and
50% oxygen.• Flow rates of 5-10 L/min
•Airway Adjuncts.• Oropharyngeal Airway.• Nasopharyngeal airway, or Nasal trumpet.
•Positive Pressure Respiratory Support.• High-flow nasal cannula delivers gas flow at 4-16 L/min.• Bi-level positive airway pressure (BiPAP)
•Mechanical ventilation• Controlled oxygen exposure (FiO2)• Avoidance of volutrauma (low VT) and atelectrauma
(appropriate PEEP)
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•Non-conventional ventilation• High frequency ventilation• Liquid ventilation
•Drug-based therapies• Nitric oxide• Surfactant• Corticosteroids and other anti-inflammatory agents
• Positioning (Prone ventilation)
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Ventilation strategies
•Controlled Oxygen Exposure (FiO2)• PaO2 target is 55 to 80 mm Hg (SpO2 target 88%-95%).• Decrease FiO2 below 0.6 as soon as possible.
• Permissive Hypercapnia• Target arterial pH levels - 7.30 to 7.45.
•Mode of Ventilation • Time-cycled, pressure regulated, volume controlled mode.
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Kinder, gentler” forms of ventilation
“Open lung” Higher PEEP, lower PIP
Ventilator Goals
• Predicted body weight should be used, based on calculation
from gender and from height or length or from ulna length.
• Set the PEEP slightly higher than the lower inflection point
• Lower tidal volume (generally < 6 mL/kg)
• Static peak pressure <40 cm H20
• Wean oxygen to <60%
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• Tidal Volume (VT)• Patient-specific tidal volumes according to disease severity.• VT 3–6 mL/Kg of predicted body weight and plateau pressure 28 cmH2O.• In pressure controlled mode, VT should be accurately monitored.
• Positive End-Respiratory Pressure (PEEP)• Moderately elevated levels of PEEP (10–15 cm H2O) titrated to the
observed oxygenation and hemodynamic response in patients with severe ARDS.
• In absence of routine static PV curve measurement PEEP is increased by 2–3 cm H2O increments to maintain saturation between 90-95% with FiO2<0.6.
• If PV loops monitoring are available, then it is desirable to keep the PEEP above the lower inflection point.
• markers of oxygen delivery, respiratory system compliance, and hemodynamics should be closely monitored as PEEP is increased.
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• Inspiratory Time• The I:E ratio may be increased to 1:1 or 2:1 (inverse ratio ventilation) to
improve oxygenation.
• The exhaled tidal volume should be continuously monitored to prevent injurious ventilation and monitoring of ventilatory inspiratory pressure is important to prevent ventilator-induced lung injury.• At least daily assessment of predefined clinical and
physiologic criteria of extubation readiness in order to avoid unnecessary prolonged ventilation.
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•Weaning• In volume-controlled ventilation, the VT is usually reduced to
about 4–6 ml/kg. • In pressure-controlled ventilation, the PIP is gradually
reduced in steps of 1–2 cm H2O. • PEEP and FiO2 are reduced while monitoring the PaO2.
• Extubation• FiO2 of less than 40%, PEEP of 4–5 cm H2O, rate of 15/min
or less, PIP of less than 15 cm H2O; the child is hemodynamically stable and sensorium is normal/near normal with presence of protective reflexes.• Expert clinical judgment is best for extubation.
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Lung Injury Zones
0
10
20
13 33 38Airway Pressure (cmH20)
Lung
Vol
ume (
ml/k
g)
Atelectasis
“Sweet Spot”
Overdistention
Dangers
The Dangers of Over distention
• Repetitive shear stressa) Inflammatory Response
b) Air Trapping
• Phasic volume swings: volutrauma
• Injury to normal alveoli
The Dangers of Atelectasis
Compliance
Intrapulmonary shunt
FiO2
WOB
Inflammatory response
Indications for HFOV
• High-frequency oscillatory ventilation uses high-frequency very-low tidal volumes and laminar air flow to protect the lung and maintain open lung at minimal volume swings
• Severe persistent air leak- pneumothorax, bronchopleural fistulae
• Neonatal: HMD (*)
Pneumonia
Meconium aspiration
Lung hypoplasia
• Secretion-induced lung collapse
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It’s not absolute pressure, but volume or pressure swings that promote lung injury or atelectasis. - Reese Clark
Differences Between CMV and HFOV
CMV
HFV
Rate (BPM) Tidal volume (cc/kg) Alveolar pressure swings (cmH20) End exp. lung volume
0-120 4-20 5-50
low
120-1200 0.1-5 0.1-5
high
HFOV is the easiest way to find the ventilation “sweet spot”
Is turning the patient “prone” helpful?
no significant benefit of prone positioning (20 hrs./day for 7 days)
Permissive Hypercapnia
• Presence of hypercapnia in the setting of a mechanically ventilated
patient receiving limited inspiratory pressures and reduced tidal
volumes• Permissive hypercapnia should be considered for moderate-to-severe
PARDS to minimize ventilator-induced lung injury and maintaining pH 7.15–7.30 within lung protective strategy
• Exceptions to permissive hypercapnia should include intracranial hypertension, severe pulmonary hypertension, selected congenital heart disease lesions, hemodynamic instability and significant ventricular dysfunction.
www.pccmjournal.org
Pediatric ECMO
• Potential candidates•Neonate - 18 years• Reversible disease process• Severe respiratory/cardiac failure• < 10 days mechanical ventilation•Acute, life-threatening deterioration
ECMO
Pneumonia, sepsis, drowning, trauma,blood transfusion, pancreatitis, drugoverdose, DIC, burns
1. Acute onset2. Severe hypoxemia (PaO 2/FiO2 ratio
200 for ARDS and 300 for ALI)3. Bilateral pulmonary infiltrate4. No evidence of left atrial hypertension
Child with respiratory distress
Clinical assessment, pulse oximetry, CXR and ABG
Confirm diagnosis of ALI/ARDS
Identify underlying risk factors
Management
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Non-respiratory management
Respiratory management
Management
1. Intravascular volume resuscitation & inotropes
2. Blood transfusion3. Corticosteroids4. Nutrition5. Analgesia, sedation
Control of underlyingcause if possible e.g.antibiotics for sepsisand pneumonia
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Respiratory Management in Pediatric ARDS
Non-conventional ventilation
stable monitorEvaluation for Respiratory failure
Respiratory failure
Ventilatory support
Conventional ventilation
•PRVC mode•VT <6 ml/Kg•PEEP above the lower inflection point•Recruitment maneuvers•FiO2 below 0.6•Peak inspiratory pressure < 30 cm H2O
HFOV, CPAP
Target•PaO2 of 60 to 80 mm Hg•pH of 7.30 to 7.45
a) Prone positioningb) High frequency ventilationc) Surfactantd) Inhaled NO, prostacycline) ECMO
FAILURE
Stable
MonitorWean and extubateIndian J Pediatr (2010) 77:1296–1302
Berlin ARDS Taskforce 2012
ARDS- “Mechanical” Therapies
no benefit
Low tidal volumes Outcome benefit in large study
Prone positioning Unproven outcome benefit
Open-lung strategy Outcome benefit in small study
HFOV Outcome benefit in small study
ECMO Proven in neonates Unproven in children
SteroidAcuteFibrosing Alveolitis
No benefitLowered mortality, small study
Surfactant possible benefit in children
Inhaled NOPLV
No benefitNo benefit
Outcome
• Average mortality in children with an oxygenation index ≥13 at study entry was 36% vs. 20% in those with an oxygenation index ≤12.
Indian J Pediatr (2010) 77:1296–1302
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