Pulmonary Embolism: Pathophysiology, Diagnosis, and Nursing Management

Pulmonary embolism (PE) is a life-threatening obstruction of pulmonary blood flow, most often from a dislodged deep vein thrombosis. This note reviews the pathophysiology, risk factors, presentation, diagnostics, treatment, and nursing priorities you need for safe care and exam readiness.

What Is Pulmonary Embolism?

• Pulmonary embolism occurs when a blood clot travels from the venous system to the lungs and lodges in a pulmonary artery, blocking blood flow.
• Most clots originate from deep vein thrombosis (DVT) in the legs.
• The blockage causes a ventilation–perfusion (V/Q) mismatch, hypoxemia, and increased pulmonary vascular resistance.
• Massive PE can cause right ventricular failure and hemodynamic collapse.

Pathophysiology

• A thrombus forms in the deep veins, usually in the lower extremities.
• The clot breaks loose and travels through the venous system to the right side of the heart.
• It lodges in a pulmonary artery or one of its branches, obstructing flow to the affected lung segment.
• Alveoli continue to ventilate but are not perfused, creating dead space.
• The resulting V/Q mismatch causes severe hypoxemia.
• Pulmonary vascular resistance rises, producing right ventricular strain.
• Right ventricular failure can lead to decreased cardiac output and shock.

Risk Factors (Virchow's Triad)

• Venous stasis: immobility, prolonged bed rest, recent surgery, long travel, obesity, pregnancy.
• Vascular injury: trauma, surgery, fractures, central venous catheters.
• Hypercoagulability: cancer, oral contraceptives, hormone therapy, inherited clotting disorders, smoking.

Mnemonic — "STASIS": Surgery, Trauma, Age, Stasis, Immobility, Sickness (cancer, heart failure).

Clinical Presentation

• Symptoms: sudden dyspnea (most common), pleuritic chest pain, cough, hemoptysis, anxiety, sense of impending doom.
• Vital signs: tachypnea, tachycardia, hypoxemia, possible hypotension.
• Physical findings: crackles, decreased breath sounds, jugular venous distension (JVD), leg swelling from DVT.
• Massive PE signs: hypotension, syncope, signs of right heart failure (JVD, peripheral edema, hepatomegaly).

Diagnostic Tests

• Wells score determines pretest probability for PE.
• D-dimer is a fibrin degradation product; a negative result rules out PE in low-risk patients but is not specific.
• CT pulmonary angiography (CTPA) is the preferred imaging study — the gold standard.
• Ventilation–perfusion (V/Q) scan is an alternative if CTPA is contraindicated.
• Echocardiogram assesses right ventricular strain and excludes other causes.
• Arterial blood gas typically shows hypoxemia and respiratory alkalosis.
• ECG may show sinus tachycardia, right axis deviation, or the classic S1Q3T3 pattern.

Risk Stratification

• Massive (high-risk): hemodynamically unstable (SBP <90 mmHg or drop >40 mmHg). → Emergent thrombolytics or embolectomy.
• Submassive (intermediate-risk): stable, but with right ventricular dysfunction or elevated troponin. → Anticoagulation with close monitoring.
• Low-risk: stable, no RV dysfunction, normal troponin. → Anticoagulation; may be managed as outpatient.

Management

Oxygen and Supportive Care

• Administer high-flow oxygen to maintain SpO₂ above 92%.
• Establish two large-bore IV lines.
• For massive PE with hypotension, give cautious IV fluids (≤500 mL bolus) to avoid volume overload.
• Start vasopressors (norepinephrine) if hypotension persists.

Anticoagulation (First-Line)

• Apixaban 10 mg twice daily for 7 days, then 5 mg twice daily.
• Rivaroxaban 15 mg twice daily for 21 days, then 20 mg daily.
• Enoxaparin 1 mg/kg twice daily for hospitalized or unstable patients.
• Unfractionated heparin IV for critically ill patients requiring rapid reversal.

Thrombolytics (Massive PE Only)

• Alteplase (tPA) is given for massive PE with hemodynamic instability.
• Thrombolytics dissolve the clot rapidly but carry a high bleeding risk.
• Absolute contraindications: active bleeding, recent stroke, recent major surgery.

Complications

• Right heart failure from increased pulmonary pressures.
• Cardiogenic shock from severe right heart failure.
• Pulmonary infarction from complete vessel occlusion.
• Recurrent PE despite treatment.
• Bleeding from anticoagulation or thrombolytics.
• Mortality in massive PE is approximately 10–30%.

Nursing Assessment

• Monitor vital signs continuously, including blood pressure and heart rate.
• Assess oxygen saturation and titrate oxygen to keep SpO₂ above 92%.
• Auscultate lung sounds for crackles or decreased breath sounds.
• Assess chest pain: location, quality, and relationship to breathing.
• Monitor for right heart failure: JVD, peripheral edema.
• Assess for bleeding if the patient is on anticoagulation.
• Inspect legs for DVT: swelling, pain, warmth, redness.

Nursing Interventions

• Administer oxygen and position patient in high-Fowler's to facilitate breathing.
• Administer anticoagulants exactly as ordered.
• Monitor for bleeding: dark stools, hematuria, bruising, epistaxis.
• Monitor for recurrent PE: new chest pain, worsening dyspnea.
• Provide emotional support for anxiety and fear.
• Keep resuscitation equipment at the bedside.
• For patients receiving thrombolytics, monitor all sites for bleeding.
• Avoid unnecessary venipunctures and IM injections.

Patient Teaching

• Take anticoagulants exactly as prescribed; never skip doses.
• Report signs of bleeding: dark stools, coffee-ground vomit, unusual bruising.
• Use a soft toothbrush and electric razor.
• Wear medical alert identification.
• Avoid aspirin, NSAIDs, and other blood thinners unless approved.
• Move legs frequently during long trips.
• Wear compression stockings as prescribed.

Common NCLEX Traps

• Massive PE causes hypotension and shock, not just dyspnea.
• D-dimer is sensitive but not specific; a positive result requires imaging.
• CTPA is the gold standard — not the V/Q scan.
• Thrombolytics are only for massive PE with hemodynamic instability.
• Anticoagulation does not dissolve clots; it prevents extension.
• IV fluids must be given cautiously; overload worsens right heart failure.
• INR monitors warfarin; DOACs (e.g., apixaban) do not require INR.
• A normal chest X-ray does not rule out PE.

Key takeaways

• PE most often results from a dislodged DVT that obstructs pulmonary flow and causes a V/Q mismatch with hypoxemia.
• Use Virchow's triad (stasis, vascular injury, hypercoagulability) to identify at-risk patients.
• Diagnose with Wells score + D-dimer + CTPA (gold standard).
• Anticoagulation is first-line; thrombolytics (alteplase) are reserved for massive, unstable PE.
• Nursing priorities: maintain SpO₂ >92%, high-Fowler's positioning, monitor for bleeding and right heart failure, and provide emotional support.
• Teach strict medication adherence, bleeding precautions, and DVT prevention strategies.