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- Title
In vitro effects of emicizumab on activated clotting time in blood samples from cardiac surgical patients.
- Authors
Tanaka, Kenichi A.; Henderson, Reney; Thangaraju, Kiruphagaran; Morita, Yoshihisa; Mazzeffi, Michael A.; Strauss, Erik; Katneni, Upendra; Buehler, Paul W.
- Abstract
Background: Heparin management in hemophilia A (HA) patients with a factor VIII (FVIII) inhibitor can be challenging due to severe activated clotting time (ACT) prolongations. It is important to better understand the impact of emicizumab, a FVIII mimetic on ACT, and tissue factor (TF)‐based coagulation assays. Methods: Whole blood from 18 patients undergoing cardiopulmonary bypass (CPB) were mixed in vitro with pooled normal plasma, FVIII‐deficient or FVIII‐inhibitor plasma to affect functional FVIII levels. ACTs and heparin concentration by protamine titration were measured in whole blood mixture with/without emicizumab (50‐100 μg/ml). Thrombin generation and plasmin generation were measured in the patient's plasma mixed with normal plasma or FVIII‐inhibitor plasma to assess the impact of emicizumab under low TF activation. Results: FVIII inhibitors prolonged ACTs by 2.2‐fold compared to those in normal plasma mixture at baseline. During CPB, ACTs in normal plasma mixture, and FVIII‐deficient mixture were in 400s, but ACTs reached 900s in FVIII‐inhibitor mixture. Emicizumab shortened ACTs by up to 100s in normal plasma mixture, and FVIII‐deficient mixtures. ACTs remained over 600s in FVIII‐inhibitor mixture, despite adding emicizumab at 100 μg/ml. Heparin concentration measured by TF‐based protamine titration was unaffected. Emicizumab enhanced thrombin peak in the presence of FVIII inhibitors, whereas plasmin generation was mainly affected by thrombin generation, and systemic use of ɛ‐aminocaproic acid. Conclusions: FVIII inhibitors extensively prolong ACTs in heparinized whole blood, and clinical levels of emicizumab partially reverse ACT values. Protamine titration should be considered for optimal heparin monitoring in emicizumab‐treated patients with FVIII inhibitors.
- Subjects
EMICIZUMAB; BLOOD coagulation factor VIII antibodies; BLOOD coagulation; CARDIAC patients; BLOOD coagulation factor VIII; CARDIOPULMONARY bypass; BLOOD sampling
- Publication
Haemophilia, 2022, Vol 28, Issue 1, p183
- ISSN
1351-8216
- Publication type
Article
- DOI
10.1111/hae.14452