Pulmonary Embolism, Pulmonary Hypertension and Pulmonary Edema

Acute Pulmonary Embolism: Risk Stratification and Emergent Interventions

Acute pulmonary embolism triggers an abrupt increase in alveolar dead space. This creates an area of the lung that receives ventilation without perfusion, producing acute ventilation-perfusion mismatch. Bedside assessment frequently reveals tachypnea and sinus tachycardia as common early findings, while new, unexplained dyspnea is a particularly common presenting symptom. A 12-lead electrocardiogram obtained to evaluate acute right ventricular strain may show an S1Q3T3 pattern, right bundle branch block, or T-wave inversions in leads V1 through V4.

Clinical risk stratification guides immediate critical care priorities. High-risk, or massive, pulmonary embolism involves hemodynamic instability, including cardiac arrest, obstructive shock requiring vasopressors, or persistent hypotension not explained by another cause. Conversely, submassive pulmonary embolism presents with normal systemic blood pressure but reveals underlying right ventricular dysfunction or elevated cardiac biomarkers, such as troponin and BNP. Computed tomography pulmonary angiography serves as the usual first-line imaging test to confirm suspected pulmonary embolism in a hemodynamically stable patient when contrast and transport are appropriate.

For non-high-risk presentations, unfractionated heparin infusions require systematic titration guided by activated partial thromboplastin time or anti-factor Xa levels per institutional protocol. When high-risk pulmonary embolism causes hemodynamic instability, the provider evaluates bleeding risk and contraindications to prescribe systemic thrombolysis. The critical care nurse monitors closely for hemorrhage and hemodynamic recovery. Active internal bleeding, ischemic stroke within the preceding three months, and a history of intracranial hemorrhage are generally considered major or absolute contraindications, though the treating team weighs these risks in immediately life-threatening circumstances. Any sudden change in neurological status during a thrombolytic infusion necessitates immediate cessation of the infusion and urgent provider notification to evaluate for intracranial hemorrhage.

When systemic thrombolysis is contraindicated or has failed in high-risk pulmonary embolism, the treating team may consider surgical embolectomy or catheter-based intervention. An inferior vena cava filter may be considered when acute venous thromboembolism cannot be treated with anticoagulation. If recurrent pulmonary embolism occurs despite verified therapeutic anticoagulation, the provider must reassess the patient before a filter is considered.