From the Guidelines
Higher hemoglobin S (HbS) targets of up to 50% for red blood cell exchange can be considered in select patients to reduce exchange frequency and donor usage without added stroke risk, as suggested by recent guidelines 1. This approach is based on the idea that moderate HbS levels (30-50%) still provide significant protection against vaso-occlusive events compared to untreated levels (>80-90%), while reducing the risks associated with frequent transfusions such as iron overload, alloimmunization, and transfusion reactions. When implementing this strategy, patients should be carefully selected based on their clinical stability, absence of recent complications, and good adherence to treatment, as recommended by the American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support 1. Key considerations include:
- Careful patient selection based on clinical stability and adherence to treatment
- Regular monitoring of HbS levels, complete blood counts, and clinical symptoms
- Individualization of targets, with more conservative targets maintained for patients with history of stroke or severe disease manifestations, as suggested by guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attack 1. The exchange procedure remains the same technically, but the interval between exchanges may be extended from every 4-6 weeks to every 6-8 weeks, depending on the patient's response and clinical stability, as part of a comprehensive transfusion support plan 1.
From the Research
Red Blood Cell Exchange Targets
- Some centers are trialing higher HbS targets (≤50% in select patients) to reduce exchange frequency and donor usage, without added stroke risk 2.
- A study found that maintaining an HbS target of <50% in patients with a low risk of stroke did not increase the risk of cerebrovascular accidents (CVA) 2.
- The study suggested that liberalizing the HbS target could confer clinical flexibility without increasing the risk of CVA in a selective population 2.
Association Between Post-Transfusion Hemoglobin S Level and Pre-Transfusion Hemoglobin S Level
- A retrospective study found that targeting post-HbS ≤10% was associated with higher odds of having events of F/u-HbS <30% between monthly treatments 3.
- The study also found that targeting post-HbS ≤15% was associated with higher odds of events of F/u-HbS <40% 3.
Red Blood Cell Exchange Procedures
- Red blood cell exchange (RBCEx) is frequently used in the management of patients with sickle cell disease (SCD) and acute chest syndrome or stroke, or to maintain target hemoglobin S (HbS) levels 4.
- A case series explored the utility of using the daily "rate of rise" (RoR) in HbS to manage RBC depletion/exchange treatment in SCD 5.
- The study found that the RoR in HbS varied widely between patients but remained relatively stable within individuals, and was not significantly influenced by changes in post-procedure Hct or concurrent hydroxyurea use 5.
Standard Operating Procedure for Isovolemic Hemodilution-Red Cell Exchange
- A standard operating procedure for Isovolemic Hemodilution-Red Blood Cell Exchange (IHD-RBCx) has been described, which is a two-step modification of the conventional RBCx with several advantages, including cost reduction 6.