Pulmonary Embolism Flashcards
What is a pulmonary embolism (PE)?
obstruction to the pulmonary arterial system by 1 or more emboli, causing severe respiratory dysfunction.
What is an emboli?
something that travels through the bloodstream, lodges into a blood vessel and blocks it?
Types of emboli that can cause a PE? (6)
- thrombosis (most common)
- fat (following long bone fractures/orthopaedic surgery)
- air (from surgery or another communication between environment and venous system)
- amniotic fluid
- sepsis (e.g. tricuspid valve endocarditis in IV drug use, receipt of transplanted organ etc.)
- foreign bodies (e.g. from IV drug use, broken catheters, vena cava filters etc.)
Types of PE’s? (2)
- provoked - antecedent within 3 months and transient risk factors that can be removed, reducing the risk of reoccurrence
- unprovoked - occurs in the absence of risk factors or the risk factors are persistent/not easily correctable (e.g. active cancer or thrombophillia)
What is venous thromboembolism (VTE)?
Encompasses both PE and DVT
What is a deep vein thrombosis (DVT)?
The formation of a thrombosis (blood clot) in a deep vein (e.g. lower limbs, upper limbs, splanchnic or cerebral veins)
Pathophysiology of PE?
- decrease in perfusion but ventilation remains the same causing an increase in dead space and less gas exchange
- Therefore lung tissue may infarct (but may not as bronchial circulation and airways continue to supply oxygen)
- There is an decrease in the cross sectional area of the pulmonary arterial bed = increased pulmonary arterial pressure
- After several hours, alveolar collapse occurs
How does right ventricular failure occur from a PE?
Large and multiple emboli causes an abrupt increase in the pulmonary arterial pressure. The increase in afterload cannot be matched by the right ventricle.
What are the major risk factors for PE? (7)
- significant immobility
- late stage of pregnancy/peripurium
- active cancer
- previous VTE
- DVT
- recent surgery
- lower limb trauma/fracture
What are the minor risk factors for PE? (8)
- increasing age (>60 years)
- HRT and combined contraceptive pills
- pregnancy
- long haul flights
- obesity (BMI > 30 kg/m2)
- varicose veins
- known thrombophillia
- significant co-morbidities (heart disease, metabolic, endocrine, neurological, respiratory, inflammatory)
Signs and symptoms of PE (7)
- dyspnoea
- cough and haemoptysis
- retrosternal pleuritic chest pain
- elevated JVP
- syncope/collapse/dizziness/sudden death (severe)
- sats: high HR and high RR, low bp, pyrexia, low PaO2
- TR murmur, gallop heart rhythm, pleuritic rub
Differentials for PE (6 categories)
- cardiac: ACS/MI, pericarditis, acute CHF, dissection/rupturing aortic aneurysm
- respiratory: pneumothorax, pneumonia, acute bronchitis, exacerbation of COPD, asthma or chronic lung disease
- musculoskeletal pain
- GORD
- panic disorder
- cause of collapse: cardiac (OH, syncope, arrhythmia), neurological seizures
Criteria to use when clinical suspicion of PE is low?
PE rule-out criteria (PERC) - determines if further investigation is required. All variables must receive a “no” to be negative.
Criteria to use when PE is suspected?
Two level PE Wells Score - estimates the clinical probability of PE
What score must they have on the PE Wells Score to make PE likely? What test will they require?
> 4 = high probability of PE. Arrange CTPA.
< 4 = low probability of PE. Arrange d-dimer, if test is positive arrange CTPA.
