Effects of Acute Normovolemic Hemodilution on Post-Cardiopulmonary Bypass Coagulation Tests and Allogeneic Blood Transfusion in Thoracic Aortic Repair Surgery: An Observational Cohort Study

Abstract

Background and Aim: Perioperative blood transfusion is associated with increased morbidity and mortality. Acute normovolemic hemodilution (ANH) is a blood conservation strategy associated with variable success, and rarely studied in more complex cardiac procedures. The study aim was to evaluate whether acute ANH improves coagulopathy and reduces blood transfusions in thoracic aortic surgeries. Methods: Single-center observational cohort study comparing ANH and standard institutional practice in patients who underwent thoracic aortic repair from 2019 to 2021. Results: 89 patients underwent ANH and 116 standard practice. There were no significant differences between the groups in terms of demographic or major perioperative characteristics. In the ANH group coagulation tests before and after transfusion of autologous blood showed decreased INR and increased platelets, fibrinogen, all with p<0.0005. Coagulation results in the ANH and control groups were not statistically different. The average number of transfused allogeneic products per patient was lower in the ANH vs control group: FFP 1.1 +/-1.6 vs 1.9 +/-2.3 (p=0.003), platelets 0.6 +/-0.8 vs 1.2 +/-1.3 (p=0.0008), and cryoprecipitate 0.3 +/-0.7 vs 0.7 +/-1.1 (p=0.008). Reduction in RBC transfusion was not statistically significant. The percentage of patients who received any transfusion was 53.9% in ANH and 59.5% in the control group (p=0.42). There was no significant difference in major adverse outcomes. Conclusions: ANH is a safe blood conservation strategy for surgical repairs of the thoracic aorta. Laboratory data suggests that ANH can improve coagulopathy after separation from CPB, and significantly reduce the number of transfused FFP, platelets and cryoprecipitate.