(P-TA-1) Less Is Sometimes More: Low Volume Depletion for Isovolemic Hemodilution Red Blood Cell Exchange as an Effective and Safe Strategy in Sickle Cell Disease

Background/Case Studies: Automated red blood cell exchange (RBCx) is the suggested modality for efficiently reducing hemoglobin S percentage (HbS%), preventing cerebrovascular accidents (CVA) and reducing iron overload in sickle cell disease (SCD) patients. Isovolemic hemodilution RBCx (IHD-RBCx), is a modified RBCx procedure that has been shown to reduce the number of red blood cell (RBC) units required for exchange. However, the transient drop in volume and hematocrit at the start of the procedure can potentially result in hypotension or ischemic injury. This study demonstrates the safety and efficacy of IHD-RBCx using low volume depletion.

Study

Design/Methods: A retrospective chart review of 27 SCD patients undergoing chronic IHD-RBCx was conducted for a single tertiary care center over a 4-year period (04/2019 to 04/2023). Procedures were performed every 6-8 weeks on a Spectra Optia Apheresis System. Data points collected included age, gender, history of CVA or acute chest syndrome (ACS), total number of IHD-RBCx procedures performed, procedure-related complications, hospitalizations, ferritin level, RBC alloimmunization, and HbS%. The RBC depletion volumes and the number of RBC units required were calculated using the TerumoBCT RBCx calculation tool.

Results/Findings: Of the 27 SCD patients (median age: 27 years; M= 7, F= 20), 14 patients had a history of CVA and 15 had a history of ACS. A total of 319 IHD-RBCx procedures were performed (range: 2-24 procedures per patient). 7 of 319 procedures experienced complications: 2 hypotensive events, 1 chest pain, 1 nausea/vomiting, 2 transfusion reactions, and 1 generalized body pain. No patients were hospitalized due to CVA, ACS, or any major ischemic event over the 4-year period. 1 patient demonstrated RBC alloimmunization following IHD-RBCx procedure, and 18 patients showed a reduction in ferritin compared to pre-IHD-RBCx levels. The median pre-procedure HbS% was 49.5, and the median post-procedure HbS% was 11.7. When reviewing the final procedure from each patient, the median RBC depletion volume was 80 ml (range: 47ml- 175ml) with a median of 1 RBC unit saved per procedure (mean: 0.63 RBC units).

Conclusions: IHD-RBCx with low volume depletion is a safe and effective method for reducing the HbS% in patients with SCD while reducing ferritin levels and patient exposure to RBC products. However, data on concurrent iron overload therapy was not collected and large prospective studies are required to further define the benefits of IHD-RBCx using low volume depletion.

Importance of research: To date, this is the largest cohort of sickle cell disease patients at a single institution undergoing isovolemic hemodilution RBC exchange (IHD-RBCx) using low volume depletion. These analyses show that IHD-RBCx using low volume depletion is safe and effective at reducing the HbS% to satisfactory levels while reducing patients’ ferratin levels overtime and exposure to blood products.