Single Needle Option: An Alternative to Dual-Needle Access in Erythrocytapheresis in Patients with Sickle Cell Disease
Authors: Munson Teresa , Zhao Jun , Knapp Esther Elise , Du Toit Charmaine , Raj Ashok , McGowan Kerry 
Published: November 2021

Abstract
Background: Erythrocytapheresis or red cell exchange (RCE) is an invaluable treatment option for patients with complications related sickle cell disease, including acute stroke, stroke prevention, acute chest syndrome, and recurrent pain crisis. The procedure entails the removal of each patient's red blood cells containing the abnormal sickle hemoglobin and replacing them with normal red blood cells carrying non-sickled hemoglobin. Adequate vascular access is essential for erythrocytapheresis to allow for high flow rates and various forms of access are used including peripheral veins and central venous access devices. Our center typically uses a single vortex port (Angiodynamics, Walnut Creek, CA) with placement of a peripheral IV at time of procedure in order to maintain a circuit for exchange. Using peripheral access reliably becomes particularly difficult in young patients and those that require multiple access over time due to scaring. To ensure a successful procedure in patients with poor peripheral access, a single-needle (SN) option for TPE (SN-TPE) that is available on Spectra Optia (Terumo BCT, Lakewood, CO) was used. The single-needle procedure utilizes intermittent, rather than continuous, flow, and thus requires extra procedure run time. One discontinuous cycle consists of "exchanging red cells," which is the drawing of blood and removal of the red cells, and "adjusting the volume in the reservoir," which is the returning of blood. These cycles continue until the procedure is complete. This procedure allows us to continue RCE in a select number of patients with poor vascular access.
Methods: We evaluated our institutional experience on patients treated using single-needle RCE. In addition, information regarding each RCE session was collected including duration of procedure and inlet flow rate.
Results: An average of 45 RCE procedures are performed each month. Patients are scheduled every 3 to 8 weeks, with an average of every 4-5 week frequency. We started the Single Needle option in July of 2019 on 3 patients: one adult aged patient and 2 pediatric patients. By the end of 2019 we had perform a total of 27 SN procedures. In 2020, we performed a total of 112 SN procedures, average of 9 procedures each month. As of the first 6 months of 2021, we have completed 35 SN procedures, averages 6 a month.
In patients undergoing single needle exchange we were able to increase inlet flow rates from an average of 30-50ml/min to 60-80ml/min. This decreased the duration of run times from 120-198 min to 77- 119 min. Pre and post hemoglobin S% was comparable between dual and single exchange patients and there was no change in the interval between RCE sessions. Conclusion: With our increasing experience with single-needle RCE, our findings suggest that RCE can be successfully completed using the single-needle option with no impact on pre- and post-exchange hemoglobin S% levels. There was a reduction in the total length of procedure due to ability to maintain higher inlet rates and decreased time to obtain access for RCE. The single needle option also improved patient satisfaction due to more reliable access and negating need for peripheral IV access.

Disclosures
Munson: Terumo Medical Corporation: Consultancy, Honoraria, Speakers Bureau. Raj: Forma therapeutics: Consultancy; Terumo Medical Corporation: Honoraria, Speakers Bureau; Global biotherapeutics: Speakers Bureau.