In vitro effects of emicizumab on activated clotting time in blood samples from cardiac surgical patients

Authors

Kenichi A. Tanaka, Department of Anesthesiology, University of Oklahoma College of Medicine, Oklahoma City, Oklahoma, USA.
Reney Henderson, Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Kiruphagaran Thangaraju, Departments of Pathology and Pediatrics, Center for Blood Oxygen Transport, University of Maryland, Baltimore, Maryland, USA.
Yoshihisa Morita, Department of Anesthesiology, University of Oklahoma College of Medicine, Oklahoma City, Oklahoma, USA.
Michael A. Mazzeffi, Department of Anesthesiology & Critical Care Medicine, George Washington University School of Medicine, Washington, District of Columbia, USA.
Erik Strauss, Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Upendra Katneni, Departments of Pathology and Pediatrics, Center for Blood Oxygen Transport, University of Maryland, Baltimore, Maryland, USA.
Paul W. Buehler, Departments of Pathology and Pediatrics, Center for Blood Oxygen Transport, University of Maryland, Baltimore, Maryland, USA.

Document Type

Journal Article

Publication Date

1-1-2022

Journal

Haemophilia : the official journal of the World Federation of Hemophilia

Volume

28

Issue

1

DOI

10.1111/hae.14452

Keywords

Haemophilia A with inhibitors; activated clotting time; cardiopulmonary bypass; emicizumab

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.

APA Citation

Tanaka, Kenichi A.; Henderson, Reney; Thangaraju, Kiruphagaran; Morita, Yoshihisa; Mazzeffi, Michael A.; Strauss, Erik; Katneni, Upendra; and Buehler, Paul W., "In vitro effects of emicizumab on activated clotting time in blood samples from cardiac surgical patients" (2022). GW Authored Works. Paper 449.
https://hsrc.himmelfarb.gwu.edu/gwhpubs/449

Department

Anesthesiology and Critical Care Medicine