The coagulation system Flashcards
What is Virchow’s Triad?
Stasis of blood flow
Hyper coagulability - components of blood
Vascular Injury - blood vessels
Describe stasis
Immobility - post op state, debility, coma --> ICU or medical ward - Economy class syndrome Pressure - Catheter (Central line blockage) or tumour obstruction Increased viscosity - Polycythemia - Dehydration - EPO
Blood hyper coagulability (mainly venous thrombosis)
Increased procoagulants (factor VIII) Decrease in inhibitors
what is a VT (venous thromboembolism)
DVT or PE = 2 potential presentations of the same disease
PE slightly less common than a DVT
Signs and symptoms of 1.DVT and 2.PE
DVT: - Leg swelling - Leg pain - Oedema PE - Shortness of breath - Chest pain - Tachycardia -Tachypnoea All these symptoms are nonspecific and common making it hard to diagnose, use diagnostic algorithms (e.g. wells score) to be more accurate
What are D-dimers?
Breakdown products of fibrin
Positive in the 83-98% of DVT and PE (depending on method)
Also positive in patients without VTE - inflammation and surgery
Test not very accurate: high false negative and low true positive
Should be interpreted with a clinical score
When do you use the D-dimer testing when you’re suspicious that a patient has a DVT off the wells score
IF clinical score shows low probability of DVT
test for D-dimers
if negative then discharge
If positive send for scan
What is the diagnostic scan for DVT?
US!! doppler
3/4 of symptomatic DVT are proximal (popliteal and above) if untreated half will embolise to the lung
IF patient turns up with DVT what are some casual factors you should check for?
CANCER!!
e.g. if 60 yr old male has recent unexplained weight loss and iron deficiency then do colonoscopy
Classic symptom triad of PE
+ classic sings
Symptoms:
pleuritic pain
Shortness of breath
Haemoptysis
Signs:
Tachycardia
Tachypnoea
Hypoxia
Prognosis of a massive PE
Sudden death 15%
Mortality >50%
Hypotension
severe right heart pain due to back pressure from pulmonary arteries
What is thromboplilia
Tendency to develop thrombosis can be acquired or inherited or both Term usually applied to hereditary manifested as VTE multi hit theory
causes of VTE
30-40% spontaneous - about 50% of these have a hereditary factor which increases risk: thrombophilia Remainder provoked - surgery or trauma - immobility - hospitalisation - malignancy - HRT/OCP/pregnancy other e.g. myeoloproliferative diseases
Is travel immobility a huge risk factor for VTE?
No
OCP and obesity far worse
Inherited thrombophilia
Abnormal inhibitor function
- Resistance to activated protein C (Factor V Leiden)
Deficiency of inhibitors
- antithrombin, protein C or S deficiency
- RARE, also deficiency of these factors doesn’t affect the APTT (heparin, dibigitran and lupus anticoagulant do)
