1. Respiratory and Hemodynamic Support

Critically ill patients with massive pulmonary embolism (PE) may require mechanical ventilation or extracorporeal membrane oxygenation (ECMO) when respiratory failure or cardiogenic shock compromise gas exchange and hemodynamics. Support aims to optimize oxygenation while minimizing right ventricular (RV) afterload.

1.1 Mechanical Ventilation

Indications

• Refractory hypoxemia (PaO₂/FiO₂ ratio < 150 mmHg)
• Hypercapnia with evidence of respiratory muscle fatigue
• Altered mental status compromising airway protection

Initial Ventilator Settings

• Tidal Volume: 4–8 mL/kg of predicted body weight to prevent volutrauma.
• Plateau Pressure: Target ≤30 cm H₂O to minimize lung injury.
• PEEP: Start at 5–10 cm H₂O. Use cautiously, as high PEEP can decrease RV preload and worsen hemodynamics.
• FiO₂: Titrate to the lowest level needed to maintain SpO₂ ≥88–92%.

Adjunctive Therapies

• Prone Positioning: Consider for ≥12 hours per day in patients with a PaO₂/FiO₂ ratio < 150 mmHg to improve V/Q matching.
• Neuromuscular Blockade: A short course (24–48 hours) may be necessary for severe patient-ventilator dyssynchrony.

1.2 Extracorporeal Membrane Oxygenation (ECMO)

Patient Selection

• Veno-venous (VV) ECMO: Indicated for refractory hypoxemia despite optimal mechanical ventilation and proning.
• Veno-arterial (VA) ECMO: Indicated for refractory cardiogenic shock unresponsive to fluids, vasopressors, or thrombolysis.
• Ideal Candidate: A patient with a reversible cause of shock/hypoxia (i.e., the PE), minimal comorbidities, and no absolute contraindications to systemic anticoagulation.

Technical Considerations

• Cannulation: VV-ECMO typically involves femoral venous drainage to jugular venous return. VA-ECMO uses femoral venous drainage to femoral arterial return.
• Anticoagulation: Unfractionated heparin (UFH) is standard, typically initiated with a bolus of 50–100 IU/kg followed by an infusion of 10–20 IU/kg/h. Monitoring targets include an anti-Xa level of 0.3–0.7 IU/mL or an activated clotting time (ACT) of 180–220 seconds.

2. ICU-Related Complication Prevention

Prevention of stress ulcers and ICU-acquired infections is critical to reducing morbidity in ventilated or coagulopathic patients with VTE.

2.1 Stress-Related Mucosal Bleeding Prophylaxis

Prophylaxis is indicated for patients with high-risk features, including mechanical ventilation for >48 hours, coagulopathy (platelets <50×10⁹/L or INR >1.5), or shock requiring vasopressors.

• Proton Pump Inhibitors (PPIs): E.g., pantoprazole 40 mg IV daily. More effective at reducing GI bleeding but may be associated with a higher risk of Clostridioides difficile infection.
• Histamine-2 Receptor Antagonists (H₂RAs): E.g., famotidine 20 mg IV every 12 hours. Less potent but may have a better safety profile regarding nosocomial infections.

Prophylaxis should be discontinued once the primary ICU risk factors have resolved.

2.2 Infection Prevention

Ventilator-Associated Pneumonia (VAP) Bundles

• Elevation of the head of the bed to 30–45 degrees.
• Daily sedation vacations and spontaneous breathing trials to assess readiness for extubation.
• Routine oral hygiene with an antiseptic agent like chlorhexidine.
• Use of endotracheal tubes with subglottic secretion drainage.

Catheter-Associated Infections

• Central Lines: Adherence to a central line bundle, including maximal sterile barriers during insertion, chlorhexidine skin preparation, and daily review of line necessity.
• Urinary Catheters: Use only when strictly indicated and implement nurse-driven protocols for prompt removal.

3. Iatrogenic Complication Management

Prompt recognition and management of complications arising from therapy, such as heparin-induced thrombocytopenia (HIT) and major bleeding, are essential for patient safety.

3.1 Heparin-Induced Thrombocytopenia (HIT)

HIT is a prothrombotic, immune-mediated adverse drug reaction caused by antibodies against the platelet factor 4 (PF4)/heparin complex. It typically occurs 5–14 days after heparin exposure. The 4Ts score is a clinical tool used to estimate the pretest probability of HIT.

Pharmacotherapy for HIT

3.2 Bleeding Management

Management of major bleeding requires immediate cessation of the anticoagulant, administration of a specific reversal agent if available, and supportive care with transfusions and hemodynamic support.

Transfusion and Hemodynamic Support

• Red Blood Cells (RBCs): Transfuse to maintain a hemoglobin target of 7–8 g/dL (a higher target may be considered in active ischemia).
• Platelets: Transfuse for active bleeding if platelet count is <50×10⁹/L.
• Vasopressors: Use as needed to support mean arterial pressure and organ perfusion during hemorrhagic shock.

4. Multidisciplinary Goals-of-Care

Early, structured goals-of-care discussions are crucial to ensure that invasive therapies align with the patient’s values and prognosis.

4.1 The PERT Model

The Pulmonary Embolism Response Team (PERT) model formalizes a multidisciplinary approach. The team typically includes an intensivist, cardiologist, interventional radiologist, hematologist, pharmacist, and specialized nursing staff.

4.2 Discussion Timing and Structure

Discussions should be initiated within 24 hours of a high-risk PE diagnosis. Key components include:

• A clear explanation of the diagnosis and prognosis.
• A discussion of all available therapeutic options (e.g., anticoagulation, thrombolysis, catheter-directed therapy, ECMO).
• Eliciting the patient’s (or surrogate’s) values and preferences.
• Establishing and documenting a code status.

5. Protocol Development and Quality Metrics

Standardized institutional pathways and consistent tracking of quality metrics are foundational to providing high-quality care and supporting continuous improvement.

5.1 Institutional Pathways and Order Sets

Developing standardized order sets can improve safety and efficiency. Examples include:

• Weight-based anticoagulation titration protocols.
• Thrombolysis eligibility checklists and administration protocols.
• Clear triggers for PERT activation or surgical consultation.
• ECMO activation criteria and protocols.

5.2 Outcome Monitoring and Quality Improvement

Regularly tracking key performance indicators is essential. Important metrics include:

• Ventilator-free days at day 28.
• Incidence of major bleeding and HIT.
• ICU and hospital length of stay (LOS).
• 30-day and in-hospital mortality.

These metrics should be reviewed in multidisciplinary meetings to identify areas for improvement.