35.DVDT and Pulmonary Embolism (venous thromboembolism) Flashcards
What is the prevalence rate of venous thromboembolism in a population?
1 in 1000 per year
What is the fatality/death rate in venous thromboembolism patients?
1-5%
When is the biggest risk of venous thromboembolism?
- postoperative risk
- can be up to 6 week after discharge
Define thrombus.
- blood clot formed in situ (stationary/in one place) within a vascular system of the body of impeding blood flow
- causes vascular obstruction
- remain attached to its place of origin (unlike embolism)
Define thromboembolism
movement of clot along a blood vessel to other body regions
Define embolism.
- obstruction of an artery (can be clot, air bubble or any foreign material) that becomes stuck while travelling through the blood stream
What 2 things balance haemostasis?
- bleeding
2. thrombosis
What are 3 components of the Virchow’s Triad which contribute to thrombosis?
- stasis
- hypercoagulability
- vessel damage
What are 2 factors which can affect blood stasis?
- bed rest (e.g. post op)
2. travel
What are 2 factors which can affect hypercoagulabiltiy?
- pregnancy
2. trauma/injury
What can affect vessel damage?
atherosclerosis
What are 2 main examples of venous thromboembolism?
- limb deep vein thrombosis
2. pulmonary embolism
What are conditions similar to venous thromboembolism? (3)
- visceral venous thrombosis
- intracranial thrombosis
- superficial thrombophlebitis
What is visceral venous thrombosis?
Thrombosis of splenic, hepatic, mesenteric, portal, renal, ovarian veins
What is intracranial thrombosis?
-thrombosis and obstruction in the cerebral veins
What is superficial thrombophlebitis?
- vein inflammation which is due to a blood clot
- thrombus develops in the vein which close to the surface of the skin
- can occur anywhere but more likely in lower body regions
- most superficial veins that develop thrombosis also develop phlebitis
What is venous thrombus mainly made up of? (2)
- fibrin
- red cells
“red thrombus”
What causes a venous thrombus? (2)
- results from back pressure
- due to stasis and hypercoagulability
Why is atherosclerosis not common in veins which is why vessel damage isn’t the main cause of venous thrombus?
Because arteries have blood at much higher pressure than veins which makes them more susceptible to vessel damage and plaque formation which results from high BP that causes endothelial damage (original insult to start cascade for plaque formation).
This is LESS common in veins
What is arterial thrombus mainly made up of? (2)
- fibrin
- platelets
“white clot”
What are arterial thrombi principally secondary to? (what causes them?)
atherosclerosis (due to vessel damage)
What do arterial thrombi result in? (2)
- ischaemia
2. infarction
Can DVT be clinically silent?
yes
What are the common symptoms and signs of DVT? (7)
- unilateral limb swelling
- persisting discomfort
- calf tenderness
- warmth
- redness; erythema
- mild fever
- pitying oedema
What are common symptoms and signs of pulmonary embolism? (5)
- pleuritic chest pain
- breathlessness; dyspnoea
- haemoptysis (blood in sputum)
- tachycardia
- pleural rub on auscultation
What are common symptoms and signs of a massive pulmonary embolism? (6)
- severe dyspnoea of sudden onset
- blue lips and tongue (cyanosis)
- tachycardia
- low blood presure
- raised JVP
- altered heart sounds
MAY CAUSE SUDDEN DEATH
What is the biggest potential long-term consequence of DVT?
Post-phlebetic syndrome; due to venous inflammation and damage to venous valves
What are signs of post-phlebetic syndrome? (4)
- swelling and oedema
- discomfort (itching/tingling)
- pigmentation (reddish/brownish)
- ulceration
What is the biggest potential long term consequence of pulmonary embolism?
pulmonary hypertension
What 2 component of the Virchow’s Triad are the biggest risk factors for venous thrombosis?
- Stasis
2. Hypercoagulability
What are risk factors for venous thrombosis? (9)
- increasing age
- tissue trauma
- immobility
- obesity
- smoking
- some systemic disease e.g. cancer
- inheritance
- pregnancy
- exogenous oestrogen
Define heritable thrombophilia.
An inherited predispostion to venous thrombosis
What is the most common and prevalent hertiable thrombophillia?
Factor V Leiden
What % of Caucasians suffer from Factor V Leiden? (heritable thrombophillia)
5%
What does heritable thrombophilia condition like Factor V Leiden increase the risk of?
venous thromboembolism
What increases risk of Factor V Leiden (clotting disorder) which leads to venous thromboembolism?
oral contraceptive
Who does travel affect in terms of increasing risk of venous thromboembolism? (5)
- short
- tall
- overweight /obese
- women on the contraceptive pill
- window seats people
What investigations need to be done to diagnose DVT? (5)
- clinical assessment
- Blood test: D dimer (measures substance that is released when clot broken down)
- ultrasound (for propagating DVTs)
- thrombophilia test (esp. if in family history or no predisposing factors)
- check underlying malignancy
What imaging techniques can be used as investigation for DVT? (1)
-compression ultrasound (to check for malignancies or for propagating DVTs)
What features are on the clinical probability assessment used to establish if patient is at risk of a DVT?
- active cancer
- paralysis
- bed>3 days/ surgery within 4 weeks
- tender veins
- entire leg and calf swelling>3cm
- pitting oedema
- collateral veins
- alternative diagnosis likely (-2 points)
What is a low probability score for clinical probability assessment for DVT?
0 or less (~3% risk)
What is a moderate probability score for clinical probability assessment for DVT?
1 or 2 (~17% risk)
What is a high probability score for clinical probability assessment for DVT?
3 or more (~75% risk)
What investigations are done to diagnose pulmonary embolism? (7)
- clinical assessment
- D dimer (blood)
- CT pulmonary angiogram
- Isotope ventilation/perfusion scan
- chest x ray
- full blood count: Urea+electrolytes, arterial blood gases (ABG), baseline clotting
- ECG
What preventive measure of venous thromboembolism can be undertaken in a hospital?
- early mobilisation
- anti-embolism stockings
- other physical methods
- daily injections of low molecular weight heparin (anticoagulant)
How do antiembolism stockings help reduce risk of DVT?
Promote maximal femoral blood flow velocty of 139% baseline
What pressures do antiembolism stockings in the 3 leg regions?
- 18mmHg at the ankle
2;. 14mmHg at the mid-calf - 8mmHg at the upper thigh
When are graduated compression stockings used? (6)
- prevention of DVT
- chronic venous insufficiency
- varicose veins
- oedema
- lymphoedema
- prevention of post-phlebetic syndrome
