What is the best management approach for a patient with scrub typhus, severe left ventricular (LV) dysfunction, acute pulmonary edema, and Acute Respiratory Distress Syndrome (ARDS), considering Extracorporeal Membrane Oxygenation (ECMO) configuration?

ECMO Configuration for Scrub Typhus with Severe LV Dysfunction, Acute Pulmonary Edema, and ARDS

In a scrub typhus patient presenting with severe left ventricular dysfunction AND acute pulmonary edema AND ARDS, veno-arterial (VA) ECMO is the required configuration because this represents combined cardiopulmonary failure requiring both hemodynamic support and respiratory support. 1

Configuration Selection Algorithm

VA-ECMO is mandated when:

• Severe LV dysfunction confirmed by echocardiography with reduced ejection fraction 1
• Cardiogenic shock with very low cardiac output 1
• Requirement for significant inotropic support and/or norepinephrine >0.5 µg/kg/min 1
• Combined respiratory failure (ARDS) with hemodynamic instability 1

VV-ECMO would be insufficient because it provides only respiratory support without hemodynamic augmentation, and this patient has severe cardiac dysfunction requiring circulatory support 1

Critical Management Considerations

Pre-ECMO Optimization

• Initiate lung-protective ventilation with tidal volumes 4-8 mL/kg predicted body weight and plateau pressure ≤30 cmH₂O 2
• Apply prone positioning for >12 hours if PaO₂/FiO₂ <150 mmHg 2, 3
• Consider neuromuscular blockade for early severe ARDS (conditional recommendation) 2
• Optimize PEEP based on gas exchange, hemodynamic status, and lung recruitability while avoiding excessive mean airway pressures that worsen RV function 2, 3

Specific Concerns in Scrub Typhus with Cardiac Involvement

Scrub typhus can cause fulminant myocarditis with rapid progression to cardiac arrest 4, making early recognition and aggressive support critical. The combination of ARDS (present in all severe scrub typhus ICU patients) and cardiogenic shock carries 56% mortality even with ventilator and vasopressor support 5.

VA-ECMO Specific Management

Left ventricular decompression is essential because VA-ECMO increases LV afterload and can cause:

• Severe pulmonary edema from LV distension 2, 6
• Pulmonary hemorrhage 6
• Prevention of myocardial recovery 6

Decompression strategies include:

• Intra-aortic balloon pump (IABP) 2
• Impella device 2
• Blade and balloon atrial septostomy (BBAS) to create right-to-left shunt, reducing left atrial pressure from mean 30.5 mmHg to 16 mmHg 6

Hemodynamic Monitoring Requirements

Continuous monitoring must include: 2, 1

• Arterial blood pressure
• ECMO flow rates
• Repeated echocardiography (essential for VA-ECMO to assess LV distension and function) 2, 1
• Central venous oxygen saturation
• Lactate levels
• Fluid balance (positive fluid balance independently predicts poor outcomes) 2

Note: Continuous thermodilution-based and pulse contour analysis-based cardiac output monitoring are NOT recommended during ECMO as they produce inaccurate results 2

Institutional Requirements

Transfer to an ECMO center is mandatory if current facility lacks:

• Minimum annual volume of 20-25 ECMO cases 1
• 24/7 availability of multidisciplinary ECMO team (physicians, nurses, perfusionists, ECMO specialists) 1
• Nurse-to-patient ratio of at least 1:1 to 1:2 1
• Quality assurance review procedures 1

Mobile ECMO teams should retrieve patients from non-ECMO centers when the patient meets criteria but cannot be safely transported without ECMO support 1

Antimicrobial Therapy

Doxycycline is the definitive treatment for scrub typhus and must be initiated immediately 7, 8:

• Intravenous doxycycline for critically ill patients 8
• Consider adding oral azithromycin for potential concurrent bacterial pneumonia 8

Complications and Monitoring

Bleeding complications occur in 75.3% of VA-ECMO patients (versus 37% in VV-ECMO) 1, with acquired von Willebrand syndrome developing in almost all ECMO patients within hours 1

Thrombotic events occur in 42% of patients despite anticoagulation 1

Right ventricular failure may develop from high PEEP and driving pressures, occurring in 20-25% of severe ARDS patients 3. This requires:

• Reducing driving pressure to <18 cmH₂O 3
• Avoiding fluid boluses (deleterious in RV failure) 3
• Maintaining MAP ≥65 mmHg with norepinephrine 3
• Considering inhaled pulmonary vasodilators (nitric oxide or prostacyclin) 3

Prognostic Factors in Scrub Typhus

Mortality predictors requiring heightened vigilance: 5

• Increasing age (OR 1.211 per year)
• Serum creatinine >1.4 mg/dL (OR 0.110)
• Requirement for >1 vasopressor (OR 40.647)

The median duration of mechanical ventilation in scrub typhus with ARDS and shock is 53 hours, with vasopressor use for 48 hours 5, indicating that survivors typically show improvement within 2-3 days of appropriate therapy.