Dabigatran plasma levels, aPTT and thromboelastography in patients with AF: implications for allowing early...

According to current recommendations, patients on dabigatran should stop the drug 24-96 h before scheduled surgery. This may seem too long for non-elective cases. The aim of our study was to assess the number of patients on dabigatran who could theoretically undergo surgery 12 h post last drug dosing. We measured dabigatran plasma trough concentration by Hemoclot assay in 75 consecutive patients receiving dabigatran. Coagulation was assessed by aPTT and thromboelastography (TEG). Plasma levels ≤30 ng/ml were considered low. TEG parameters measured were clot reaction time (R), clot growth index (k), angle (α), maximal amplitude (MA) and the percentage of clot lysed after 30 min (LY30). Twelve patients (16%) had low plasma dabigatran levels 11.6 ± 0.9 h post last dosing. These patients compared to those with higher levels had significantly different aPTT (37.7 ± 4.4 vs. 49.6 ± 9.2 s; p < 0.001) and TEG R (6.7 ± 1.3 vs. 8.4 ± 2.6 min; p = 0.002). Only three of the patients with low levels had an aPTT >40 s. Within those with levels >30 ng/ml, four patients (6.4%) had plasma dabigatran levels ≥200 ng/ml, all with aPTT >65 s and TEG R >11 min. When the analysis was restricted to patients with creatinine clearance >80 ml/min, six (27.3%) had low plasma dabigatran levels. In this theoretical study, with a low risk population, it is suggested that one-sixth of patients receiving dabigatran have low drug concentrations at 12 h. Further studies are needed to confirm that such patients with low trough levels can actually undergo safely early surgery if necessary.