The authors of a related commentary note that recent literature has highlighted the bleeding risk conferred by use of full-dose anticoagulants following surgical procedures, particularly when started in the first 2 to 3 days. However patients with prior VTE are at a particularly high risk of recurrence during the post-operative period, as surgery itself is a known precipitant of VTE.
This study included 1178 patients who were receiving warfarin for the secondary prevention of VTE. The procedures for which treatment was interrupted were mainly GI tract endoscopies (37%), followed by orthopaedic, spinal or intracranial and non-major abdominal or thoracic procedures. Patients were stratified according to their underlying risk of recurrent VTE according to guidelines from the ACCP – 79% were low-risk, 17.9% intermediate and 3.1% high-risk. Bridging was not standardised and was received by 28.7%, 33.6% and 63.2%, respectively. The bridging doses used were therapeutic in the majority of cases (72.5%).
The primary outcome of the study was clinically relevant bleeding occurring up to 30 days following the procedure. There were 15 events in the bridging group (2.7%) and 2 events in the no-bridging group (0.2%) – these were mainly related to the administration of the bridging agent or a complication of the procedure. Recurrent VTE events were evaluated as a secondary endpoint – there were no events in the bridging group and 3 (0.2%) in the no-bridging group (none of these were in high-risk patients). The researchers conclude that the risk of bleeding associated with bridge therapy appeared to outweigh the potential benefits in their study population.
The study has several limitations, due to its retrospective design. For example there was no adjustment for potential confounding (due to low overall event rates) and a reliance on administratively collected data (possible omission or misclassification of procedures and outcomes). Furthermore there was a lack of information on anticoagulant timing, and only a small number of patients at VTE high-risk who received no bridging were included (patients were mainly low-risk and had already received >12 months of anticoagulation prior to the procedure).
The commentary supports the authors’ conclusion that the vast majority of patients receiving anticoagulants for a history of VTE should not be given therapeutic-dose bridge therapy. Although there are undoubtedly some high-risk patients who will require bridging therapy (e.g. acute VTE in the preceding month), they suggest that in most cases it is probably safer to simply allow the oral anticoagulant to wash out before the procedure and, if indicated based on the type of surgery, to use routine prophylactic-dose anticoagulation therapy afterward. They call into question the ACCP risk-stratification system and say that further research is needed to identify patient- or procedure-related characteristics that predict a high risk of VTE recurrence during interruption of warfarin therapy.
The British Committee for Standards in Haematology (BCSH) last issued guidelines on oral anticoagulation with warfarin in 2011 (fourth edition – please see the link below for details). The section on perioperative anticoagulation recommends that patients with a VTE within the previous 3 months should be considered for bridging therapy; those with VTE more than 3 months earlier can be given prophylactic dose LMWH (or a suitable alternative) rather than bridging therapy. It acknowledges the high-risk of bleeding associated with post-operative bridging, and therefore its use requires careful consideration.