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1/ 
Tweetorial;
The prothrombin time (PT) is designed to test coagulation factors of the extrinsic (VII) & common (II, V, X, fibrinogen) pathways
*Remember that the 'extrinsic' vs 'intrinsic' division of factors was never made to be a true representation of in vivo activity*
Tweetorial; The prothrombin time (PT) is designed to test coagulation factors of the extrinsic (VII) & common (II, V, X, fibrinogen) pathways
*Remember that the 'extrinsic' vs 'intrinsic' division of factors was never made to be a true representation of in vivo activity*
2/ In simple terms, you mix the patient plasma (platelets removed) with activators of the extrinsic pathway (tissue factor, phospholipid & calcium) and measure the time taken to form a clot
3/ 
levels of the factors above will lead to 
of the PT as it takes longer for a clot to form
The commonest reason for an isolatedPT is factor VII deficiency- this clotting factor has the shortest half-life and therefore is 'consumed' first in illness e.g sepsis/post-op
levels of the factors above will lead to of the PT as it takes longer for a clot to formThe commonest reason for an isolated
PT is factor VII deficiency- this clotting factor has the shortest half-life and therefore is 'consumed' first in illness e.g sepsis/post-op
4/ Other causes are vitamin K deficiency, use of warfarin and liver disease (acute or chronic). Use history and other tests to consider these possibilities first
Congenital factor VII deficiency is rare-the patient will have a history of bleeding-
cue bleeding history...
Congenital factor VII deficiency is rare-the patient will have a history of bleeding-
cue bleeding history...
5/ Congenital Factor VII deficiency can be effectively ruled out by a normal bleeding history and any previously normal PT results
For acquired PT(by far and away more common than inherited) we often suggest a trial of vitamin K (10mg PO/IV for 3 days) and repeat
For acquired PT
(by far and away more common than inherited) we often suggest a trial of vitamin K (10mg PO/IV for 3 days) and repeat
6/ If the patient is on warfarin, use the INR (an internationally standardised modification of the PT) rather than PT to guide reversal according to local guidance-the #bukumedicine app includes the Northern region haematology consultants group guidance for reference
7/ FFP CANNOT reduce/improve a PT of 19/20 seconds or less and therefore giving it in this context before a procedure, especially in someone who is not bleeding;
- Will not reduce bleeding
- Will expose patient to blood product
- Will put them at risk of TACO
...
- Will not reduce bleeding
- Will expose patient to blood product
- Will put them at risk of TACO
...
8/ In this scenario (procedure planned and PT outside normal range but under 19/20) discuss with haematology for advice about other means of reducing the bleeding risk e.g tranexamic acid/alternative procedures such as transjugular liver biopsy rather than percutaneous
9/ If the PT is over 20, and surgery is planned or there is bleeding, FFP may be beneficial but you need good doses (and thus a reasonable volume of FFP) for a meaningful improvement in the PT
The dose is 12-15ml/kg i.e a 70kg adult needs around 900ml-1L
The dose is 12-15ml/kg i.e a 70kg adult needs around 900ml-1L
10/ As a rule of thumb, coagulation tests are difficult to correlate to clinical phenotypes and rarely helpful if done without a specific reason
Try to resist performing on patients unless you feel it would change patient management
Try to resist performing on patients unless you feel it would change patient management
11/ In summary;
Prolonged PT-common +++ in inpatients and almost always due to consumption in acute illness/liver impairment (acute or chronic). Vitamin K very useful, FFP in certain circumstances. Inherited bleeding disorder incredibly rare
#MedEd #MedTwitter #tipsfornewdocs
Prolonged PT-common +++ in inpatients and almost always due to consumption in acute illness/liver impairment (acute or chronic). Vitamin K very useful, FFP in certain circumstances. Inherited bleeding disorder incredibly rare
#MedEd #MedTwitter #tipsfornewdocs
