Factor IX from prothrombin complex concentrate augments low dose tissue factor-triggered thrombin generation in vitro

Background: Prothrombin complex concentrate (PCC) is increasingly used to correct acquired coagulopathy in trauma and surgery. Dosing of PCC is guided by the prothrombin time, which only reflects the onset of thrombin generation, but does not account for variations in intrinsic pathway coagulation factors, including factor IX (FIX). We hypothesised that FIX contained in PCC could strongly influence thrombin generation patterns. Methods: Pooled normal, FIX-deficient, and warfarinised plasma were used to analyse the effects of FIX contained in PCC. PCC was evaluated at final concentrations of 0.2 and 0.4 IU ml−1 in FIX-deficient and normal plasma, and at 0.6 IU ml−1 in warfarinised plasma with elevated FVIII (1.5 IU ml−1), 40% dilution with saline, or both. The effects on thrombin generation were assessed by measuring both procoagulant and inhibitory segments. Results: FIX-deficient plasma had lower peak thrombin generation [30.6 (20.5–35.8) nM vs 130.2 (107–168) nM] and endogenous thrombin potential [472 (391–532) nM vs 1096 (958–1190) nM] than normal plasma. PCC addition resulted in significant increases of peak thrombin generation [81.8 (37.3–98.3) nM] and endogenous thrombin potential [808 (472–842) nM] in FIX-deficient plasma. The combination of FVIII and PCC resulted in greater increases relative to each agent alone, restoring normal thrombin generation. After 40% dilution, adding PCC, FVIII, or both, to FIX-deficient plasma increased peak thrombin generation, and prolonged the inhibitory phase of the endogenous thrombin potential. Conclusions: FIX derived from PCC strongly enhances tissue factor-triggered thrombin generation in the presence of elevated FVIII activity. Haemodilution further enhances procoagulant effects of FIX and FVIII by slowing down inhibition of procoagulant enzymes. Dosing of PCC per prothrombin time may underestimate PCC\u27s procoagulant potential because it does not account for intrinsic tenase or antithrombin activity

Elevated fibrinogen, von Willebrand factor, and Factor VIII confer resistance to dilutional coagulopathy and activated protein C in normal pregnant women

© 2019 British Journal of Anaesthesia Background: Gestational changes in coagulation factor concentrations include elevations in fibrinogen, Factor VIII, and von Willebrand factor (vWF). We hypothesised that blood samples from term pregnant (TP) subjects are less prone to coagulation disturbances from haemodilution compared with those from non-pregnant (NP) females. Methods: Blood samples were collected from 15 NP and 15 TP subjects. In vitro haemodilution with normal saline was assessed by modified Clauss fibrinogen assay, factor activity, flow-chamber assay, and thromboelastometry. The impact of human fibrinogen concentrate (hFC), cryoprecipitate, and vWF/Factor VIII (FVIII) concentrate replacement in diluted TP and NP blood was compared. Thrombin generation and activated protein C sensitivity were assessed. Results: TP blood contained twice the concentrations of fibrinogen, FVIII, and vWF relative to NP blood (P\u3c0.0001). Platelet thrombus formation (PTF) under flow was reduced by 99.2% and 69.2% in diluted NP and TP blood, respectively. Platelet thrombus formation was partially restored by adding vWF/FVIII, but not hFC or cryoprecipitate. Fibrin clot firmness approached the threshold of 10 mm in diluted NP blood, and clot firmness was effectively restored by hFC, but not by vWF/FVIII. In the presence of thrombomodulin, peak thrombin generation was decreased by 86.7% in NP plasma, but by 31.8% in TP plasma (P\u3c0.0001 vs NP plasma), indicating reduced activated protein C sensitivity in TP plasma. Both elevated FVIII and haemodilution contributed to activated protein C insensitivity. Conclusions: Our in vitro model showed relative resistance of TP blood to dilutional coagulation changes with respect to platelet adhesion, fibrin polymerisation, and thrombin generation. Careful therapeutic monitoring for different pro-haemostatic agents in pregnant women is warranted

Therapeutic plasma exchange in heart transplantation: role of coagulation assessment with thromboelastometry

Abstract Therapeutic plasma exchange (TPE) is a potentially life-saving procedure which effectively removes donor-specific human leukocyte antigen (HLA) antibodies from the bloodstream, allowing critically ill heart transplant recipients to receive a donor organ with less wait time, and reducing the risk of acute organ rejection. The bulk of coagulation factors is initially removed from the blood during TPE using albumin and is later replaced with allogeneic plasma. Coagulopathy may develop during TPE and then can persist due to intraoperative blood loss and hemodilution during surgery and cardiopulmonary bypass. We hereby describe the utility of rotational thromboelastometry to assess rapid coagulation changes during TPE and subsequent heart transplant (HT) surgery