LAUSR

Learning Objectives: Cardiac surgery using cardiopulmonary bypass (CPB) carries a high risk of bleeding and need for perioperative blood transfusion. Blood transfusion is an expensive, resource-intensive intervention that is associated with increased rates of ICU length of stay, end-organ dysfunction, and mortality. Normovolemic hemodilution is a blood conservation strategy used to reduce transfusion rates that involves replacement of whole blood with fluid to maintain normovolemia. SANGUINATE® (PEGylated Carboxyhemoglobin Bovine) is a novel hemoglobin-based oxygen carrier that is able to deliver oxygen effectively to tissues in the presence of severe hypoxia. Its use as a component of the replacement fluid during hemodilution would provide an additional means to augment tissue oxygen delivery while avoiding perioperative RBC transfusion. In this study simulating normovolemic hemodilution, the effect of varying mixtures of bovine whole blood and SANGUINATE® on flow characteristics and oxygenation during CPB were evaluated. Methods: Six standardized 120-minute CPB runs simulating normovolemic hemodilution using varying proportions of normal saline, bovine whole blood, calcium chloride, heparin, and SANGUINATE® were performed. The first run represented a control with no addition of SANGUINATE®. The circuit was de-aired and heated to normothermia (37°C). The FiO2 was set to 0.60 and the sweep gas was set to 0.5 L/min. The blood was circulated through the CPB circuit at 5 L/min for all runs. Hemoglobin concentration, activated clotting time, and indices of CPB functionality were assessed at regular intervals following the addition of SANGUINATE®. Results: The addition of SANGUINATE® did not result in major changes in CPB flow characteristics as determined by pump RPM, flow rate, or line pressure. Adequacy of oxygenation, as determined by the post-membrane PO2 value, was maintained for all runs irrespective of the SANGUINATE® concentration. No visible clots were identified on the membrane oxygenator following the runs. Conclusions: The results of our study show that SANGUINATE® does not impact the performance of the CPB circuit in a normovolemic hemodilution model using bovine whole blood. Oxygenation remained adequate, and thrombogenicity was not observed. These results support further evaluation of SANGUINATE® as a means to reduce blood transfusion in the perioperative cardiac surgical setting.