Revisiting acute normovolemic hemodilution and blood transfusion during pediatric cardiac surgery: a prospective observational study

Background: The majority of allogeneic transfusions occur in the perioperative setting, especially during cardiac surgery. In addition to the economic implications, there is emerging evidence that blood transfusion may increase both morbidity and mortality. Acute normovolemic hemodilution (ANH) may limit the need for blood products. Objectives: The primary objective of this study was to determine if the method of blood collection (syringe or bag) during the ANH process impacted the platelet count and function. The secondary objectives included the need for perioperative blood transfusions during the procedure and in the intensive care unit. In addition, we assessed these outcomes' associations with ANH parameters including the method of collection, time of storage, and volume removed. Methods: Data were collected prospectively from 50 patients undergoing cardiac surgery on cardiopulmonary bypass over a 6-month period. Platelet count and function were measured for the ANH blood immediately after collection and again prior to transfusing to the patient at the end of cardiopulmonary bypass. Other data collected included ANH volume, length of storage, and the quantity of all blood products given throughout the perioperative period. Results: No change in platelet count or function was noted regardless of the length of time or collection method for the ANH blood. Twenty-three patients received blood or blood products in the operating room or the intensive care unit, while 27 patients received no blood transfusion during their entire hospitalization. Higher ANH volume (ml·kg⁻¹) and longer storage time were associated with a greater need for intraoperative transfusions. Conclusion: Acute normovolemic hemodilution protects the platelets from the untoward effects of cardiopulmonary bypass and offers an important autologous blood product that improves hemostasis at the conclusion of surgery. Platelet count and function are preserved regardless of the method of collection or the length of storage. The volume of ANH removed appears to be an important determinant of blood product use and further understanding of the impact of this variable is a future direction of upcoming prospective research.