Abstract Number: PB0290
Meeting: ISTH 2020 Congress
Background: Unfractionated heparin (UFH) can inhibit the von Willebrand Factor (VWF)-GPIbα interaction in vitro, an anti-thrombotic effect distinct from its anticoagulant role via antithrombin, which may in part explain why unpredictable bleeding complications occur during cardiopulmonary bypass surgery (CPB), when high doses of UFH are used.
Aims: To characterise the changes in VWF antigen (VWF:Ag) activity, function and platelet interaction, that occur pre and post UFH in patients undergoing CPB.
Methods: Following ethics approval and informed consent, samples were taken at baseline, 30 minutes post intravenous UFH, before reversal of UFH with protamine sulphate (PS), 30 minutes after reversal of UFH with PS, 12hrs and 24hrs postoperatively, in a prospective, single centre study, from 30 patients (>18yrs), undergoing first time surgery for the correction of atrial septal defects or tissue mitral valve replacement over a 6 month period.
Results: The mean age of the study group was 58.9yrs (SD±16.1). The VWF:Ag rose significantly by the end of surgery, p< 0.0001. Despite a significant rise in VWF:CBA by the end of surgery (p=0.0133) and 24hrs post-op (p< 0.0001), the VWF:CBA/VWF:Ag fell significantly (p=0.0015) suggesting loss of VWF high molecular weight multimers, presumed due to shear induced proteolysis by the bypass circuit. The VWF Ristocetin Cofactor (VWF:RCo) and VWF:RCo/VWF:Ag both fell but not significantly following UFH (p=0.0588 and 0.0556 respectively). Although the absolute VWF:RCo recovered after UFH reversal with PS (p=0.0003), the VWF:RCo/VWF:Ag did not (p=0.5885).This may reflect reduction in multimer size or the reported inhibitory effect of PS on the VWF-GPIα interaction.
Conclusions: Both heparin and PS affect many components of haemostasis including platelet function and coagulation. The complex interplay between components of haemostasis, well-characterised consumptive and dilutional coagulopathy during CPB as well as these off-target effects of both heparin and PS, make it difficult to predict bleeding reliably in CPB.
To cite this abstract in AMA style:Ranger A, Gaspar M, Elkhatteb A, Fox S, Aw T, Ghori A, Jackson T, Laffan M, Arachchillage D. Haemostatic Markers in Cardiopulmonary Bypass Surgery [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/haemostatic-markers-in-cardiopulmonary-bypass-surgery/. Accessed September 22, 2023.
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