KCP: Bleeding and Clotting Flashcards
How does a normal platelet plug form?
In normal blood flow platelets don’t adhere to the endothelial cells. However when cut platelets come into contact with the collagen in the sub endothelium to which they readily bind to VWF (von willhiem factor) via GBP1.
Once bound they become activated releasing their content granules ADP and thromboxane A2 which aggregate surrounding platelets.
Particullarly thromboxane A2 which causes the expression GP2b/3a which goes form bent to straight (like a flower).
This can now bind to fibrinogen in the blood which binds to the GP2b/3a on other platelets causeing them to become sticky.
Eventually this fibrinogen is converted to fibrin which is secondary hemostasis
What is the definition of primary hemostasis?
Where platelets from a plug
What is the definition of hemostasis?
Prevention of blood loss
What is the definition of secondary hemostasis?
Coagulation
Platelet plug memonic
A 62 year old man has five days of a swollen painful left leg. He has had three months of cough with occasional haemoptysis. He has hypertension and takes amlodipine. He is an ex-smoker.
His whole left leg is swollen including the thigh. He has oedema of the left leg. His left calf is 38 cm in diameter, his right calf is 30 cm in diameter.
What investigation would you do next?
What may have predisposed to deep vein thrombosis?
Odema, pain and swelling in one leg is sign of DVT.
Using a calculator he gets a Well’s score of 3
Well’s 0 or 1: do a D-dimer, if positive doppler ultrasound
Well’s 2 or more: do a doppler ultrasound on leg to test flow
Predisposed:
Haemoptysis: Coughing up blood, suggests cancer - damage to vessel walls
Hypertension: Can cause damage to vessel walls
What is DVT (deep vein thrombosis)
DVT (deep vein thrombosis) is a blood clot in a vein, usually in the leg.
What is factor Xa?
It is an enzyme involved in the intrinsic pathway (within the vien) coagulation cascade (converting of fribinsin to fibrin)
How is DVT treated?
Low molecular weight heparin e.g. dalteparin followed by factor Xa inhibitors or warfarin
A 72 year old woman has two days of breathlessness. She had a left total hip replacement three weeks ago.
Her pulse is 120 bpm, blood pressure 102/70 mmHg and oxygen saturation 88% breathing air. Her chest is clear. Her left leg appears normal
She has a normal chest X-ray
How would you investigate further?
Use Well’s calculator for PE
Score: 6
If < 4: D-dimer
If > 4: CTPA (ct pulmonary angiogram)
Possibly prevoked by hospital stay? If so treat for 3 months
If unprovoked they have a problem with their clotting and it would be long term treatment
Pulmonary embolus-presentation?
It’s hard to spot but…
- Breathlessness (most common)
- Pleuritic chest pain
- Cough
- Calf or leg swelling
- Tachycardia, including AF
- Tachypnoea
- Crackles or reduced breath sounds in around 1/5th
- Elevated JVP
How is pulmonary embolus treated?
Same as DVT.
Low molecular weight heparin e.g. dalteparin followed by factor Xa inhibitors or warfarin
Why is venothromboembolism risk increased in hospital patients?
What can be done to minimise this risk?
- Too much lying down
- Dehydration
- Underlying condition bringing them to hospital that puts them at risk e.g. cancer/ inflammation
How to prevent in hospital:
- Give Anti-embolus stockings.
- Get walking
- Keep hydrated
- If high risk preventative warferin
Blood test for DVT or PE?
Can test for D-dimer. D-dimer is a by-product of the blood clotting and break-down process that can be measured via analysis of a blood sample. D-dimer is released when a blood clot begins to break down.
Imaging Investigation for DVT?
Proximal leg vein ultrasound
Imaging investigation for PE?
A CT pulmonary angiogram (or CTPA) is a CT scan that looks for blood clots in the lungs
Diseases which increase risk of DVT and PE?
Any heart disease or lung disease amplifies effects of a small DVT or PE as heart/lungs don’t work as well.
IBS/ Chron’s increase risk of DVT.
Extrinsic vs intrinsic clotting
Extrinsic: From an injury outside a blood vessel
Intrinsic: Injury to the endothelium inside the vessel
What is Virchow’s triad of clotting?
It is the main factors to contribute to clotting
What does deep vein thrombosis look like?
Painfull swelling of leg due to inability of blood to return to heart
However 80% are clinically silent
What is thrombophilia?
An abnormal tendency to develop blood clots.
Who should you test for thrombophilia?
Anyone who has unusual clotting e.g.
- Venous thrombosis < 45yo
- Family history of unprovoked venous thrombosis
- Recurrent venous thrombosis
- Venous thrombosis at an unusual site
- Combination of venous and arterial thrombosis
When might you use unfractionated heparin over low molecular weight heparin?
With UH the dosing is unreliable and it requires monitoring, it also has more side effect so in most case LMWH is preferable.
However if there is a high risk of bleeding use UH as it is reverible so if bleeding gets out of control you can reverse it
