(P-TS-63) Isovolumic Hemodilution Red Blood Cell Exchange in Sickle Cell Disease: A Single Center Experience.

Isovolumic hemodilution red cell exchange (IHD RCE) is a modified form of standard red cell exchange (SRD RCE) intended to reduce packed cell units (PRBC) or reduce the frequency of exchange in patients with Sickle Cell Disease (SCD). This retrospective analysis of 83 patients aims to add to the limited existing literature on IHD-RCE and to show long-term effectiveness.

Study

Design/Methods:

This is a single-centre retrospective study. We implemented the IHD RCE strategy using SPECTRA OPTIA in mid 2021 (during COVID-19 pandemic to effectively manage blood shortage) for patients with SCD on RCE. We aimed to decrease the number of PRBC units used, rather than increasing time interval between sessions. IHD was accomplished by reducing the HCT by 4% from baseline during first 15 minutes and replacing it with 0.9% NaCl. After achieving target hemodilution the pRBC exchange phase was begun with an end target HCT set to baseline HCT. Due to anticipated reduction in the need for pRBC with IHD, all patients initially received approximate 25% decrease in pRBC units. This was adjusted as needed.

All patients who were on RCE from January 2021 to March 2024 were included. Along with age, sex, and genotype data, hemoglobin electrophoresis data (both pre- and post-RCE) were collected for two consecutive RCE sessions at 3 separate time points: The first half of 2021 (Will be referred as Pre-IHD), Second-half of 2021 (just after implementing IHD RCE strategy; Post-IHD1) and early 2024 (2.5 years after Post-IHD1; Post-IHD2). We analyzed two domains; 1) Fraction of cells remaining (FCR) and 2) Mean number of PRBC units used. We applied a linear mixed effects model with repeated measures to analyze the above metrics using the Imer function in Imer 4R package.

Results/Findings: Total 84 patients were on RCE during the entire study duration. One patient who was on dialysis and had pulmonary fibrosis did not tolerate IHD RCE. Among 83 patients included in final analysis, median age was 38 years (IQR = 29- 46.5), 53 were females (63.8%) and majority had HbSS genotype (n=77, 87.95%), followed by HBSC (n=7) and HbSb0 (n=2). Pre-IHD FCR was 33.4±1.09%, It increased by 4.96±1.12% post-IHD1 compared to pre-IHD values (P < 0.001). Post-IHD2 FCR (1.53±1.12%) was not significantly different than Pre-IHD (P=0.175). Pre-IHD, mean number of PRBC units used/patient/exchange session was 6.91±0.011. This was decreased by 1.63±0.08 units post-IHD1 and by 1.25±0.08 units post-IHD2 (p= < 0.001).

Conclusions: This single-centre retrospective study demonstrated the sustainability of IHD over 2.5 years. While some patients required an increase in the number of PRBC units used at initiation, we demonstrated a durable 18.5% reduction in number of PRBC units used without any significant change in FCR at 2.5 years.