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Respiratory > 5.1 Pulmonary Embolism > Flashcards

5.1 Pulmonary Embolism Flashcards

1
Q

Embolism

A

Obstruction of blood vessel by foreign substance or blood clot that travels through blood stream, lodging in blood vessel - plugging the vessel

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2
Q

Types of emboli

A
  • Thrombus
  • Tumour
  • Air - after surgery
  • Fat - after trauma
  • Amniotic fluid - after labour
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3
Q

Pulmonary embolism

A
  • In daily practice - refers to a thrombus emboli
  • Emboli enters right side of heart and pulmonary arteries
  • 90% of PE’s arise from DVT’s (most common cause)
  • Most preventable and unexpected of hospital deaths
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4
Q

Virchow’s Triad

A

Increased risk of clotting:
• Endothelial injury - e.g. trauma/surgery
• Stasis/turbulence of blood flow - can cause propogation of clot
• Blood hypercoagulability

• Inflammation can act through any of the three above to predispose an individual to clotting

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5
Q

Hypercoagulability states

A
  • Prior thrombosis
  • Immobility
  • Malignancy
  • DIC
  • HRT (Hormone replacement therapy - oestrogens)
  • Pregnancy
  • Prolonged travel
  • Surgery
  • Oral contraceptive pill
  • Heart failure
  • Thrombophilia
  • Severe burns
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6
Q

Consequences of PE

A
  • Hypoxaemia - due to V/Q mismatch (>1)
  • Right sided heart failure - obstruction of pulmonary circulation causes right sided strain/hypertrophy/failure
  • Pulmonary infarction - but rare due to collateral vessels (bronchial arteries) which maintain perfusion slightly
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7
Q

Fat emboli

A

• Normally resolve spontaneously
• Can give rise to fat embolism syndrome (FES):
- traumatic causes: fracture of femur/pelvis/tibia and or massive soft tissue injury/severe burns/bone marrow biopsy’s etc.
- non traumatic causes: acute pancreatitis / fatty liver / haemoglobinopathies etc.
• Seen as petechial rash, decreased level of consciousness and SOB

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8
Q

Amniotic fluid emboli

A
  • Sudden, unexpected maternal collapse associated with hypotension/hypoxaemia/DIC
  • Occurs when amniotic fluid or fetal cells/hair along with other debris enter maternal circulation
  • Most cases occur during or immediately after labour
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9
Q

Covid-19

A

• Risks of venous thromboembolism (VTE) increased with covid-19 (due to severe inflammation)

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10
Q

Hypercoagulable disorders

A
  • Antithrombin III deficiency
  • Protein C or S deficiency
    • Factor V Leiden mutation - resistance to protein C (anti-coagulation proteins) is the most common risk factor
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11
Q

How does PE: acute right ventricular overload

A

• Pulmonary artery pressure increases due to PE if >30% of artery is occluded
• Leads to acute right ventricular dilatation and strain
• + inotropes released in attempt to maintain BP:
- increase contractility of heart and constrict pulmonary arteries which worsens condition
- puts more strain on right side of heart
• In about ⅓ of PE patients have patent foramen ovale allowing for right-to-left shunting
- May lead to severe hypoxaemia and paradoxical embolisation (from vein to artery)

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12
Q

How does PE: respiratory failure

A
  • Areas of V/Q mismatch (lower perfusion so V/Q>1)
  • Low right ventricle output
  • Shunt with patent foramen ovale
  • All cause hypoperfusion to the lungs
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13
Q

How does PE: pulmonary infarction

A
  • Small distal emboli may create areas of alveolar haemorrhage
  • May result in haemoptysis, pleuritis and small pleural effusion
  • May be visible of CXR as wedge shape
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14
Q

Symptoms of PE - most common to least common

A
  • Dyspnoea - SOB
  • Pleuritic chest pain - somatic - sharp/localised/acute
  • Cough
  • Substernal chest pain
  • Haemoptysis
  • Fever
  • Syncope
  • Unilateral leg pain
  • Chest well tenderness
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15
Q

Signs of PE - most common to least common

A
  • Tachypnoea - increased RR
  • Decreased breath sounds
  • Accentuated second heart sound (pulmonic artery sound much louder)
  • Tachycardia
  • Fever
  • Diaphoresis (sweating)
  • Lower extremity oedema
  • Cardiac murmur
  • Central cyanosis (due to hypoxaemia)
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16
Q

Investigations for PE

A

• ABG - may show hypoxaemia and hypocapnia (due to hyperventilation)
• CXR - common finding in PE is a normal CXR (wedge shaped infiltrate = pleural effusion)
• ECG - Sᵢ Qᵢᵢᵢ Tᵢᵢᵢ
- Deep S wave in lead I, Q wave in III and T wave in III
- T wave inversion also shown in right and inferior leads
- May also show tachycardia
- Also done to exclude MI/angina
• D dimer - normal range rules out PE
- in those who have a high likelihood of getting a PE, this investigation alone is not enough

17
Q

Clinical Probability Score

A
  • Wells’ score are used
  • 2 outcomes - likely and unlikely
  • If score >4 imaging is recommended
18
Q

Saddle embolus

A
  • At main bifurcation of an artery

* In PE, the saddle embolus would be straddling the pulmonary trunk

19
Q

Treatment of PE

A

• LMW heparin - to reduce chance of heparin-induced thrombocytopenia
• Oxygen
• After initial heparin - started on oral anticoagulant (rivaroxoban now prescribed over warfarin as lower risk of bleeding)
• If anticoagulation cannot be used (due to high risk of bleeding) - can use IVC filter to filter any thrombi/emboli propagating towards lungs/heart
- temporary until collateral vessels are formed

20
Q

Heparin

A
  • Stops thrombus propagation in the pulmonary arteries and at the embolic source
  • Does not lyse the embolus/thrombus itself
  • Reduces frequency of further pulmonary embolism
21
Q

Heparin-induced thrombocytopenia

A
  • Body produces antibodies (platelet factor 4-heparin antibodies) to a portion of heparin
  • Also recognise heparin-platelet complexes
  • Binding of antibodies to platelets activates them, causing platelet clumps that lead to thrombi
  • Low platelet count, but paradoxically increased risk of thrombosis
  • Similar mechanism to AZ Covid-19 vaccine induced thrombocytopenia
  • Treatment = immediate cessation of heparin
22
Q

Upper extremity DVT

A

• Acute thrombosis of a brachial, axial, or subclavian vein that may be caused by:
• Effort-induced thrombosis, triggered by repetitive
strenuous activity of the upper extremities (e.g., weight-lifting)
• Thoracic outlet syndrome; or Presence of a foreign object in veins (e.g., central venous catheter, pacemaker lead)
• A rare blood-based thrombosis that may also lead to PE

23
Q

Prevention of DVT/PE

A

• Outpatient - address risk factors
- obese woman may not be recommended to go on OCP or have HRT
• Inpatient
- DVT prophylaxis e.g. early mobilisation post-surgery/long flight
- Post-operative anticoagulation along with LMW heparin

24
Q

Cerebral air emboli

A
  • Usually iatrogenic (due to treatment/drugs) occurring especially in ICU patients
  • Air entry through central venous cannula, pulmonary artery catheters or haemodialysis catheters
  • Shows up as black regions between sulci/gyri of brain in CT scan
  • After some time, the air may dissipate and leave, but may cause infarct to affected region

Respiratory (4 decks)

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