From Pandemic to Practice: How COVID-19 Has Reshaped Haemostasis in Cardiac Surgery: A Narrative Review

The utilisation of cardiopulmonary bypass (CPB) during cardiac surgery is often associated with complex haemostatic perturbations, frequently manifesting as a paradoxical risk of both bleeding and thrombosis. This is postulated to be driven by systemic inflammation, endothelial activation and contact activation of the coagulation cascade due to extracorporeal circulation. However, the coronavirus disease 2019 (COVID-19) pandemic revealed a unique hypercoagulable state, termed COVID-19-associated coagulopathy (CAC), also observed in those vaccinated against COVID-19. CAC displays similar physiological manifestations to those of disseminated intravascular coagulation (DIC), characterised by elevated fibrinogen and D-dimer values. The precise pathogenesis of CAC requires further elucidation though proposed mechanisms include: an exaggerated inflammatory response to COVID-19 infection or antibody proliferation due to vaccination, direct epithelial cell damage mediated by angiotensin converting enzyme 2, and 'hypoxithrombosis'. CAC has since provided a unique framework to understand and potentially mitigate coagulation complications encountered during CPB in the post-pandemic era, as it is no longer sufficient to view COVID-19 as a transient influence on surgical risk. Rather, it must be recognized as a persistent modifier of the haemostatic environment across the population, with direct implications upon patient selection, intraoperative management and postoperative care in cardiac surgery. This review examines the pathological drivers behind CAC alongside the insights obtained from CAC management during ECMO deployment, to investigate the potential translation of such knowledge into improved anticoagulation strategies and monitoring during cardiac surgery. The use of alternative anticoagulants including factor XI inhibitors and the modulation of heparinase activity offers promising avenues to attenuate coagulopathies more commonly observed during CPB in the post-pandemic climate, whilst anti-Xa assays and viscoelastic testing have offered applicability to modern perfusion practices. By bridging the knowledge gained during the pandemic with that of conventional CPB, this review aims to inform future strategies for haemostasis management in cardiac surgery in a novel cohort of surgical patients.