Heparin-induced thrombocytopenia in extracorporeal membrane oxygenation-supported patients: a systematic review and meta-analysis.

Background: In recent years, extracorporeal membrane oxygenation (ECMO) has been increasingly used in critically ill patients with respiratory or cardiac failure. Heparin is usually used as anticoagulation therapy during ECMO support. However, heparin-induced thrombocytopenia (HIT) in ECMO-supported patients, which results in considerable morbidity and mortality, has not yet been well described. This meta-analysis and systematic review aimed to thoroughly report the incidence of HIT on ECMO, as well as the characteristics and outcomes of HIT patients.

Methods: We searched the PubMed, Embase, Cochrane Library, and Scopus databases for studies investigating HIT in adult patients supported by ECMO. All studies conforming to the inclusion criteria were screened from 1975 to August 2023. Nineteen studies from a total of 1,625 abstracts were selected. The primary outcomes were the incidence of HIT and suspected HIT.

Results: The pooled incidence of HIT in ECMO-supported patients was 4.2% (95% CI: 2.7-5.6; 18 studies). A total of 15.9% (95% CI: 9.0-22.8; 12 studies) of patients on ECMO were suspected of having HIT. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used immunoassay. The median optical density (OD) of the ELISA in HIT-confirmed patients ranged from 1.08 to 2.10. In most studies, the serotonin release assay (SRA) was performed as a HIT-confirming test. According to the subgroup analysis, the pooled incidence of HIT in ECMO patients was 2.7% in studies whose diagnostic mode was functional assays, which is significantly lower than the incidence in studies in which the patients were diagnosed by immunoassay (14.5%). Argatroban was most commonly used as an alternative anticoagulation agent after the withdrawal of heparin. Among confirmed HIT patients, 45.5% (95% CI: 28.8-62.6) experienced thrombotic events, while 50.1% (95% CI: 24.9-75.4) experienced bleeding events. Overall, 46.6% (95% CI: 30.4-63.1) of patients on ECMO with HIT died.

Conclusion: According to our study, the pooled incidence of HIT in ECMO-supported patients is 4.2%, and it contributes to adverse outcomes. Inappropriate diagnostic methods can easily lead to misdiagnosis of HIT. Further research and development of diagnostic algorithms and laboratory assays are warranted.