Overview
Definition:
Pediatric Acute Respiratory Distress Syndrome (ARDS) is a severe, acute inflammatory lung injury characterized by diffuse pulmonary inflammation and widespread alveolar damage, leading to increased pulmonary vascular permeability and loss of lung volume
It is defined by specific criteria, including timing, oxygenation deficit, radiographic evidence, and exclusion of pulmonary edema from other causes.
Epidemiology:
Pediatric ARDS occurs in approximately 1.4 to 3.4 per 100,000 children annually, with incidence varying by age group and underlying conditions
Sepsis is the most common cause in critically ill children, followed by pneumonia and trauma
Mortality rates remain significant, ranging from 10% to 40% depending on severity and underlying etiology.
Clinical Significance:
Pediatric ARDS represents a life-threatening condition requiring prompt recognition and aggressive management in the intensive care unit
Optimal mechanical ventilation strategies and adjunctive therapies like proning are crucial for reducing lung injury, improving oxygenation, and ultimately decreasing mortality and morbidity in affected children.
Clinical Presentation
Symptoms:
Rapid onset of severe dyspnea
Tachypnea and increased work of breathing
Cough, sometimes productive
Fever, if associated with infection
Cyanosis or pallor.
Signs:
Hypoxemia refractory to supplemental oxygen
Bilateral diffuse pulmonary infiltrates on chest imaging
Increased respiratory rate and accessory muscle use
Tachycardia and potential hypotension
Diffuse crackles on lung auscultation.
Diagnostic Criteria:
The Pediatric Acute Respiratory Distress Syndrome Consensus Criteria (PALICC 2015) define ARDS as: acute onset, bilateral opacities on chest imaging not fully explained by effusions, lobar/lung collapse, or nodules, and respiratory compromise not fully explained by cardiac dysfunction or fluid overload
The severity is graded by the oxygenation index (OI) or PaO2/FiO2 ratio: Mild (OI 4-8 or PaO2/FiO2 201-300), Moderate (OI 8-16 or PaO2/FiO2 101-200), and Severe (OI > 16 or PaO2/FiO2 ≤ 100)
Specific age-adjusted criteria exist for infants and neonates.
Diagnostic Approach
History Taking:
Detailed history of the onset of respiratory symptoms
Identify potential underlying causes: recent infection, trauma, aspiration, sepsis, cardiac events, or underlying chronic lung disease
Note any comorbidities
Clarify timing of symptom onset relative to insult.
Physical Examination:
Thorough cardiorespiratory examination focusing on respiratory rate, pattern, work of breathing (intercostal retractions, subcostal retractions, nasal flaring), accessory muscle use, air entry, presence of crackles, wheezes, or diminished breath sounds
Assess for signs of sepsis or systemic illness
Monitor vital signs closely, including oxygen saturation.
Investigations:
Arterial blood gases (ABGs) to assess oxygenation (PaO2/FiO2), ventilation (PaCO2), and acid-base status
Complete blood count (CBC) with differential to evaluate for infection
C-reactive protein (CRP) and procalcitonin for inflammatory markers and infection screening
Blood cultures and other relevant cultures (e.g., sputum) if infection suspected
Chest X-ray (CXR) or CT scan for diffuse bilateral opacities
Echocardiography to rule out cardiac causes of pulmonary edema
Consider viral respiratory panel
Lactate for sepsis evaluation.
Differential Diagnosis:
Congenital heart disease with pulmonary edema
Neonatal pneumonia
Meconium aspiration syndrome
Pulmonary hemorrhage
Bronchiolitis obliterans
Pulmonary embolism (rare in children)
Acute exacerbation of underlying lung disease (e.g., cystic fibrosis)
Sepsis with direct lung involvement.
Management
Initial Management:
Immediate stabilization and admission to PICU
Secure airway and provide supplemental oxygen
Initiate mechanical ventilation as soon as hypoxemia is severe and refractory to non-invasive support
Obtain comprehensive history and physical examination
Start empiric antibiotics if infection is suspected
Ensure adequate fluid and hemodynamic management.
Lung Protective Ventilation:
The cornerstone of ARDS management
Target a low tidal volume (4-6 mL/kg predicted body weight - PBW) to minimize ventilator-induced lung injury (VILI)
Use a respiratory rate sufficient to maintain normocarbia, but consider permissive hypercapnia if needed
Set a moderate positive end-expiratory pressure (PEEP) to keep alveoli open, titrating to optimize oxygenation while avoiding excessive alveolar overdistension or hemodynamic compromise
Aim for plateau pressures < 30 cmH2O
Initial PEEP can be set based on OI or ARDSNet tables, then adjusted based on patient response.
Pron E Positioning:
Prone positioning is a rescue therapy for moderate to severe ARDS (PaO2/FiO2 < 150 mmHg) that has failed to improve with optimal mechanical ventilation
It redistributes lung aeration, recruits dorsal lung regions, improves V/Q matching, and facilitates secretion clearance
Patients should be kept in the prone position for at least 12-16 hours per day, or continuously if tolerated
Requires meticulous nursing care, airway management, and vigilant monitoring for complications such as facial pressure sores, corneal abrasions, or peripheral nerve injury.
Supportive Care:
Fluid management: maintain euvolemia or mild fluid restriction
Nutritional support: early enteral or parenteral nutrition
Sedation and analgesia: manage pain and anxiety to facilitate ventilation and reduce stress
Neuromuscular blockade: may be considered for severe ARDS with ventilator dyssynchrony or to improve synchrony with low tidal volume ventilation, but used judiciously and for short durations (e.g., 48 hours)
Surfactant therapy: still under investigation for routine use in pediatric ARDS
consider in specific etiologies like severe pneumonia
Consider inhaled nitric oxide (iNO) or extracorporeal membrane oxygenation (ECMO) for refractory hypoxemia.
Complications
Early Complications:
Ventilator-induced lung injury (VILI) from barotrauma, volutrauma, atelectrauma, and biotrauma
Pneumothorax or pneumomediastinum
Ventilator-associated pneumonia (VAP)
Hemodynamic instability, including hypotension and right heart failure.
Late Complications:
Pulmonary fibrosis and long-term lung sequelae
Ventilator dependence
Neuromuscular weakness (ICU-acquired weakness)
Psychological sequelae (anxiety, depression, PTSD)
Impaired neurodevelopmental outcomes in survivors, particularly in younger children.
Prevention Strategies:
Strict adherence to lung-protective ventilation strategies (low tidal volume, appropriate PEEP, limit plateau pressure)
Careful fluid management
Early mobilization and physiotherapy
Judicious use of sedation and neuromuscular blockade
Prone positioning for eligible patients
Meticulous oral care and elevation of the head of the bed for VAP prevention.
Prognosis
Factors Affecting Prognosis:
Severity of ARDS (based on OI/PaO2:FiO2)
Underlying etiology and comorbidities
Age at presentation (younger children may have poorer outcomes)
Promptness and effectiveness of management
Development of complications like sepsis or VAP.
Outcomes:
Mortality rates for pediatric ARDS range from 10% to 40%
Survivors may experience significant morbidity, including prolonged hospital stays, need for respiratory support, impaired lung function, and neurodevelopmental deficits
Early and aggressive lung-protective ventilation and timely proning can improve outcomes.
Follow Up:
Survivors of pediatric ARDS require comprehensive long-term follow-up
This includes regular pulmonary function tests, assessment for neurodevelopmental delays, psychological support, and management of any chronic respiratory issues
A multidisciplinary approach involving pulmonologists, developmental pediatricians, and therapists is essential.
Key Points
Exam Focus:
Remember the PALICC 2015 definition and severity grading for pediatric ARDS
Prioritize lung-protective ventilation: low tidal volumes (4-6 mL/kg PBW), permissive hypercapnia, and appropriate PEEP
Proning is a rescue therapy for moderate-severe ARDS with PaO2/FiO2 < 150 mmHg
Monitor plateau pressures (<30 cmH2O).
Clinical Pearls:
Always calculate tidal volumes based on Predicted Body Weight (PBW), not actual weight
Titrate PEEP to optimize oxygenation and compliance, avoiding overdistension
Proning requires a dedicated team and careful monitoring for complications
Consider the underlying cause of ARDS as it may influence management
Early recognition and PICU transfer are critical for survival.
Common Mistakes:
Using excessive tidal volumes or high respiratory rates, leading to VILI
Inadequate PEEP, resulting in alveolar collapse
Overzealous fluid resuscitation, exacerbating pulmonary edema
Delaying mechanical ventilation when indicated
Not considering proning in appropriate patients with refractory hypoxemia
Forgetting to adjust ventilation settings based on patient response and oxygenation goals.