The Coagulation Panel Flashcards
What is Haemostasis?
Process to fix a break in blood vessel wall
How are coagulation factors involved in secondary haemostasis measured?
- Blood contained in citrate tube
- Spin blood, set off the coagulation cascade
- Visually look for a clot
- Automated system detects light penetration (as fibrinogen becomes fibrin and strands start to crosslink the mixture gets cloudy and machine detects this)
What is PT?
Prothrombin time measured in seconds
What is APTT?
activated partial thromboplastin time measured in seconds
What is Fibrinogen?
beware derived versus measured, measured in g/L
What is INR?
Internationally standardised ratio based on the PT, technically only valid for warfarin
What are results affected by?
sampling issues and other interferences in the test tube
What are DOACs?
Direct- acting oral anticoagulants
Rivaroxaban/ apixaban
Where does DOAC act?
Factor X (prevents from activating)
IIa
What DOACs affect factor X?
apixaban
rivaroxaban
What DOACs act on IIa?
dabigatran
What is the benefit of DOACs?
- Don’t need routine monitoring of levels
- Standard dose
- Act on factor X prevents it from becoming activated
- Means no prothrombin to thrombin which means no fibrinogen= prevents a clot
- Act on fac 2 directly
How DOACs affect coag panel tests?
Variable non- linear impact of PT & APTT
What clinical scenarios are DOACs used?
Blood clots
What does Warfarin inhibit?
Inhibits activity of vitamin K
Vitamin K dependent clotting factors= inhibited
What vitamin K dependent clotting factors are there?
IX, VII, X, II= inhibited
How does Warfarin affect the coag panel?
- Warfarin affects both PT & APTT
- INR is standardised way of reporting PT
- Use INR to adjust warfarin dosing
What is PT sensitive to?
- PT is particularly sensitive to the clotting factors affected by warfarin so can be used to accurately monitor the degree of warfarin- induced anticoagulation
What clinical scenarios is warfarin used for?
Blood clots
What are Heparins?
- Naturally occurring sulphated glycosaminoglycans isolated from animal tissue, most commonly porcine intestine
What do heparins do?
- Indirectly inhibit blood coagulation, by potentiating the anticoagulant effect of antithrombin x2000
- Accelerates the inactivation of thrombin (IIa) & factor Xa
What is the unfractionated heparin?
- Can bind to both antithrombin (AT) & thrombin (IIa)
- Given intravenously
- Requires a loading dose before continuous infusion
- Requires careful monitoring
What is low molecular weight heparin?
- Smaller molecular size
- Binds antithrombin and potentiates its inhibitory effect on Xa
- Cannot bind thrombin (IIa)
- Subcut injection
- More predictable pharmacokinetics
- Weight dependent dosing
How does Heparin affect coag panel tests?
- UFH affects APTT
- Adjust dosing using APTT ratio
- LMWH also affects APTT but less sensitively, depends on chain length of the LMWH, longer chain= more APTT prolongation
What is an example of a Thrombolytic?
tPA
What are the uses of thrombolytics?
Thrombolysis= “clot buster” medicine
Systemic versus catheter- directed thrombolysis
What clinical cases are Thrombolytics used for?
- Massive PE with haemodynamic instability
- Acute ischaemic stroke
- Blocked CVC line
- Acute limb ischaemia
Do antiplatelets affect coag panel tests?
NO
What are the uses of antiplatelets?
- Primary prevention- high cardiovascular risk score
- Secondary prevention- after MI, stroke, PCI/ stenting, PVD, arterial thrombosis
- No effect on clotting cascade
- Involved in primary haemostasis
- stop platelets being so sticky
What is Haemophilia A?
- X- linked
- Recessive
- Mainly affects males
- Problem with factor 8 (severe end= no factor 8)
What is Haemophilia B?
- Affects gene which makes factor 9
- Recessive
- X linked
- Rarer
What are the symptoms of Haemophilia?
Both can cause huge pregnancy complications, huge risk of bleeding
Haemorrhages, excessive brusing
What is the treatment for Haemophilia?
Preventative drugs which stop bleeding
What does Von willebrand’s disease affect?
- Important in primary and secondary haemostasis
How does vwb affect primary haemostasis?
Binds platelets
Binds exposed endothelium
Forms adhesive bridge between vascular endothelium & platelets
Forms platelet plug
How does VWD affect secondary haemostasis?
As it is a carrier for FVIII in the blood (otherwise FVIII would be rapidly degraded in the circulation)
What different types of vWB disease are there?
Quantitive (low levels)
Qualitative (abnormal function)
What can happen to APTT in VWB?
APTT can be prolonged in some forms of more severe VWB due to the resulting low FVIII levels
What are symptoms of VWD?
Spectrum of severity
Often mucosal bleeding
What is DIC?
Disseminated intravascular coagulopathy
What happens in DIC?
-Dysregulation of normal process of haemostasis
-Balance of clotting versus bleeding (fibrinolytic) tendency
- Generation and deposition of fibrin
What are the 2 stages of DIC?
Overactive clotting followed by bleeding
- Initially prothrombotic, as things continue the clotting factors & platelets get used up leading to bleeding symptoms
How do you treat DIC?
Identify underlying cause:
- Severe sepsis
- Malignancies
- Obstetric complications
- Trauma
- Severe burns
- Liver failure
- Pancreatitis
- CAPS
- heat stroke/ hyperthermia
Blood product support as required
