Summary
Treatment with vitamin K antagonists (VKAs) has to be interrupted when invasive procedures
are planned. We compared various methods of interruption in patients on acenocoumarol
or phenprocoumon in a prospective study. In patients on acenocoumarol (n=141), 99
stopped three days before the intervention and 42 stopped two days before. All patients
on phenprocoumon (n=111) received vitamin K two days before the intervention, and
55 of these patients discontinued phenprocoumon, whereas 56 did not stop. In a subset
of 30 patients we determined International Normalized Ratios (INRs) and coagulation
factors II,VII, X and protein C. The mean INR after stopping acenocoumarol for three
days was significantly lower than after two days (1.1 vs. 1.3, p=<0.0001), but its
clinical relevance may be trivial. In patients using phenprocoumon, the mean INR on
the day of the intervention was only slightly lower after stopping the VKAs (1.5 vs.
1.6, p=0.0407), but a similar proportion of patients had an INR ≤1.4. On the day of
the intervention, in the acenocoumarol group mean plasma levels of all coagulation
factors were higher than 50% and in the phenprocoumon group higher than 25%. We conclude
that acenocoumarol can be stopped two days before an invasive procedure that is associated
with a low or moderate bleeding risk and three days before an intervention with a
higher bleeding risk. For phenprocoumon, administration of vitamin K two days before
an intervention results in an acceptable INR during the intervention, regardless whether
phenprocoumon is interrupted or not.
Keywords
Acenocoumarol - phenprocoumon - invasive procedures - coagulation factors
