Patients undergoing major heart and vascular surgery are often in need of intraoperative and/or postoperative anticoagulation. To ensure the appropriate blood concentration of anticoagulants and reduce the risk of adverse events, anticoagulation monitoring is crucial. In contrast, due to contact of blood with artificial surfaces, some patients develop hyperinflammation which may increase the risk of thrombosis.
Patients undergoing heart surgery require full heparinization before the start of the heart-lung machine, which is later reversed using protamine. The levels of anticoagulation are intraoperatively monitored with activated clotting time (ACT). In the postoperative period, the monitoring of rest-heparinization or rebound effect is further performed. In certain cases, the addition of protamine is needed, based on the available monitoring tests. The postoperative monitoring of anticoagulation is usually performed using ACT and activated partial thromboplastin time (aPTT), and may be extended by other diagnostic methods, including viscoelastic tests. Moreover, to ensure the hemostatic capacity of the patient, monitoring of other parameters (platelet count, fibrinogen concentration, prothrombin time quick assay (PT), antithrombin level, etc.) may be included. Finally, in the case of patients receiving extracorporeal life support (ECMO), continuous anticoagulation is indicated, and its monitoring is of immense importance.
Furthermore, in the case of vascular surgery, patients require unfractionated heparin (UFH) intraoperatively, including postoperative continuous infusion.
The evidence on correlation and available monitoring tools is scarce and contradictory, usually based on retrospective analyses of patients´ data from medical charts. Additionally, the role of inflammation in the development of delirium is still unclear, and this association is a subject of debate.
Well-known consequences of postoperative delirium (POD) include poor functional outcome with increased morbidity and mortality, and increased healthcare costs due to institutionalization and rehospitalization. The incidence of POD after cardiac and vascular surgery remains between 13 and 52%. The current hypothesis on the pathophysiology of POD includes disruption of the blood-brain barrier allowing peripheral inflammation and mediators to cause neuro-inflammation. Neurotoxicity induced by a disbalance of pro- and anti-inflammatory mediators and oxidative stress might explain neuronal damage and neurotransmitter disbalance responsible for POD. To improve patients´ functional outcome and the financial burden of POD there is a growing interest in identifying predictive and diagnostic (bio-)markers. The neurofilament light chain (NfL) protein has shown promising results as a potential biomarker for POD. However, the literature on cardiac and vascular patients is limited.
