Is there any case we can use warfarin for DVT without the use of heparin (as in subacute or chronic cases) and if the patient is already started on warfarin and has taken it for several days, will there be a use to recommend adding LMWH?
It is much better to overlap LMWH with warfarin at least for first two days of warfarin therapy. Remember that Protein C will be lowered with warfarin therapy before Factor II, X and IX! So introducing warfarin only will make thrombosis worse. If patient takes warfarin already for several days, it is not necessary to add LMWH if the simptoms of thrombosis are not present. Sometimes we add LMWH therapy to warfarin therapy, if the patient has simptoms of thrombosis getting worse, even if the Prothrombin time is in the therapeutic range.
Warfarin should be used in conjunction with Heparin for at least 24 hours, (24-48 hours debatable, in our hospital we administrate it for the first 24 hours), there is a risk for skin necrosis or tissue necrosis(( which are believed to be due to small microthrombosis), as our colleague mentioned, protein C has a shorter half life than factor II and X, the existing protein C depletes before existing factor II and X deplete, and before warfarin can reduce factor II and X production, resulting a hypercogulated state .
overall I would say its a chance for patient to develop tissue necrosis its better not risk it.
The antithrombotic activity of warfarin occur after 5-7 days from the beginning of treatment (anticoagulant activity may be present much earlier). Thus, you have to overlap heparin waiting for the full antithrombotic action of warfarin.
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