Management of ARDS with Suspected Superimposed Infection

Diagnostic Approach

The American Thoracic Society recommends obtaining tracheal aspirate cultures immediately before initiating or changing antibiotics in patients with suspected ventilator-associated pneumonia 1
Samples of lower respiratory tract secretions should be obtained from all patients with suspected hospital-acquired pneumonia or ventilator-associated pneumonia, and must be collected before antibiotic changes 1
Tracheal aspirate cultures provide valuable diagnostic information and can identify the causative pathogen(s) in most cases of pulmonary infection 1
Leukocytosis (WBC >14,000 cells/mm³) or left shift (band neutrophils ≥6% or total band count >1500/mm³) warrants careful assessment for bacterial infection 3
Hypoxemia (oxygen saturation <90%) is a predictor of impending respiratory failure and 30-day mortality 4, 5

The American College of Chest Physicians recommends initiating broad-spectrum empiric antibiotics immediately after obtaining cultures in patients with suspected ventilator-associated pneumonia 1, 9
Continue lung-protective ventilation with tidal volumes 6 mL/kg predicted body weight 1
Maintain plateau pressures <30 cm H2O 1
Consider prone positioning if PaO2/FiO2 ratio <150 despite optimization 10
For early moderate to severe ARDS (PaO2/FiO2 <200 within 14 days of onset), corticosteroids are recommended 10

Once culture results return, narrow antibiotics to target identified pathogens 1
Consider de-escalation after 48-72 hours if cultures negative and clinical improvement 1

Patients with reduced respiratory system compliance appear to sustain greater survival benefit from low tidal volume ventilation 11
Physiologic measurements can predict benefit or harm of interventions in individual patients 11
The American Thoracic Society notes that ARDS represents a heterogeneous syndrome with multiple pathophysiologic processes present to varying degrees within individual patients 6
Immunocompromised patients (HIV, functional asplenia) were largely excluded from major ARDS trials, making this population higher risk with potentially different treatment responses 7