Pulmonary Embolism Flashcards
(30 cards)
What is a pulmonary embolism?
When a blood clot in the pulmonary arterial vasculature develops, usually from an underlying deep vein thrombosis (DVT) of the lower limbs.
How is a pulmonary embolism formed?
(DVT) that developed in the legs and travelled (embolised) through the venous system and the right side of the heart to the pulmonary arteries in the lungs.
Once they are in the pulmonary arteries they block the blood flow to the lung tissue and create strain on the right side of the heart.
What are DVTs and PEs collectively known as?
DVTs and PEs are collectively known as venous thromboembolism (VTE).
Risk factors
Immobility
Recent surgery
Long haul flights
Pregnancy
Hormone therapy with oestrogen
Malignancy
Polycythaemia
Systemic lupus erythematosus
Thrombophilia
Signs and symptoms
Shortness of breath
Cough with or without blood (haemoptysis)
Pleuritic chest pain
Hypoxia
Tachycardia
Raised respiratory rate
Low grade fever
Haemodynamic instability causing hypotension
A massive pulmonary embolism may present with the above and syncope/shock.
A massive pulmonary embolism may present with hypotension, cyanosis, and signs of right heart strain (such as a raised JVP, parasternal heave, and loud P2).
It is important to look for signs of a concomitant deep vein thrombosis (a unilaterally swollen, tender calf).
ECG changes
Normal or sinus tachycardia.
In a massive PE there may be evidence of right-heart strain (with P pulmonale, right axis deviation, right bundle branch block, and non-specific ST/T wave changes).
The classic S1Q3T3 (deep S waves in lead I, pathological Q waves in lead III, and inverted T waves in lead III) is relatively uncommon (<20% of patients).
Prophylaxis
Every patient admitted to hospital should be assessed for their risk of venous thromboembolism (VTE).
If they at increased risk of VTE they should receive prophylaxis with a low molecular weight heparin such as enoxaparin unless contraindicated.
Contraindications include active bleeding or existing anticoagulation with warfarin or a NOAC.
Anti-embolic compression stockings are also used unless contraindicated.
The main contraindication for compression stockings is significant peripheral arterial disease.
ABG in PE
Normal or show a type 1 respiratory failure (hypoxia without hypercapnia) and/or a respiratory alkalosis (due to hyperventilation secondary to hypoxia).
Remember the baseline tests such as FBC (the patient may be anaemic if the PE has caused haemoptysis), CRP may be raised, U&E (to assess renal function before CTPA), clotting function (important if the patient is to be started on LMWH/Warfarin).
Base line bloods in PE
FBC (the patient may be anaemic if the PE has caused haemoptysis)
CRP may be raised
U&E (to assess renal function before CTPA)
Clotting function (important if the patient is to be started on LMWH/Warfarin).
D-dimer bloods in PE
Highly non-specific but has a 95% negative predictive value i.e. it is useful in ruling out a PE if negative).
What is the Well’s score used for?
Risk of a patient presenting with symptoms actually having a DVT or pulmonary embolism.
Why would 3 points be appointed in Well’s score?
Clinical signs and symptoms of a deep vein thrombosis (DVT)
If no alternative diagnosis is more likely than a PE
Why would 1.5 points be appointed in Well’s score?
Tachycardia (heart rate >100 beats/minute)
If the patient has been immobile for more than 3 days or has had major surgery within the last month
If the patient has had a previous PE or DVT
Why would 1 point be appointed in Well’s score?
If the patient presents with haemoptysis
If there is an active malignancy
What should be done if the Well’s score is 4 or less?
If the Well’s score is 4 or less the D-dimer should be measured.
A low D-dimer excludes a PE. A raised D-dimer is an indication for diagnostic imaging (by CTPA or V/Q scan).
What should be done if the Well’s score is more than 4?
If the Well’s score is more than 4 further diagnostic imaging is required. Low-molecular weight heparin is typically administered in the interim if the clinical suspicion of a PE is high (and should certainly be administered if there is delay in performing the CTPA).
Medical management
The initial recommended treatment is apixaban or rivaroxaban.
Low molecular weight heparin (LMWH) is an alternative where these are not suitable, or in antiphospholipid syndrome.
It should be started immediately before confirming the diagnosis in patients where DVT or PE is suspected and there is a delay in getting the scan.
Examples are enoxaparin and dalteparin.
How long should patients be on anticoagulants?
3 months if there is an obvious reversible cause (then review)
Beyond 3 months if the cause is unclear, there is recurrent VTE or there is an irreversible underlying cause such as thrombophilia.
6 months in active cancer (then review)
What is INR?
A diagnostic test relating to how long it takes for blood to clot
If INR is high, it means blood does not clot quickly enough putting patient at risk of bleeding
What are options for long term anticoagulants?
The options for long term anticoagulation in VTE are warfarin, a DOAC or LMWH.
What should be done when switching to warfarin?
The target INR for warfarin is 2-3. When switching to warfarin continue LMWH for 5 days or the INR is 2-3 for 24 hours on warfarin (whichever is longer).
What is the recurrence of a VTE in a patient already on warfarin?
Recurrence of a VTE in a patient already on warfarin requires an increase in the target INR (to 3-4).
What are DOAC’s?
Direct oral anti coagulants
directly inhibit specific proteins within the coagulation cascade
How does Warfarin work?
Warfarin competitively inhibits the vitamin K epoxide reductase complex 1 (VKORC1), an essential enzyme for activating the vitamin K available in the body.
Vitamin K is an essential cofactor for the synthesis of all of these vitamin K-dependent clotting factors.
