Embolism Flashcards
What is an embolism?
An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel
What are the different types of emboli?
- Arterial
- Venous
- Paradoxical
- Direction
What is a paradoxical embolism?
An embolus from the veins crosses to the arterial blood system
The most common such abnormality is patent foramen ovale, occurring in about 25% of the adult population
What is an pulmonary embolism?
blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream
What are symptoms of a pulmonary embolism?
SoB Chest pain Pleuritic pain DVT Coughing blood
What are signs of a pulmonary embolism
Hypoxia Tachypnoea, tachycardia Mild fever Syncope Hypotension Obstructive shock
What are risk factors for developing a pulmonary embolism?
Cancer Prolonged bed rest Smoking Stroke Genetic conditions Estrogen-based medication Pregnancy Obesity Post surgery
What causes pulmonary embolisms?
About 90% of emboli are from proximal leg deep vein thrombosis (DVTs) or pelvic vein thromboses
What is Virchow’s triad?
Virchow’s triad or the triad of Virchow describes the three broad categories of factors that are thought to contribute to thrombosis.
- Hypercoagulability
- Hemodynamic changes
- Endothelial injury/dysfunction
What is the Well’s score?
Likelihood of a pulmonary embolism
What factors are part of the Well’s score?
Clinically suspected DVT (4 points)
Alternative diagnosis less likely than PE. (3 points)
Tachycardia > 100 (1.5 points)
Immobilisation for more than three days or surgery in the previous four weeks. (1.5 points)
History of DVT or PE. (1.5 points)
Haemoptysis. (1 points)
Malignancy (1 points)
What Well’s score indicates likely PE?
4 points or fewer = PE unlikely.
More than 4 points = PE likely.
What investigations would you do for suspected PE?
Saturation, FBC, baseline clotting screen ECG CXR ABG D-dimer
What are specific test would you use to image the pulmonary vasculature in patients with suspected PE
CT pulmonary angiogram (CTPA)
A ventilation/perfusion lung scan
What does D-dimer tell you?
fibrin D-dimer is a degradation product of cross-linked fibrin
The concentration increases in patients with acute VTE and provides a very sensitive test to exclude acute DVT or PE
What is the prognosis for pulmonary embolisms?
Less than 5 to 10% of symptomatic PEs are fatal within the first hour of symptoms
What is the prognosis for pulmonary embolisms?
Less than 5 to 10% of symptomatic PEs are fatal within the first hour of symptoms
What type of embolism causes a petechial rash?
Fat embolism
What feature distinguishes a fast embolism from other embolisms?
Petechial rash
What causes fat embolisms?
Bone fractures (especially femur)
Pancreatitis
Bome marrow transplantation
Liposuction
How would you manage a pulmonary embolism?
Intravenous alteplase or UFH if hypotensive
If patient normotensive, then give LMWH
What is the diagnosis algorithm for a suspected PE?
- Determine 2 level PE Wells score
2A: Wells > 4 –> IMMEDIATE CTPA or anticoagulants
- CTPA positive: diagnose PE and offer treatment
CTPA negative: DVT suspected, vein ultrasound
2B. Wells < 4
- Quantitative D-dimer
After a DVT or PE, what medication would you give for secondary prevention?
Offer apixaban or rivaroxaban in otherwise healthy patients
- LMWH if they’re not suitable
In active cancer, consider DOAC
What is the diagnosis algorithm for a suspected DVT?
- Determine 2 level PE Wells score
2A. Wells > 4 –> proximal vein ultrasound within 4 hours OR D-dimer
- Scan neg: D-dimer, offer second scan
2B. Wells < 4 –> D-dimer
After a DVT or PE, how long would you give medication for secondary prevention
At least 3 months
What is the advantage of LMWH vs heparin?
better bioavailability and longer half-life, simplified dosing, predictable anticoagulant response
What is the mechanism of action for heparin?
activating antithrombin
What do you use LMWH for?
Used in the prevention of blood clots and treatment of venous thromboembolism
When would you give Antiplase?
Used to treat acute ischemic stroke, acute ST-elevation myocardial infarction (a type of heart attack), pulmonary embolism associated with low blood pressure
After a DVT or PE, what medication would you give for secondary prevention in people with renal failure?
LMWH
UFH
In a suspected PE or VTE, what medication would you give while you wait for scans or tests to confirm the diagnosis?
Offer apixaban or rivaroxaban
What do you need to measure before prescribing apixaban or rivaroxaban?
FBC, renal function and hepatic function!
What is the mechanism of action of apixaban?
Apixaban is a direct inhibitor of activated factor X (factor Xa).
What is the mechanism of action of rivaroxaban?
Rivaroxaban is a direct inhibitor of activated factor X (factor Xa).
What is the correct dose of rivaroxaban for treatment PE or DVT?
Initially 15 mg twice daily for 21 days, then maintenance 20 mg once daily
What is the correct dose of apixaban for treatment PE or DVT?
Initially 10 mg twice daily for 7 days, then maintenance 5 mg twice daily.
What is the correct dose of rivaroxaban as prophylaxis for DVT?
10 mg once daily for 2 weeks, to be started 6–10 hours after surgery.
What is the correct dose of apixaban as prophylaxis for DVT?
2.5 mg twice daily for 10–14 days, to be started 12–24 hours after surgery.
What are intrinsic risk factors for DVT?
A history of DVT. Cancer (known or undiagnosed). Age over 60 years. Being overweight or obese. Male sex. Heart failure. Smoking
What are temporary risk factors for DVT?
Recent major surgery. Recent hospitilisation. Recent trauma. Chemotherapy. Significant immobility
When would you suspect DVT?
Unilateral localised pain
Tenderness
Oedema, redness, warmth
What happens when blood is exposed to the subendothelial space after injury to a vessel?
- Changes in platelets
- Exposure of subendothelial tissue factor to plasma factor VII, which ultimately leads to cross-linked fibrin formation
What factors does clotting factor VII activate?
IX and X
What does clotting factor X do?
Activates prothrombin to thrombin
Factor X acts with co-factor FVa
What does thrombin do?
Activates fibrinogen into fibrin, which which strengthens the platelet plug
Also activates factor XIII
What enzyme breaks down blood clots?
Plasmin
