Hemorrhagic and thromboembolic complications are common during treatment with extracorporeal membrane oxygenation (ECMO), resulting in considerable morbidity and mortality. This emphasizes the clinical relevance of understanding hemostatic changes occurring during ECMO treatment.
As platelets are key players in hemostasis, detailed knowledge on how ECMO treatment affects platelet function is of great importance. The researchers, therefore, aimed to systematically summarize and discuss existing knowledge on platelet function during ECMO treatment in adult patients.
Systematic review complying with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Objectives and methods were specified in a PROSPERO protocol (ID no CRD42018084059). The MEDLINE/PubMed, EMBASE, and Web of Science databases were systematically searched on September 10, 2018.
Quality assessment tool
A standardized quality assessment tool was used to assess the risk of bias in included studies. The primary outcome was platelet function during ECMO treatment, measured as platelet adhesion, activation or aggregation. Secondary outcomes were thrombosis, bleeding, and mortality during ECMO treatment.
A total of 591 studies were identified, of which seven were eligible for inclusion in the qualitative synthesis. Of these, one study investigated the expression of platelet adhesion receptors and found them to be reduced during ECMO treatment; two studies reported a decrease in platelet activation markers during ECMO treatment; five studies demonstrated reduced platelet aggregation during ECMO treatment.
Three studies reported on thrombosis, mortality and/or bleeding during ECMO treatment; no thromboembolic events were reported; all three studies reported frequent bleeding episodes defined on basis of transfusion requirements. An in-hospital mortality of 35–40% and a 30-day mortality of roughly 30% were reported in three different studies.
Inflammation has been shown to induce bleeding in thrombocytopenic mice. Only one of the included studies provided information regarding inflammatory parameters measured during ECMO treatment; furthermore, the associations between bleeding episodes and platelet count or inflammatory parameters were not accounted for in any of the included studies.
Laine et al. found no significant associations between platelet aggregation and the risk of bleeding or mortality, and no thromboembolic events were reported in any of the included studies; both of which might be attributed to the small cohort sizes.
Whether there is an association between platelet function and clinical complications such as bleeding or thromboembolic events, therefore, remains to be established.
The present systematic review reveals a substantial knowledge gap regarding platelet function during ECMO treatment in adult patients and underscores the demand for more and well-designed studies on this topic.
There is suggested evidence of reduced platelet adhesion, decreased platelet activation, and reduced platelet aggregation in adult patients during ECMO treatment. Importantly, platelet aggregation results need to be interpreted in the light of low platelet counts. The associations of platelet function and bleeding and/or thromboembolic complications during ECMO treatment remain to be fully elucidated.