Purified VWF Corrects Dysfunctional Primary Hemostasis in Patients with Extracorporeal Life Support. in Vitro Studies Against Cryoprecipitate

INTRODUCTION. Extracorporeal membrane oxygenation (ECMO) is a mechanical assistance system used to temporarily support patients with life-threatening cardiac and/or respiratory dysfunction when traditional treatment fails. Bleeding is one of the main complications causing significant morbidity and mortality. Development of acquired von Willebrand disease (AVWD) within 1-6 hours after ECMO implantation has been described, with recovery 3-24 hours after device explant. There is no consensus on the most suitable treatment for these patients.

OBJECTIVE.To investigate the improvement in primary hemostasis after the in vitro addition of VWF-containing concentrates in samples from patients with ECMO.

MATERIAL AND METHODS:During 2023, 7 adults with ECMO (n=2 venous-venous, and n=5 veno-arterial) due to pulmonary or cardiovascular diseases were included in the study. Samples were collected within the first 72 hours after implantation and 5 days after removal (n=16 samples).Hematocrit, platelet counts, and ADAMTS13 activity, by FRETS assay, were determined.Platelet function was evaluated by PFA-200 ( Siemens Healthineers®) with collagen-epinephrine and collagen-ADP cartridges, and platelet aggregation with ristocetin 1 mg/mL ( Helena BioSciences APACT4 ®). VWF function was assessed by antigen (VWF:Ag), activity (VWF:GPIbM), and VIII factor (VIIIF) quantification ( Siemens Atellica COAG360®), collagen (VWF:CB) and VIIIF binding (VWF:VIIIF) to VWF ( Asserachrom ®and Thermo Scientific MultiSkan FC ®) and VWF multimeric analysis (agarose gels and immunoblotting). Total-TAS ®( Zacros) was used to analyze hemostasis before and after in vitro addition of VWF concentrate ( Haemate-P ® ) or cryoprecipitate (Cp) in each sample. The cohort was divided into two groups according to the time when the samples were collected. Only the subjects showing a correction of the occlusion times at Total-TAS® were included in the comparative analysis.

RESULTS.Mucocutaneous bleeding and pulmonary embolism were reported in n=3.One patient died before device removal. Within the first 72 hours after implantation PFA-200 was prolonged (>300s), VWF:Ag, VWF:GPIbM, and VWF:CB values increased, and hematocrit, platelet counts, ristocetin aggregation and VWF:VIIIFdecreased, as reported in Table 1.VIIIF was within normal range. Loss of high molecular weight VWF multimers was observed in all samples, and VWF:GPIbM/VWF:Ag ratio was <0.70 in 29% patients. These findings persisted within 5 days after removal, except for PFA-200 and platelet counts that normalized in 29% and 50%, respectively, while VIIIF values increased. In the samples collected after ECMO removal, the addition of Haemate-P® significantly reduced Total-TAS ® occlusion times (573.00±280.91 vs 821.20±586.54 p=0.043, post- vs pre-). Correction of the occlusion time with Cp was not statistically significant. The hemostatic effect of Haemate-P® was superior to Cp (790.80 ± 582.02, p=0.043). No differences were observed between basal values and the addition of neither Haemate-P ® nor Cp in samples collected during ECMO, Figure 1.

CONCLUSIONS.Treatment with ECMO alters primary hemostasis in association with AVWD. In our cohort, these effects were seen early after implantation and, at least, up to 5 days after device removal. Most patients requiring ECMO treatment exhibit a complex medical history and are exposed to multiple drugs affecting numerous analytical values, making the interpretation of primary hemostasis complicated. The addition of Haemate-P ® in vitro significantly improved the hemostatic efficiency compared to Cp only when ECMO was discontinued. More studies are needed to evaluate the role of VWF-containing concentrates in the treatment of these patients, being Total-TAS ® a potentially useful mechanism to investigate it.

GRANTS: López-Borrasca Scholarship funded by FETH/SETH, with the collaboration of CSL Behring (Spain) and Zacros (Fujimori Kogyo Co, Ltd, Japan), and 2021-SGR-01118, Agencia de Gestió de Ajuts Universitaris i de Recerca (AGAUR), Generalitat de Catalunya.