A Multicenter, Randomized, Double-Blind, Placebo-Controlled Trial of Preoperative Antithrombin Supplementation in Patients at Risk for Antithrombin Deficiency After Cardiac Surgery.

BACKGROUND: Antithrombin (AT) activity is reduced during cardiac operations with cardiopulmonary bypass (CPB), which is associated with adverse outcomes. Preoperative AT supplementation, to achieve >58% and <100% AT activity, may potentially reduce postoperative morbidity and mortality in cardiac operations with CPB. This prospective, multicenter, randomized, double-blind, placebo-controlled study was designed to evaluate the safety and efficacy of preoperative treatment with AT supplementation in patients at risk for low AT activity after undergoing cardiac surgery with CPB. METHODS: A total of 425 adult patients were randomized (1:1) to receive either a single dose of AT (n = 213) to achieve an absolute increase of 20% above pretreatment AT activity or placebo (n = 212) before surgery. The study duration was approximately 7 weeks. The primary efficacy end point was the percentage of patients with any component of a major morbidity composite (postoperative mortality, stroke, acute kidney injury [AKI], surgical reexploration, arterial or venous thromboembolic events, prolonged mechanical ventilation, and infection) in the 2 groups. Secondary end points included AT activity, blood loss, transfusion requirements, duration of intensive care unit (ICU), and hospital stays. Safety was also assessed. RESULTS: Overall, 399 patients (men, n = 300, 75.2%) with a mean (standard deviation [SD]) age of 66.1 (11.7) years, with the majority undergoing complex surgical procedures (n = 266, 67.9%), were analyzed. No differences in the percentage of patients experiencing morbidity composite outcomes between groups were observed (AT-treated 68/198 [34.3%] versus placebo 58/194 [29.9%]; P = .332; relative risk, 1.15). After AT infusion, AT activity was significantly higher in the AT group (108% [42-143]) versus placebo group (76% [40-110]), and lasted up to postoperative day 2. At ICU, the frequency of patients with AT activity ≥58% in the AT group (81.5%) was significantly higher ( P < .001) versus placebo group (43.2%). Secondary end point analysis did not show any advantage of AT over placebo group. There were significantly more patients with AKI ( P < .001) in the AT group (23/198; 11.6%) than in the placebo group (5/194, 2.6%). Safety results showed no differences in treatment-emergent adverse events nor bleeding events between groups. CONCLUSIONS: AT supplementation did not attenuate adverse postoperative outcomes in our cohort of patients undergoing cardiac surgery with CPB.

ISTH guidelines for antithrombotic treatment in COVID-19.

Antithrombotic agents reduce risk of thromboembolism in severely ill patients. Patients with coronavirus disease 2019 (COVID-19) may realize additional benefits from heparins. Optimal dosing and timing of these treatments and benefits of other antithrombotic agents remain unclear. In October 2021, ISTH assembled an international panel of content experts, patient representatives, and a methodologist to develop recommendations on anticoagulants and antiplatelet agents for patients with COVID-19 in different clinical settings. We used the American College of Cardiology Foundation/American Heart Association methodology to assess level of evidence (LOE) and class of recommendation (COR). Only recommendations with LOE A or B were included. Panelists agreed on 12 recommendations: three for non-hospitalized, five for non-critically ill hospitalized, three for critically ill hospitalized, and one for post-discharge patients. Two recommendations were based on high-quality evidence, the remainder on moderate-quality evidence. Among non-critically ill patients hospitalized for COVID-19, the panel gave a strong recommendation (a) for use of prophylactic dose of low molecular weight heparin or unfractionated heparin (LMWH/UFH) (COR 1); (b) for select patients in this group, use of therapeutic dose LMWH/UFH in preference to prophylactic dose (COR 1); but (c) against the addition of an antiplatelet agent (COR 3). Weak recommendations favored (a) sulodexide in non-hospitalized patients, (b) adding an antiplatelet agent to prophylactic LMWH/UFH in select critically ill, and (c) prophylactic rivaroxaban for select patients after discharge (all COR 2b). Recommendations in this guideline are based on high-/moderate-quality evidence available through March 2022. Focused updates will incorporate future evidence supporting changes to these recommendations.

Patient blood management: recommendations rrom the 2018 Frankfurt consensus conference

What is the current evidence base for patient blood management (PBM) in adults, and what international clinical recommendations can be derived for preoperative anemia, red blood cell transfusion thresholds, and PBM implementation strategies? Diagnosis and management of preoperative anemia is crucial, and iron-deficient anemia should be treated with iron supplementation. Red blood cell transfusion thresholds for critically ill, clinically stable patients (hemoglobin concentration <7 g/dL), patients undergoing cardiac surgery (hemoglobin concentration <7.5 g/dL), patients with hip fractures and cardiovascular disease or risk factors (hemoglobin concentration <8 g/dL), and hemodynamically stable patients with acute gastrointestinal bleeding (hemoglobin concentration 7-8 g/dL) are relatively well defined, although the quality of evidence is moderate to low. Further high-quality research to support PBM is required for a range of clinical scenarios and implementation of PBM programs.

Discontinuation and Management of Direct-Acting Anticoagulants for Emergency Procedures.

Patients taking direct oral anticoagulants (DOACs) who then need an emergency invasive procedure require specialized management strategies. Appropriate patient evaluation includes assessment of the current anticoagulation state, including timing of the last dose. DOACs require particular coagulation assays to measure anticoagulation levels accurately, although standard coagulation screening tests may provide qualitative guidance. Specialty societies have endorsed general recommendations for patient management to promote hemostasis in anticoagulated patients requiring surgery or other invasive procedures. These include general stopping rules (such as ≥24 hours for low-risk procedures and ≥48 hours for high-risk surgery with normal renal function) for elective procedures. Bridging therapy when oral anticoagulant treatment is interrupted has recently been questioned, depending on the clinical scenario. Novel agents for the reversal of DOAC-induced anticoagulation have recently been developed. Idarucizumab, a humanized monoclonal antibody fragment that selectively binds dabigatran, was recently approved for clinical use in patients with life-threatening or uncontrolled bleeding, and for patients requiring emergency interventions. Idarucizumab can streamline the pre- and periprocedural anticoagulation management of dabigatran-treated patients, as it provides fast, complete, and sustainable reversibility. Andexanet alfa is an inactive, decoy factor Xa (FXa) molecule that binds FXa inhibitors, and ciraparantag is a synthetic molecule designed to bind fractionated and unfractionated heparins, and each of the currently approved DOACs. As clinical development of the additional anti-FXa-specific anticoagulant reversal agents proceeds, the respective role of each in the management of emergency bleeding events and invasive procedures will be better defined, and it is hoped they will make important contributions to patient care.

Andexanet alfa for the reversal of Factor Xa inhibitor related anticoagulation.

Andexanet alfa is a specific reversal agent for Factor Xa inhibitors. The molecule is a recombinant protein analog of factor Xa that binds to Factor Xa inhibitors and antithrombin:LMWH complex but does not trigger prothrombotic activity. In ex vivo, animal, and volunteer human studies, andexanet alfa (AnXa) was able to dose-dependently reverse Factor Xa inhibition and restore thrombin generation for the duration of drug administration. Further trials are underway to examine its safety and efficacy in the population of patients experiencing FXa inhibitor-related bleeding.

Anti-factor IXa Aptamer reduces propagation of thrombin generation in plasma anticoagulated with warfarin.

BACKGROUND: Warfarin is routinely used in the prevention and treatment of prothrombotic events. During initiation of warfarin therapy levels of factor (F) VII and protein C decrease rapidly but prothrombin, FIX and FX decline much slower. Therefore, propagation of thrombin generation (TG) remains unaffected much longer, increasing the risk of inadequate anticoagulation. Recently, a novel agent, anti-IXa aptamer, RB006, has been developed. Therefore, we have evaluated the in vitro effects of this agent in warfarin plasma. METHODS: The investigation consisted of two parts. First, a computer simulated time course of TG with warfarin alone and in combination with FIXa inhibition was evaluated and, second, normal volunteer, protein C deficient, FVII deficient and commercial warfarin plasmas (INR 2.1 and 3.1) were spiked with increasing concentrations of aptamer (0-24 microg/ml) and its anticoagulant effects were evaluated using prothrombin time (PT), activated partial thromboplastin time (aPTT) and TG with tissue factor and Actin as activators. Direct effects of aptamer on protein C were also evaluated. RESULTS: Simulation of coagulation during warfarin induction showed that TG can be significantly delayed and decreased by inhibiting FIXa (i.e., with anti-FIXa aptamer). The anti-FIXa aptamer inhibited TG in all tested plasmas, but was most efficacious in warfarin and FVII deficient plasma. The aptamer itself did not inhibit protein C and had no effect on PT, but concentration-dependently increased aPTT. CONCLUSION: The anti-FIXa aptamer potentiates the inhibitory effects of warfarin on TG, and may fill the need as an adjuvant agent during initiation of warfarin therapy.

Evaluation of a novel kallikrein inhibitor on hemostatic activation in vitro.

BACKGROUND: DX-88 is a potent kallikrein inhibitor that is being studied for the treatment of hereditary angioedema (HAE) and represents a potential alternative to aprotinin in cardiac surgical patients. The current study was designed to evaluate in vitro effects of DX-88 on coagulation in comparison with aprotinin. METHODS: Blood samples were obtained from consented 12 healthy volunteers. DX-88 or aprotinin was added to blood at 200 and 800 kallikrein inhibitory units (KIU) per milliliter for aprotinin, and at 1.1, 2.2, or 8.8 microg/ml for DX-88. Thromboelastography (TEG) was performed using celite, kaolin, or tissue factor (TF) activation. Kaolin-based activated clotting times (ACTs) were measured at different heparin levels. The whole blood prothrombin time (PT)/PTT values were also measured. The endogenous thrombin generation was assessed with a fluorogenic assay using platelet-poor plasma (PPP). RESULTS: With celite and kaolin activation of TEG, the reaction time was prolonged with DX-88 and aprotinin. With tissue factor activation, TEG parameters were not affected. DX-88 caused dose-dependent kaolin-ACT prolongation that was augmented by increasing doses of heparin. DX-88 or aprotinin had no significant effects on the PT values, but PTT values were dose-dependently prolonged. Both agents delayed the onset of thrombin generation when PTT reagent was used as a trigger, whereas no change was observed when tissue factor was used. CONCLUSION: We found that DX-88 delayed contact activator induced coagulation without affecting tissue factor mediated coagulation. For evaluation of coagulation during DX-88 therapy, the use of PT or tissue factor-activated TEG may be preferable.