Hemorrhagic complications remain a major concern in patients with cardiogenic shock and extracorporeal cardiopulmonary resuscitation. The purpose of this study was to assess the effect of withholding a bolus of unfractionated heparin (UFH) during emergent cannulation of the peripheral venoarterial extracorporeal membrane oxygenator (VA-ECMO) on initial coagulation parameters, and its association with bleeding and thrombotic complications.

Retrospective, single-center, observational study.

Adult patients undergoing emergent peripheral VA-ECMO were stratified by receipt of an intravenous UFH bolus at the time of cannulation. Then, systemic UFH perfusion was initiated unless contraindicated.

A total of 59 patients were included in the analysis between 2020 and 2024. Mean activated partial thromboplastin time did not differ between groups, with comparable proportions of values within the therapeutic range (15.2% in the bolus group v 13.3% in the nonbolus group; p = 0.776). Major bleeding (Bleeding Academic Research Consortium classification ≥3) within the first 24 hours was more frequent in the UFH bolus group (42.9% v 25.0%) and was associated with a greater need for red blood cell transfusions (median 4 v 2 units; p = 0.003). Multivariate analysis showed similar trends (adjusted odds ratio: 2.26; p = 0.311). Thrombotic event rates were similar between groups (14.3% v 16.7%; p = 0.803), and no device-related thrombosis was observed.

Withholding the UFH bolus during VA-ECMO cannulation results in comparable postimplantation activated partial thromboplastin time values and may reduce early bleeding without increasing thrombotic complications. This limited heparin exposure strategy appears safe and warrants further evaluation in randomized controlled studies.