1/7. Prothrombin time (PT) measures the extrinsic coagulation cascade. The only 'major' clotting factor in the extrinsic pathway is factor VII. This is the clotting factor with the shortest half life, and explains why the PT is so often prolonged in unwell patients
2/7. It also makes a long PT relatively easy to investigate and manage. The absolute majority of patients with a long PT will either be vitamin K deficient, have factor VII deficiency due to consumption in sepsis/bleeding or liver disease.
3/7. Warfarin and the DOACS (to a varying degree) will represent most of the rest of prolonged PT results. Factor VII deficiency is incredibly rare, and will have been present from birth, therefore if the patient has had a normal PT in the past...
4/7... and no significant bleeding history, then factor VII deficiency is effectively ruled out. To manage a long PT, check the patient bleeding history and look for old results. If there is a convincing bleeding history and no 'normal' PT in the past, discuss with haematology
5/7. However for almost all patients a trial of 10mg vitamin K for 3 days will correct the long PT. FFP can only bring a PT down to 19/20 seconds at best and therefore there is no point giving FFP at these PT levels unless there is ongoing blood loss.
6/7. If pre-procedure, for example, giving FFP to correct a clotting time of 19/20 seconds will produce little or no change, and at the same time expose the patient to a blood product and 750ml-1L of fluid, risking fluid overload
7/7. In summary, almost all long PT results will be due to reversible causes (with vitamin K) or anticoagulants. A trial of vitamin K would be the usual first line treatment. Only try to 'correct' a PT of 19/20 in rare circumstances (only bleeding the main one). #blooducation
