Pulmonary Embolism Flashcards
Define PE
Obstruction of one or more pulmonary arteries by a solid, liquid or gaseous mass
Epidemiology PE
- Accounts for many deaths per year
- Incidence increases with age
- M > F
- Deaths due to VT = 34% attributable to sudden fatal PE
- Increasing incidence of PE
Broad categories of PE aetiologies
- Deep vein thrombosis (most common)
- Fat embolism
- Air embolism
- Amniotic fluid embolism
- Tissue embolism
Risk factors for a DVT
- Obesity
- Hypomobility
- Malignancy
- Pregnancy
- Dehydration
- OCP
- Previous DVT
When are fat embolisms most common
During major surgical interventions
Pathophysiology behind PE
- Thrombus formation that embolises to pulmonary arteries via the IVC (rarely SVC)
- Leads to a partial or complete blockage of the pulmonary arteries
- Thrombi rarely develop de novo in the pulmonary vasculature
Problems associated with lung and arterial obstruction
- Infarction and inflammation
- Impaired gas exchange
- Cardiac compromise
Describe what happens when infarction and inflammation result from PE
- Occurs in lung and pleura
- Pleuritic chest pain and haemoptysis
- Surfactant dysfunction leads to atelectasis and decreased paO2
- Leads to respiratory alkalosis and hypocapnia (as respiratory drive triggered)
Describe what happens with impaired gas exchange in PE
- Ventilation-perfusion mismatch
- Arterial hypoxaemia
Describe what happens with cardiac compromise with PE
- Elevated pulmonary artery pressure leads to right ventricular pressure overload
- Forward failure
- Decreased cardiac output
- Hypotension and tachycardia
Clinical features of PE
- Acute onset of symptoms
- Often triggered by a specific event (waking up, exercise etc)
- Dyspnoea
- Tachypnoea
- Sudden chest pain - worse on inspiration
- Cough and haemoptysis
- Dullness on percussion
- Decreased breath sounds
- Tachycardia
- Hypotension
- Jugular vein distension
- Low-grade fever
- Syncope/shock/circulatory collapse with major PE
- Possible symptoms of DVT
DDx for PE
- Unstable angina
- NSTEMI/STEMI
- CAP
- CHF
- Acute bronchitis
- Acute exacerbation of COPD or asthma
- Pericarditis
What does Wells criteria measure
- Score in stable patients - access probability of PE
also a Wells criteria for DVT
7 components of Wells
- Clinical signs of DVT
- Alternative diagnosis less likely than a PE
- Previous PE or DVT
- HR >100bpm
- Surgery or immobilisation within 4 weeks
- Haemoptysis
- Active malignancy (treating/palliative/diagnosed <6months ago)
Score for a high chance of PE
> 4
Score for a low change of PE
<=4
If patient is haemodynamically stable (SBP >90) and at high risk of PE, what is initial management on presentation
- CTA/CTPA
- If contraindicated - immediate anticoagulant - unfractionated heparin
If a patient is too unstable for CTA - what is first line management
- Bedside echocardiogram - look for RV enlargement and visualise clot)
- Done prior to empiric thrombolysis
Management in someone at low probability of PE
- Measure D-dimer, ABG and CXR
Positive D-dimer
- Not diagnostic for PE
- Progress to CTA
Negative D-dimer
- High probability no PE
- DDx
What is the D-dimer test
- D-dimers are fibrin degradation products detected in the blood after thrombus resolution via fibrinolysis
Normal D-dimer level
<500ng/mL
D-dimer test has high…..
Sensitivity and NPV = negative test can rule our PE
D-dimer test has low….
Specificity = poor confirmatory test
ABG and PE
Respiratory acidosis - decreased pO2, pCO2 and increased pH
What is a CTPA
CT pulmonary angiogram - contrast enhanced imaging of pulmonary arteries
Positives about CTPA
- High sensitivity and specificity
- Visible intraluminal filling defects
Why is a CXR done on PE management
- Rule OUT other cuases
- Check for atelectasis
- Signs of PE on a CXR are rare
Why is an echo done on PE management
- Detect RA pressure signs
Why is a VQ test done on PE management
- Use as an alternative to CTPA in patients with severe renal insufficiency or contrast allergy
Acute general treatment for suspected PE
- Seated at 45 degrees
- O2 supplementation and intubation
- IV fluids and and vasopressors if hypotensive
- Analgesics
PE and empiric anticoagulation - contraindication
Bleeding risk
Empiric anticoagulation - 0-10 days
- LMWH (use unfractionated if renally compromised)
Empiric anticoagulation - 3-6 months
- Long term treatment and prophylaxis
- Warfarin, LMWH, direct oral anticoagulants
Recanalisation and PE
- Thrombolytic therapy = massive PE or haemodynamically unstable = use tPA (fibrinolysis)
- Embolectomy = last resort = surgical or catheter based thrombus removal
Interventional surgery prevention for PE
IVC filter
- Mechanical device implanted into IVC
Medication prevention of PE
DVT prophylaxis
PE complications
- High risk of recurrence without treatment (5-10%)
- RV failure
- Atelectasis (20%)
- Pulmonary effusion
- Pulmonary infarction (10%)
- Pneumonia (from infarction)
