What is the treatment approach for a patient with Acute Respiratory Distress Syndrome (ARDS)?

Treatment of Acute Respiratory Distress Syndrome (ARDS)

All patients with ARDS require immediate implementation of lung-protective mechanical ventilation with tidal volumes of 4-8 mL/kg predicted body weight and plateau pressures ≤30 cmH₂O, and those with severe ARDS (PaO₂/FiO₂ <100 mmHg) must receive prone positioning for >12 hours daily, as these are the only interventions proven to reduce mortality. 1, 2

Severity Classification and Initial Assessment

• Classify ARDS severity immediately using the Berlin Definition based on PaO₂/FiO₂ ratio: mild (201-300 mmHg), moderate (101-200 mmHg), or severe (<100 mmHg) 1, 3, 4
• Identify and aggressively treat the underlying cause (pneumonia, sepsis, trauma, pancreatitis), as this is the only causal treatment 2, 5
• For COVID-19 pneumonia specifically, administer dexamethasone 2

Initial Respiratory Support Strategy

For Mild ARDS Only

• Consider high-flow nasal cannula (HFNC) at 30-40 L/min with FiO₂ 50-60% only if the patient is hemodynamically stable, alert, cooperative, and does NOT have pneumonia as the ARDS etiology 2, 3
• Proceed immediately to intubation in a controlled setting if any of the following occur within 1 hour: deterioration, FiO₂ exceeds 70%, or flow exceeds 50 L/min 2, 3
• Absolute contraindications to HFNC include hypercapnia, hemodynamic instability, multi-organ failure, altered mental status, or inability to protect airway 3

For Moderate to Severe ARDS

• Proceed directly to intubation in a controlled setting rather than attempting non-invasive ventilation, as failure rates are unacceptably high 3

Mandatory Lung-Protective Mechanical Ventilation

These settings apply to ALL intubated ARDS patients regardless of severity:

• Set tidal volume at 4-8 mL/kg predicted body weight (not actual body weight) 1, 2
• Maintain plateau pressure ≤30 cmH₂O at all times 1, 2
• Target SpO₂ 92-96% and PaO₂ 70-90 mmHg—do not exceed SpO₂ 96% to avoid oxygen toxicity 2, 3

PEEP Strategy for Moderate to Severe ARDS

• Apply higher PEEP using the ARDS Network PEEP-to-FiO₂ grid in patients with moderate to severe ARDS 1, 2
• Monitor continuously for hemodynamic compromise, as higher PEEP can impair venous return and right ventricular function 1, 2
• Do NOT use prolonged lung recruitment maneuvers in combination with high PEEP—this carries a high probability of harm from adverse hemodynamic effects 1

PEEP Strategy for Mild ARDS

• Use lower PEEP in mild ARDS, as higher PEEP shows no benefit and potential trend toward harm in this population 1

Mandatory Adjunctive Therapy for Severe ARDS

Prone Positioning

For severe ARDS (PaO₂/FiO₂ <100 mmHg):

• Implement prone positioning for >12 hours per day immediately—this is a strong recommendation with proven mortality reduction 1, 2, 6
• Apply deep sedation and analgesia during prone positioning 3
• Continue daily prone sessions until oxygenation improves to moderate ARDS range 2, 3

Conditional Adjunctive Therapies for Severe ARDS

Neuromuscular Blocking Agents

• Consider cisatracurium infusion for 24-48 hours in early severe ARDS (within first 48 hours of onset) to improve ventilator synchrony, reduce oxygen consumption, and potentially improve outcomes 1, 2, 3
• This is particularly beneficial when ventilator-patient dyssynchrony persists despite adequate sedation 3

Corticosteroids

• Consider corticosteroids in ARDS, particularly in cases associated with acute pancreatitis or persistent inflammation 1, 6

Fluid Management Strategy

• Implement conservative fluid management to minimize pulmonary edema while maintaining adequate organ perfusion 2, 3, 7
• Monitor fluid balance meticulously—excessive fluid administration worsens oxygenation, promotes right ventricular failure, and increases mortality 3
• For ARDS in acute pancreatitis specifically: limit total crystalloid to <4000 mL in first 24 hours after initial resuscitation 6

Hemodynamic Monitoring and Right Ventricular Protection

• Assess right ventricular function via echocardiography, as RV failure significantly worsens outcomes 2, 3
• Maintain adequate diastolic filling without causing RV overdistension 1
• Avoid acidosis, maintain oxygenation, and use well-selected vasopressors to support RV function 1

Advanced Therapies for Refractory Hypoxemia

VV-ECMO

• Consider veno-venous ECMO in selected patients with severe ARDS who fail conventional management, particularly those with potentially reversible disease and no contraindications 1, 3, 7
• VV-ECMO should only be implemented at centers with ECMO expertise 3
• Blood is extracted from the femoral vein and returned to the right atrium through the internal jugular vein after membrane oxygenation 3

Inhaled Pulmonary Vasodilators

• Consider a trial of inhaled pulmonary vasodilators as rescue therapy for severe hypoxemia, but discontinue immediately if no rapid improvement in oxygenation occurs 3

Supportive Care Measures

• Provide stress ulcer prophylaxis and venous thromboembolism prophylaxis 8
• Initiate enteral nutrition early to prevent gut failure and infectious complications—both gastric and jejunal feeding are safe 6, 8
• Consider prophylactic antibiotics in severe cases with evidence of pancreatic necrosis 6

Monitoring Requirements

• Monitor continuously: oxygen saturation, respiratory mechanics (driving pressure, mechanical power), hemodynamics, and arterial blood gases 2, 3
• Assess for ventilator-patient dyssynchrony 3
• Perform serial echocardiography to detect acute cor pulmonale 1, 3

Weaning from Mechanical Ventilation

• Perform daily spontaneous breathing trials once the patient's condition improves, as this consistently reduces duration of mechanical ventilation 3
• Use the Rapid Shallow Breathing Index (RSBI): values >105 breaths/min/L indicate likely need to continue mechanical ventilation 3
• Consider noninvasive ventilation after extubation for patients at high risk for extubation failure 3

Critical Pitfalls to Avoid

• Do NOT use high-frequency oscillatory ventilation routinely in moderate or severe ARDS—this is a strong recommendation against its use 1
• Do NOT delay prone positioning in severe ARDS—underutilization of this proven therapy is associated with increased mortality 1, 6, 3
• Do NOT administer excessive fluids, blood products, or use injurious mechanical ventilation—these aggravate lung injury 2, 6
• Do NOT use prolonged lung recruitment maneuvers with high PEEP strategies—this causes hemodynamic harm 1
• Do NOT target normal oxygen saturations—permissive hypoxemia (SpO₂ 92-96%) is appropriate 2, 3
• Do NOT use β2 agonists, statins, or keratinocyte growth factor—these have shown no benefit and possible harm 4