With interest we have read the systematic review by Eshmuminov et al. regarding porcine and human liver normothermic machine perfusion (NMP) . The authors focused on studies using red blood cells (RBC) as oxygen carrier in the perfusion fluid and excluded studies using perfusion solutions based on artificial oxygen carriers. In their review, the authors state "We excluded studies using artificial oxygen carriers. Results of studies with synthetic hemoglobin based oxygen carriers (HBOC) were disappointing, even with stopping of the ongoing clinical trials by FDA due to safety reasons". This article is protected by copyright. All rights reserved.