The development of extracorporeal life support technology has added a new dimension to the care of critically ill patients who fail conventional treatment options. Extracorporeal membrane oxygenation (ECMO)—specialized temporary life support for patients with severe cardiac or pulmonary failure—plays a role in bridging the time for organ recovery, transplant, or permanent assistance. The overall patient outcome is dependent on the underlying disease, comorbidities, patient reaction to critical illness, and potential adverse events during ECMO. Moreover, the contact of the blood with the large artificial surface of an extracorporeal system circuit triggers complex inflammatory and coagulation responses. These processes may further lead to endothelial injury and disrupted microcirculation with consequent end-organ dysfunction and the development of adverse events like thromboembolism. Therefore, systemic anticoagulation is considered crucial to alleviate the risk of thrombosis and failure of ECMO circuit components. The gold standard and most used anticoagulant during extracorporeal life support is unfractionated heparin, with all its benefits and disadvantages. However, therapeutic anticoagulation of a critically ill patient carries the risk of clinically relevant bleeding with the potential for permanent injury or death. Similarly, thrombotic events may occur. Therefore, different anticoagulation strategies are employed, while the monitoring and the balance of procoagulant and anticoagulatory factors is of immense importance. This narrative review summarizes the most recent considerations on anticoagulation during ECMO support, with a special focus on anticoagulation monitoring and future directions.

Background: The initiation of extracorporeal membrane oxygenation (ECMO) is associated with complex inflammatory and coagulatory processes, raising the need for systemic anticoagulation. The balance of anticoagulatory and procoagulant factors is essential, as therapeutic anticoagulation confers a further risk of potentially life-threatening bleeding. Therefore, our study aims to systematize and analyze the most recent evidence regarding anticoagulation monitoring and the thromboembolic events in patients receiving veno-arterial ECMO support. Methods: Using the PRISMA guidelines, we systematically searched the Scopus and PubMed databases up to October 2022. A weighted effects model was employed for the meta-analytic portion of the study. Results: Six studies comprising 1728 patients were included in the final analysis. Unfractionated heparin was used for anticoagulation, with an activated partial thromboplastin time (aPTT) monitoring goal set between 45 and 80 s. The majority of studies aimed to investigate the incidence of adverse events and potential risk factors for thromboembolic and bleeding events. None of the authors found any association of aPTT levels with the occurrence of thromboembolic events. Finally, the most frequent adverse events were hemorrhage (pooled 43%, 95% CI 28.4; 59.5) and any kind of thrombosis (pooled 36%, 95% CI 21.7; 53.7), and more than one-half of patients did not survive to discharge (pooled 54%). Conclusions: Despite the tremendous development of critical care, aPTT-guided systemic anticoagulation is still the standard monitoring tool. We did not find any association of aPTT levels with thrombosis. Further evidence and new trials should clarify the true incidence of thromboembolic events, along with the best anticoagulation and monitoring strategy in veno-arterial ECMO patients.

Background: Extracorporeal membrane oxygenation (ECMO) requires systemic anticoagulation to prevent clotting, typically using unfractionated heparin (UFH). However, anticoagulation carries a bleeding risk, necessitating monitoring. Activated clotting time (ACT) is a commonly used monitoring tool for UFH anticoagulation. However, systematized evidence linking ACT monitoring with haemostatic complications (bleeding and thrombosis) is missing. Methods: A systematic review (Scopus and PubMed, up to 13 July 2024) including studies reporting on the patients receiving ECMO support with UFH anticoagulation monitored using ACT was performed. Results: A total of 3536 publications were identified, of which 30 (2379 patients) were included in the final review. Thirteen studies found no significant association between ACT values and haemorrhage, while four studies suggested a relationship between elevated ACT levels and bleeding events. Eight studies demonstrated no association between ACT values and the occurrence of thrombosis. Major bleeding was most common (49%, 13 studies with 501 events), while the pooled rate of thrombosis was 25% (16 studies with 309 events) and in-hospital mortality was 51% (17 studies, 693/1390 patients). Conclusions: Despite advancements in ECMO, the optimal approach for anticoagulation monitoring remains undefined. Most studies in this review did not establish a significant relationship between ACT levels and haemostatic complications. Based on the current evidence, ACT does not appear to be a reliable tool for monitoring anticoagulation in patients receiving ECMO, and alternative methods should be considered.