Blood Conservation Strategies in Adult Sickle Cell Patients on Chronic Transfusion Therapy: A Single Center Experience
Authors: Jones Jennifer M , Swett Ariel , Lawrence Courtney Elizabeth , Bloch Evan , Lanzkron Sophie M. 
Published: November 2021

Abstract

Background: Adult sickle cell patients on chronic transfusion therapy (CTT) garnered special concern during the COVID-19 pandemic, when mass cancellation of blood drives threatened the national blood supply. In response, the American Society of Hematology proposed several strategies to decrease blood utilization, while maintaining adequate disease control for sickle cell patients on CTT. These included targeting a higher end hemoglobin S%, switching patients to simple transfusions when appropriate, and transitioning to alternative disease modifying therapies. There is little evidence to support the safety of altering exchange therapy regimens. Accordingly, at the Johns Hopkins Sickle Cell Center for Adults, a multidisciplinary team of clinicians and transfusion medicine specialists evaluated patients on a case by case basis to determine how their exchanges could be modified to accommodate for anticipated blood supply shortages. We describe our blood conservation efforts during the COVID-19 pandemic and resulting clinical outcomes for adult patients with sickle cell anemia (SCA).
Methods: For inclusion in this IRB-approved retrospective study, patients received at least 7 monthly exchange transfusions between March 2019 and February 2020 and continued care through March 2021. Decisions regarding CTT were made prior to data collection. Modifications to chronic exchanges included increasing the fraction of cells remaining (FCR), decreasing the end hematocrit, or switching to a hemodilution method. Additionally, select patients transitioned to monthly simple transfusions if they were clinically stable, had a hemoglobin ≤ 7 g/dL, and had a persistently suppressed hemoglobin S% (≤ 30).
We collected basic demographics, pre-exchange laboratory studies, and exchange parameters before and after each transfusion encounter in the year before (March 2019 - February 2020) and during (March 2020 - February 2021) the COVID-19 pandemic. Lastly, we recorded presentations to urgent care and the emergency department; and hospital admissions during each time period. We reported descriptive statistics for the cohort and compared outcomes using the Wilcoxon signed-rank test and Mann Whitney U test. We analyzed data using Stata/SE Version 16.1.
Results: We identified 58 patients with SCA who qualified for inclusion (Table 1). Fifty-three patients remained on chronic exchange transfusions during the pandemic, and five were switched to simple transfusions. For patients who remained on chronic exchanges, most received conventional automated red cell exchange (RCE) prior to (85%) and during the pandemic (77%). Use of hemodilution increased (15% to 23% of patients). Forty-three patients experienced an increase in mean FCR (33.6 (SD 11.6) vs 37.7 (4.7), p = .00). Of those, 22 patients saw a concomitant decrease in mean end hematocrit (30.8 (1.7) vs 29.6 (1.1), p = .00). These changes resulted in a decline in the average number of units per procedure (8.6 (1.9) vs 7.3 (1.7), p = .00), which corresponded to 890 units conserved. Mean pre-transfusion hemoglobin values declined (9.4 (1.3) vs 9.2 (1.3), p = 0.01), but hemoglobin S%, reticulocyte count, and ferritin values were unchanged (p &gt; 0.05). Acute care presentations and hospital admissions declined, which were likely spurred by concerns about COVID-19 infection (Table 2, p &lt; 0.05).
During the pandemic, three patients died, one of whom had been switched to simple transfusions. This patient experienced a consistent rise in hemoglobin S% until death. Two of the remaining patients on simple transfusions were switched back to automated RCE due to an increase in hemoglobin S% above goal (Figure 1).
Conclusions: During the COVID-19 pandemic, we conserved red blood cell units through expanded use of hemodilution, higher FCR values, and switching some patients to simple transfusions. Patients who remained on exchanges maintained hemoglobin S% values near a goal of 30% without increasing iron burden. In contrast, the majority of patients who were switched to simple transfusions were unable to maintain goal hematologic parameters, and one patient died. Our data suggest that in a blood shortage crisis, changing the exchange procedure itself may be the safest means of conserving blood in a population of adult sickle cell patients; however longer follow-up is needed to ensure that these changes are safe.
Figure 1 Figure 1.

Disclosures
Lanzkron: GBT: Research Funding; Shire: Research Funding; Novo Nordisk: Consultancy; CSL Behring: Research Funding; Pfizer: Current holder of individual stocks in a privately-held company; Teva: Current holder of individual stocks in a privately-held company; Novartis: Research Funding; Imara: Research Funding; Bluebird Bio: Consultancy.