Summary

Bridging anticoagulation with low-molecular-weight heparin(LMWH) is common in patients who require temporary interruptionof warfarin before surgery or a procedure, but whethersuch patients have a residual anticoagulant effect just before aprocedure is not known. Consecutive patients who receivedbridging anticoagulation with LMWH had anti-Xa levelsmeasured just before a procedure.The proportion of patientswith a residual anticoagulant effect, defined as an anti-Xa level= 0.10 IU/ml, was determined. Multivariable regression analysisidentified predictors of a residual anticoagulant effect, expressedas an odds ratio (OR) and corresponding 95% confidence interval (CI). A pre-procedure residual anticoagulant effect wasdetected in 12 of 73 (16%) patients overall, in 11 of 37 (30%) patientswho received therapeutic-dose LMWH, and in 1 of 36 patients(3%) who received low-dose LMWH. Receiving therapeutic-dose LMWH (OR = 118.8; 95% CI: 5.8, 999.9), and increasingage (OR = 4.0; 95% CI: 1.3, 12.5) were predictors of aresidual pre-procedure anticoagulant effect. In patients whorequire bridging anticoagulation with LMWH, a residual anticoagulanteffect from LMWH is detected in 1 of 6 patients, andreceiving therapeutic-dose LMWH is the strongest predictor ofsuch an effect.