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20.13 Pulmonary Embolism

Table of Contents

20.13.1 Acute Pulmonary Embolism

Clinical Spectrum less than two weeks

  • Sudden onset of dyspnoea often with unexplained anxiety (most common)
  • Pleuritic chest pain and haemoptysis
  • Massive embolism: pleuritic chest pain, cyanosis, right heart failure and shock. Minor emboli or pulmonary infarction may herald massive embolism and must be treated vigorously
  • About 90% of emboli are from proximal leg deep vein thromboses (DVTs) or pelvic vein thromboses. DVTs are at risk for dislodging and migrating to the lung circulation. Thus, termed as venous thromboembolism (VTE).

Diagnostic Criteria

Determination pre-est probability of PE

Use validated scoring system: Wells Score 25

  • Score > 6.0–High clinical probability proceeds with imaging test to confirm PE and treat,
  • Score 2.0 to 6.0–Moderate clinical probability; negative D–dimer, PE is excluded. and D– dimer positive, obtain imaging tests to confirm based on result treat.
  • Score < 2.0–Low clinical probability negative D–dimer, PE is excluded. Positive D–dimer obtain imaging tests to confirm or rule out and based on result treat Alternatively
  • Score > 4–PE likely, d–dimer positive proceeds with diagnostic imaging to confirm and treat PE.
  • Score 4 or less–PE unlikely, consider d–dimer to rule out PE.

Table 20.11: Wells Score

Variable Score
Clinically suspected DVT 3.0 points
alternative diagnosis is less likely than PE 3.0 points
Tachycardia (heart rate > 100) 1.5 points
Immobilization (≥ 3d)/surgery in previous four weeks 1.5 points
History of DVT or PE 1.5 points
Hemoptysis 1.0 points
Malignancy (with treatment within six months) or palliative 1.0 points
  • ECG – Not reliable test for diagnosis may be normal. However,
  • Sinus tachycardia most common feature, acute right ventricular strain – i.e. right axis shift, S1Q3T3 occurs in small percentage of cases, may develop acute bundle branch block – right or left, may simulate right ventricular infarction, may develop arrhythmias – eg atrial fibrillation
  • Arterial blood gases; not diagnostic, the pO2 decreased <60mmHg due ventilation/perfusion mismatch. pCO2 decreased due to hyperventilation, pH increased but may decrease in shocked patient
  • D–dimer test – very sensitive blood test, but not specific. A negative test d– dimer test excludes an embolus in majority of cases (best exclusive test to rule out PE when is negative)
  • Chest X–ray – Not very reliable usually normal, diaphragm may be raised on affected area, atelectasis may occur, peripheral wedge–shaped shadow & plural effusion
  • Cardiac Echocardiography; Useful in diagnosis, features suggestive or support
  • evidence of massive embolus acute right ventricular strain
  • Computer Tomography Pulmonary Angiogram Scan (CTPA); Useful can demonstrate the presence and extent of proximal pulmonary emboli
  • Ventilation/Perfusion Scan; Useful in stable patient to confirm the diagnosis. The presence of a perfusion defect with normal ventilation not corresponding to an x–ray abnormality is characteristic
  • Pulmonary Angiography: Still gold standard investigation, may be necessary to establish
  • diagnosis and catheter based embolectomy in the catheterization lab.

Non-Pharmacological Treatment

  • Administer O2 – maintain pO> 60mmHg,
  • Treat shock
  • Correct electrolyte & acid base abnormalities and arrhythmias
  • Ventilate if patient in respiratory failure

Pharmacological Treatment

Anticoagulation

D: Heparin (UFH) 10,000units IV bolus, then maintenance infusion starts with 6,000U over 6 hours to keep PTT or clotting time 2–3 times above baseline. PTT should be performed 12 hourly per lab instruction.

OR

D: Enoxaparin 1mg/kg twice daily

Start warfarin after 24 hours of heparin and continue post discharge for long–term. If the aetiology unknown may be for life, if aetiology is established at least for six months. Maintain INR 2.0–3.0

Thrombolytic (Fibrinolysis)

Indicated in proximal massive pulmonary emboli and haemodynamically unstable if no contra–indication exists

C: Streptokinase 250,000 IU infusion over 30 minutes, then 100,000 IU per hour for 24 hours

OR

D: Alteplase (rtPA) 100mg IV infusion over 2hours

Referral

All cases suspected of pulmonary embolus should be referred to a high level of care – specialized hospital care with HCDU/ICU

20.13.2 Chronic Pulmonary Embolism

Chronic pulmonary emboli are mainly a consequence of incomplete resolution of acute pulmonary thromboembolism. Clinically symptoms and signs may be preceded by Acute PE for more than two weeks.

Diagnostic Criteria

Refer or Section 6.11.2 majority of patients present with features of pulmonary hypertension

Pharmacological Treatment

Long-term oral anticoagulation

S: Warfarin 2–10mg once a day orally

Maintain INR 2.0–3.0

Referral: All cases suspected of pulmonary embolus should be referred to a high level of care

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