Use of specific anti-Xa levels in acute kidney injury to transition patients from oral factor Xa inhibitors to i.v. heparin infusion.

This case series presents 3 patients with acute kidney injury taking apixaban or rivaroxaban and transitioning to a heparin infusion. Case 1 was a 78-year-old man admitted with respiratory failure, acute decompensated heart failure, and acute kidney injury. He was taking apixaban for atrial flutter. He was transitioned to an i.v. heparin infusion and had 2 consecutive heparin antifactor-Xa levels greater than 2 units/mL. Heparin was held and resumed about 36 hours later when the apixaban anti-Xa level was less than 50 ng/mL. Case 2 was a 55-year-old man admitted with acute kidney injury, taking apixaban for a recent deep vein thrombosis. Apixaban anti-Xa levels were monitored and i.v. heparin was initiated when the level was less than 100 ng/mL, about 56 hours after the last apixaban dose. Case 3 was a 64-year-old woman admitted with sepsis and acute kidney injury taking rivaroxaban for pulmonary embolism, which occurred 2 weeks prior to admission. Rivaroxaban anti-Xa levels were monitored and i.v. heparin was initiated about 36 hours after the last dose when the level was less than 100 ng/mL. The management strategy did not lead to any thrombotic outcomes; however, 1 patient experienced bleeding. Specific anti-Xa levels for rivaroxaban and apixaban appeared to be helpful in the transition of 3 patients to unfractionated heparin infusions in the setting of acute kidney injury. These levels provided enhanced, individualized care and likely helped avoid over and under anticoagulation.

Zochert S ，Oltman KM ，Elgersma BM ，Hellwig TR ，Gulseth MP ... -  《-》

Influence of apixaban on antifactor Xa levels in a patient with acute kidney injury.

The case of a patient requiring conversion from apixaban to heparin in the setting of acute kidney injury is reported. A 70-year-old man was initiated on apixaban 5 mg twice daily for new-onset, nonvalvular atrial fibrillation with a CHA2DS2-VASc score of 4, indicating a high risk of stroke. Soon after starting apixaban, he experienced pulmonary edema with pneumonia requiring hospitalization. During the course of hospitalization, the patient developed acute kidney injury requiring hemodialysis, and apixaban was stopped due to concerns about altered pharmacokinetics and impaired drug elimination in this setting. A heparin infusion was started 36 hours after the last dose of apixaban was administered. Antifactor Xa levels were monitored consistent with the hospital's standard practice protocols. The initial and repeat antifactor Xa concentrations were elevated (1.8-4.4 IU/mL) for up 72 hours after stopping the heparin infusion. Given the suspected interference of apixaban with standard antifactor Xa level monitoring, the heparin protocol was modified to reflect drip-rate adjustments based on activated partial thromboplastin times (aPTTs). The hospital protocol for heparin infusions was reinstituted on hospital day 7, with dosage adjustments based on antifactor Xa levels. The patient remained on a continuous heparin infusion for atrial fibrillation for the remainder of his hospitalization without complications or bleeding events. A 70-year-old man with new-onset nonvalvular atrial fibrillation and receiving apixaban discontinued this therapy and was given heparin instead due to acute kidney injury. His heparin dosage was successfully adjusted based on antifactor Xa levels and aPPTs.

Wendte J ，Voss G ，VanOverschelde B 《-》

Transitioning hospitalized patients from rivaroxaban or apixaban to a continuous unfractionated heparin infusion: A retrospective review.

To determine a patient's clinical course based on the use of an activated partial thromboplastin time (aPTT) or heparin anti-Xa assay when transitioning from rivaroxaban or apixaban to an unfractionated heparin infusion. A retrospective chart review was conducted to investigate how unfractionated heparin infusions were managed at a tertiary care hospital in the setting of recent apixaban or rivaroxaban administration. Patients were separated into 2 cohorts based on the chosen heparin infusion monitoring assay: heparin anti-Xa or aPTT. The primary composite outcome was total number of bleeding and thrombotic events; the secondary composite outcome was average incidence of heparin infusion holds and rate changes per patient. Data were collected from 76 patients (heparin anti-Xa = 69, aPTT = 7). Due to the limited number of patients within the aPTT cohort, this data was excluded from the analysis, and heparin anti-Xa descriptive statistics were reported without statistical comparisons. In the heparin anti-Xa group, a total of 10 bleeds and 1 thrombus were discovered. Additionally, the average number of infusion holds and rate changes was 0.841 and 2.65 times per patient, respectively, for those patients monitored via heparin anti-Xa assay. In the presence of a recently administered oral anti-Xa anticoagulant, more down-titrations occurred in the initial 6 hours of the heparin infusion when measuring anti-Xa activity, and most up-titrations occurred after 36 hours. Baseline heparin anti-Xa activity may be a useful tool to identify patients with residual plasma concentrations of apixaban and rivaroxaban to help better individualize heparin therapy.

Smith AR ，Dager WE ，Gulseth MP 《-》

DOAC plasma levels measured by chromogenic anti-Xa assays and HPLC-UV in apixaban- and rivaroxaban-treated patients from the START-Register.

To measure direct factor Xa inhibitor (apixaban, edoxaban, rivaroxaban) concentrations, dedicated chromogenic anti-Xa assays are recommended as suitable methods to provide rapid drug quantification. Moreover, the high-performance liquid chromatography with ultraviolet detection (HPLC-UV) is reported as a reliable quantitative technique. We investigated seven anti-Xa assays and an HPLC-UV method for measurement of apixaban and rivaroxaban levels in patients enrolled in the START-Register. A total of 127 apixaban and 124 rivaroxaban samples were tested by HPLC-UV and the following anti-Xa assays: Biophen DiXaI and Heparin LRT (Hyphen BioMed), Berichrom and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen). Each method was performed in one of the participating laboratories: Bologna, Cremona, Florence, and Padua. Our data confirmed the overestimation of apixaban and rivaroxaban levels by the antithrombin-supplemented anti-Xa method (Berichrom). Performances and reproducibility of the six anti-Xa assays not supplemented with antithrombin and the HPLC-UV method were good, with limits of quantification from 8-39 ng/mL (apixaban) and 15-33 ng/mL (rivaroxaban). The six chromogenic methods showed good concordances with the quantitative HPLC-UV [bias: -26.9-22.3 ng/mL (apixaban), -11.3-18.7 ng/mL (rivaroxaban)]. Higher bias and wider range between limits of agreement were observed at higher concentrations [<100 ng/mL: bias -21.3-4.1 ng/mL (apixaban) and -6.2-3.8 ng/mL (rivaroxaban); >200 ng/mL: bias -42.2-36.8 ng/mL (apixaban) and -20.1-68.9 ng/mL (rivaroxaban)]. Overall, the anti-Xa assays not supplemented with antithrombin and the HPLC-UV method proved to be suitable for apixaban and rivaroxaban quantification.

Cini M ，Legnani C ，Padrini R ，Cosmi B ，Dellanoce C ，De Rosa G ，Marcucci R ，Pengo V ，Poli D ，Testa S ，Palareti G ... -  《-》

Using a low-molecular weight heparin-calibrated anti-factor Xa assay to assess the concentration of apixaban and rivaroxaban.

Direct oral anticoagulant (DOAC)-inhibiting factor Xa (FXa-DOAC) are being increasingly used as prophylaxis of venous thromboembolism and for prevention of stroke in patients with atrial fibrillation. In contrast to vitamin K antagonists, DOACs do not require monitoring in general. However, it is sometimes of value in the acute setting, for instance when considering a reversal agent in uncontrolled bleeding in patients on DOAC. We evaluated if a low-molecular weight heparin (LMWH)-calibrated anti-factor Xa assay could be used to estimate FXa-DOAC concentration in the concentration range <100 ng/mL by spiking known concentrations of FXa-DOAC and from those result calculate the FXa-DOAC concentration from the response of the LMWH assay. This procedure was then evaluated by comparing the result with a drug-calibrated chromogenic assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) on clinical plasma samples from patients treated with apixaban or rivaroxaban. Although the measuring range was narrower for the LMWH-calibrated assay, concentrations recalculated from the LMWH assay was comparable with those measured by the drug-calibrated method when compared with LC-MS/MS. We suggest that an LMWH-calibrated anti-factor Xa assay can be used after characterization of the response of FXa-DOACs to give guidance on the concentration of apixaban and rivaroxaban. Shorter turnaround time than LC-MS/MS and the greater availability than drug-calibrated chromogenic assays could make this a valuable option in the acute setting.

von Horn H ，Rasmusson A ，Söderblom L ，Malmström RE ，Antovic J ... -  《-》