Heparin Monitoring with an Anti-Xa Protocol Compared to Activated Clotting Time in Patients on Temporary Mechanical Circulatory Support.

Background: Temporary mechanical circulatory support (tMCS) devices are used for patients with severe cardiac or respiratory failure; however, these patients are at high risk for clotting and bleeding. The best method to monitor heparin in these patients has not been established.
Objective: To determine the risks for bleeding and clotting while monitoring heparin with either anti-Xa or activated clotting time (ACT) in tMCS patients.
Methods: A retrospective cohort study was conducted on tMCS patients who received heparin adjusted according to an anti-Xa or ACT protocol. The primary outcome was incidence of major bleeding. Pertinent secondary outcomes were individual components of the primary outcome, clotting events, and time to therapeutic range.
Results: There were 103 patients included in the study: 53 in the ACT group and 50 in the anti-Xa group. Overall, there were 30 (56.6%) patients with major bleeding in the ACT group, compared with 16 (32%) patients in the anti-Xa group ( P = 0.017). An anti-Xa-based protocol was associated with a decreased hazard of major bleeding (hazard ratio = 0.388 [0.215-0.701]; P = 0.002) in the univariate analysis. In the multivariable analysis, an anti-Xa protocol remained associated with a significantly lower hazard of bleeding. Findings were similar when broken down into more discrete subgroups of the entire cohort, extracorporeal membrane oxygenation life support (ECMO), and non-ECMO groups.
Conclusion and Relevance: Anti-Xa monitoring was associated with a lower hazard of bleeding during tMCS compared to an ACT-based protocol. Further studies should evaluate if anti-Xa monitoring should be preferentially used in tMCS.