pediatric ards: understanding it and managing it james d. fortenberry, md medical director,...
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Pediatric ARDS: Understanding It and
Managing It
Pediatric ARDS: Understanding It and
Managing ItJames D. Fortenberry, MD
Medical Director, Pediatric and Adult ECMO
Medical Director, Critical Care Medicine
Children’s Healthcare of Atlanta at Egleston
New and ImprovedNew and Improved
Adult Respiratory Distress Syndrome
Acute Respiratory Distress Syndrome
ARDS: New Definition
Criteria Acute onset Bilateral CXR infiltrates PA pressure < 18 mm Hg Classification
Acute lung injury - PaO2 : F1O2 < 300
Acute respiratory distress syndrome - PaO2 : F1O2 < 200
- 1994 American - European Consensus Conference
Clinical Disorders Associated with ARDS
Direct Lung Injury Indirect Lung Injury
Common causes Common Causes
Pneumonia SepsisAspiration of gastriccontents
Severe trauma with shock ,multiple transfusions
Less common causes Less common causes
Pulmonary contusion Cardiopulmonary bypassFat emboli Drug overdoseNear-Drowning Acute pancreatitisI nhalational injury Transfusions of blood productsReperfusion pulmonaryedema
The Problem: Lung Injury
Etiology In Children
Other 4%
Hemorrhage 5%
Trauma 5%
Noninfectious Pneumonia 14%
Cardiac Arrest 12%
Septic Syndrome 32%
Infectious Pneumonia 28%
Davis et al., J Peds 1993;123:35
ARDS - Pathogenesis
Instigation
• Endothelial injury: increased permeability of alveolar - capillary barrier
• Epithelial injury : alveolar flood, loss of surfactant, barrier vs. infection
• Proinflammatory mechanisms
ARDS Pathogenesis
Resolution
• Equally important
• Alveolar edema - resolved by active sodium transport
• Alveolar type II cells - re-epithelialize
• Neutrophil clearance needed
ARDS - Pathophysiology
•Decreased compliance
•Alveolar edema
•Heterogenous
•“Baby Lungs”
ARDS:CT Scan View
Phases of ARDS
• Acute - exudative, inflammatory
(0 - 3 days)
• Subacute - proliferative
(4 - 10 days)
• Chronic - fibrosing alveolitis
( > 10 days)
ARDS - Outcomes
• Most studies - mortality 40% to 60%; similar for children/adults
• Death is usually due to sepsis/MODS rather than primary respiratory
• Mortality may be decreasing
53/68 % 39/36 %
ARDS - Principles of Therapy
•Provide adequate gas exchange
•Avoid secondary injury
Therapies for ARDS
Innovations:NOPLVProningSurfactantAnti-Inflammatory
Mechanical Ventilation Gentle
ventilation:
Permissive hypercapnia
Low tidal volume
Open-lung
HFOV
ECMOIVOX
IV gas exchange
AVCO2R
Total Implantable Artificial Lung
ARDS
Extrapulmonary Gas Exchange
The Dangers of Overdistention
• Repetitive shear stress
• Injury to normal alveoli
• inflammatory response
• air trapping
• Phasic volume swings: volutrauma
• compliance
• intrapulmonary shunt
• FiO2
• WOB
• inflammatory response
The Dangers of Atelectasis
0
10
20
13 33 38
Airway Pressure (cmH20)
Lun
g V
olum
e (m
l/kg)
AtelectasisAtelectasis
““Sweet Sweet Spot”Spot”
OverdistentioOverdistentionn
Lung Injury Zones
ARDS: George Bush Therapy
“Kinder, gentler” forms of ventilation:
•Low tidal volumes (6-8 vs.10-15 cc/kg)
•“Open lung”: Higher PEEP, lower PIP
•Permissive hypercapnia: tolerate higher pCO2
Lower Tidal Volumes for ARDS
0
5
10
15
20
25
30
35
40
Percent
Death
Ven
t freed
ays
Traditional Lower
*
*
* p < .001
ARDS Network,NEJM, 342: 2000
22% decrease
Is turning the ARDS patient “prone” to be
helpful?
Is turning the ARDS patient “prone” to be
helpful?
Prone Positioning in ARDS
• Theory: let gravity improve matching perfusion to better ventilated areas
• Improvement immediate
• Uncertain effect on outcome
Prone Positioning in Pediatric ARDS:Longer May Be Better
• Compared 6-10 hrs PP vs. 18-24 hrs PP
• Overall ARDS survival 79% in 40 pts.
Relvas et al., Chest 2003
Brief vs. Prolonged Prone Positioning in Children
0
5
10
15
20
25
Pre- PP Brief PP Prolonged PP
Oxygen
ati
on
In
dex
(OI)
- Relvas et al., Chest 2003
*
***
High Frequency High Frequency Oscillation:Oscillation:A Whole Lotta A Whole Lotta Shakin’ Goin’ Shakin’ Goin’ OnOn
- Reese Clark- Reese Clark
It’s not absolute pressure, but volume or
pressure swings that promote lung injury or
atelectasis.
It’s not absolute pressure, but volume or
pressure swings that promote lung injury or
atelectasis.
•Rapid rate
•Low tidal volume
•Maintain open lung
•Minimal volume swings
High Frequency Ventilation
High Frequency Oscillatory Ventilation
HFOV is the easiest way to find the ventilation
“sweet spot”
HFOV: Benefits Vs. Conventional Ventilation
0
20
40
HFOV CV CV toHFOV
HFOV toCV
Sur
viva
l wit
h CL
D%
- - Arnold et al, Arnold et al, CCMCCM, , 19941994
**
HFOV vs. CMV in Pediatric Respiratory Failure
Surfactant in ARDS
• ARDS: surfactant deficiency surfactant present is
dysfunctional
• Surfactant replacement improves physiologic function
Surfactant in Pediatric ARDS
•Current randomized multi-center trial
•Placebo vs calf lung surfactant (Infasurf)
•Children’s at Egleston is a participating center-study closed, await results
Steroids in Unresolving ARDS
• Randomized, double-blind, placebo-controlled trial
• Adult ARDS ventilated for > 7 days without improvement
• Randomized: Placebo Methylprednisolone 2 mg/kg/day x 4
days, tapered over 1 month
Meduri et al, JAMA 280:159, 1998
Steroids in Unresolving ARDS
0102030405060708090
100
ICUsurvival
Hospitalsurvival
Steroid Placebo
* *
p<.01*- Meduri et al., JAMA, 1998
Steroids in Unresolving ARDS
• Randomized, double-blind, placebo-controlled trial
• ARDSNetwork-180 adults
• Randomized: Placebo Methylprednisolone No mortality difference Decreased ventilator-free days but
only if started 7-14 daysSteinberg, NEJM, 354:1671,2006
Inhaled Nitric Oxide in Respiratory Failure
Neonates Beneficial in term neonates with
PPHN Decreased need for ECMO
Adults/Pediatrics Benefits - lowers PA pressures,
improves gas exchange Randomized trials: No difference
in mortality or days of ventilation
Inhaled NO and HFOV In Pediatric ARDS
5853
58
71
0
10
20
30
40
50
60
70
80
Sur
viva
l %
Dobyns et al., Dobyns et al.,
J PedsJ Peds, 2000, 2000
*
Partial Liquid Ventilation
Partial Liquid Ventilation
Mechanisms of action oxygen reservoir recruitment of lung volume alveolar lavage redistribution of blood flow anti-inflammatory
Liquid Ventilation
Pediatric trials started in 1996 Partial: FRC (15 - 20 cc/kg)
Study halted 1999 due to lack of benefit
Adult study (2001): no effect on outcome
ARDS- “Mechanical” Therapies
ARDS- “Mechanical” Therapies
Prone positioning - Unproven outcome benefit
Low tidal volumes - Outcome benefit in large study
Open-lung strategy - Outcome benefit in small study
HFOV -Outcome benefit in small study
ECMO - Proven in neonates unproven in children
Pharmacologic Approaches to ARDS: Randomized Trials
Glucocorticoids
Fibrosing alveolitis - lowered mortality, small study
Surfactant - possible benefit in children
Inhaled NO - no benefit
Partial liquid ventilation - no benefit
“…We must discard the old approach and continue to search for ways to improve mechanical ventilation. In the meantime, there is no substitute for the clinician standing by the ventilator…”
- Martin J. Tobin, MD