Overview
Definition:
Pediatric Acute Respiratory Distress Syndrome (ARDS) is a life-threatening condition characterized by diffuse lung inflammation and acute respiratory failure
It is defined by the presence of acute onset hypoxemia (PaO2/FiO2 ratio < 300 mmHg, or in infants, lower thresholds based on age and lung injury), bilateral pulmonary infiltrates on chest imaging consistent with edema, and a non-cardiogenic cause of pulmonary edema.
Epidemiology:
The incidence of pediatric ARDS varies significantly by study and definition used, ranging from 1 to 4 per 100,000 children annually
Sepsis and pneumonia are the most common underlying causes in children, unlike in adults where pneumonia is also primary but other causes like aspiration are more prevalent
Mortality rates remain high, around 20-40%, though improvements in supportive care, including lung-protective ventilation and judicious fluid management, have led to some decline.
Clinical Significance:
Pediatric ARDS is a critical medical emergency requiring prompt recognition and management
Inadequate or excessive fluid administration can exacerbate lung injury, leading to worsening hypoxemia, prolonged mechanical ventilation, increased risk of nosocomial infections, and greater mortality
Understanding current evidence-based fluid management strategies is paramount for pediatric residents and specialists preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Sudden onset of severe dyspnea
Rapid breathing (tachypnea)
Increased work of breathing, including nasal flaring, retractions, and grunting
Cough, often non-productive initially
Cyanosis or pallor
Lethargy or decreased level of consciousness.
Signs:
Tachycardia
Hypotension or hypertension depending on underlying cause and shock status
Auscultation reveals diffuse crackles or diminished breath sounds
Chest X-ray shows bilateral opacities not fully explained by lobar collapse or consolidation
Arterial blood gas (ABG) demonstrating severe hypoxemia refractory to supplemental oxygen.
Diagnostic Criteria:
The Berlin Definition for ARDS is adapted for pediatrics
Key components include: 1
Acute onset (within 1 week of a clinical insult or new/worsening respiratory symptoms)
2
Respiratory failure not fully explained by cardiac factors or fluid overload
3
Bilateral opacities on chest imaging (X-ray or CT) not fully explained by effusions, lobar/lung collapse, or nodules
4
Severe hypoxemia: PaO2/FiO2 ratio < 300 mmHg
For infants, modified criteria may use lower thresholds, and oxygenation targets are age-adjusted.
Diagnostic Approach
History Taking:
Focus on the precipitating event: recent infection (pneumonia, sepsis), aspiration (vomiting, foreign body), trauma, near-drowning, or underlying comorbidities (immunodeficiency, congenital heart disease, neuromuscular disorders)
Timeline of symptom onset is crucial
History of fluid intake and output, and signs of cardiac dysfunction.
Physical Examination:
Comprehensive assessment of respiratory effort: respiratory rate, use of accessory muscles, grunting, nasal flaring
Palpate for chest wall tenderness
Auscultate for breath sounds, crackles, wheezes, and murmurs
Assess for peripheral edema and jugular venous distension to evaluate for fluid overload
Assess for signs of sepsis or shock.
Investigations:
Arterial blood gas (ABG) for oxygenation and ventilation assessment (PaO2, PaCO2, pH)
Complete blood count (CBC) to assess for infection
Blood cultures if sepsis is suspected
Chest X-ray or CT scan to identify infiltrates and rule out other causes
Echocardiography to assess cardiac function and rule out cardiogenic pulmonary edema
Inflammatory markers (CRP, procalcitonin)
Coagulation profile if disseminated intravascular coagulation (DIC) is suspected
Sputum Gram stain and culture if pneumonia is present
Toxicology screen if aspiration is suspected.
Differential Diagnosis:
Cardiogenic pulmonary edema (secondary to congenital heart disease, myocarditis)
Pulmonary hemorrhage
Diffuse pneumonia (bacterial, viral, fungal)
Pulmonary embolism
Acute lung injury from trauma or inhalation
Near-drowning
Acute exacerbations of chronic lung diseases (e.g., cystic fibrosis)
Congenital pulmonary airway malformations.
Management
Initial Management:
Immediate stabilization is critical
Optimize oxygenation with highest possible FiO2
Initiate mechanical ventilation
Secure airway and establish IV access
Treat underlying cause (e.g., antibiotics for pneumonia/sepsis).
Medical Management:
Lung-protective ventilation strategies: low tidal volumes (4-6 mL/kg ideal body weight), appropriate PEEP to maintain alveolar recruitment, and permissive hypercapnia
Sedation and analgesia
Neuromuscular blockade judiciously if severe ventilator dyssynchrony persists
Bronchodilators if bronchospasm is present.
Fluid Management Strategies:
The cornerstone of pediatric ARDS fluid management is a conservative or restricted fluid strategy
Aim for a negative or neutral fluid balance
Frequent assessment of fluid status: daily weights, intake/output charting, urine output, and assessment for peripheral edema
Consider diuretics (e.g., furosemide) if signs of fluid overload are evident and respiratory mechanics are compromised
Avoid fluid boluses unless hemodynamic compromise is present and not attributable to ARDS
Monitor central venous pressure (CVP) and cardiac output (if available) cautiously
Echocardiography can be invaluable in assessing fluid responsiveness.
Supportive Care:
Nutritional support: early enteral nutrition is preferred to minimize gut atrophy and translocation of bacteria
Consider parenteral nutrition if enteral is not feasible
Glycemic control
Prevention of ventilator-associated pneumonia (VAP) and other healthcare-associated infections
DVT prophylaxis (mechanical or pharmacologic depending on risk)
Prone positioning can improve oxygenation in moderate to severe ARDS
Consider extracorporeal membrane oxygenation (ECMO) for severe refractory hypoxemia despite maximal conventional management.
Complications
Early Complications:
Worsening hypoxemia and respiratory failure
Barotrauma and volutrauma from mechanical ventilation
Pneumothorax
Ventilator-associated pneumonia (VAP).
Late Complications:
Pulmonary fibrosis and long-term lung dysfunction (bronchopulmonary dysplasia)
Neurological sequelae (e.g., developmental delay)
Muscle weakness and deconditioning
Post-intensive care syndrome (PICS).
Prevention Strategies:
Adherence to lung-protective ventilation strategies
Judicious fluid management to prevent overload
Early initiation of enteral nutrition
Strict infection control protocols
Prompt treatment of underlying causes
Minimizing sedation and early mobilization where possible.
Prognosis
Factors Affecting Prognosis:
Severity of ARDS (oxygenation index)
Age of the child (infants may have worse outcomes)
Presence of comorbidities
Underlying cause of ARDS (sepsis and trauma generally associated with higher mortality)
Duration of mechanical ventilation and ICU stay
Development of complications like VAP or multi-organ dysfunction syndrome (MODS).
Outcomes:
Survival rates for pediatric ARDS have improved but remain significant
Survivors may experience short-term sequelae such as reduced lung function and exercise intolerance
Some children may develop long-term respiratory morbidity and neurodevelopmental deficits
Early and aggressive management, including appropriate fluid management, is crucial for improving outcomes.
Follow Up:
Children recovering from ARDS require comprehensive follow-up
This includes regular assessment of pulmonary function, growth and development monitoring, and rehabilitation services if needed
A multidisciplinary approach involving pulmonologists, physical therapists, and developmental specialists is often beneficial
Neurodevelopmental assessment should be a routine part of follow-up for infants and young children.
Key Points
Exam Focus:
Conservative fluid management is key in pediatric ARDS to prevent worsening pulmonary edema
Recognize pediatric ARDS using adapted Berlin criteria
Lung-protective ventilation strategies (low tidal volumes, PEEP) are mandatory
Consider ECMO for refractory hypoxemia
Understand common triggers: sepsis, pneumonia, aspiration.
Clinical Pearls:
Think fluid restriction FIRST in pediatric ARDS unless clear evidence of hypovolemia or shock
Daily weights are your friend
Echocardiography is invaluable for fluid assessment
Prone positioning can significantly improve oxygenation
Treat the underlying cause aggressively
Long-term follow-up is essential for survivors.
Common Mistakes:
Over-resuscitation with fluids leading to pulmonary edema and worsening ARDS
Aggressive fluid management in the absence of clear hypovolemia
Inadequate PEEP leading to alveolar collapse
Using high tidal volumes which can cause ventilator-induced lung injury
Neglecting nutritional support
Failure to identify and treat the underlying precipitating cause promptly.