Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm

    Disease

    Select...

    Specialty

    Select...

    Chief Complaint

    Select...

    Organ System

    Select...

    Patent Pending

    Sickle Cell RBC Exchange Volume

    Estimates the volume of donor RBCs needed for RBC exchange in patients with sickle cell disease.
    Favorite
    When to Use
    Pearls/Pitfalls
    Why Use

    Patients with sickle cell disease complications requiring RBC exchange.

    • Due to frequent exposures to donor RBCs, patients with sickle cell disease are at high risk for developing RBC alloimmunization and many centers require some level of antigen matching.
    • In patients necessitating RBC exchange for an acute complication, if the pre-exchange percent hemoglobin S (HbS%) is unavailable, assuming that it is equal to 100% can be a conservative measure.  
    • Transfused blood for sickle cell patients should be antigen negative for any patient RBC alloantibodies, crossmatch compatible, and sickle negative.
    • This calculation is intended to produce the same hematocrit post-procedure as pre-procedure. Apheresis instruments have on-board calculators to adjust hematocrit according to user-entered preferences, which may necessitate adjustments to RBC replacement volume.
    • Sickle cell disease is associated with a number of complications, including pain crises, acute chest syndrome, and stroke. Automated RBC exchange is an effective therapeutic modality both in the acute treatment of severe sickle cell-related complications and in long-term maintenance.  
    • Calculating the volume of donor RBCs necessary to achieve appropriate reduction in HbS% is useful when ordering blood for RBC exchange procedures.  
    Male
    Female
    in
    lbs
    %
    %
    %
    %

    Result:

    Please fill out required fields.

    Next Steps
    Evidence

    Advice

    The calculated volume of replacement RBCs may be divided by 350 mL to approximate the number of RBC units to order. Adjustments to the patient’s hematocrit may require alterations to these calculations.

    Formula

    RBC replacement volume = RBC volume × ln (HbS, initial / HbS, goal) / donor Hct

    Where RBC volume = total blood volume × patient Hct

    Note: HbS and Hct are in whole % (i.e., 30%, not 0.3). RBC units assume 350 mL per unit and are rounded up to the nearest whole unit.

    Content Contributors
    • Alex Ryder, MD, PhD
    • Caleb Cheng, MD
    • Christopher Tormey, MD
    Content Contributors
    • Alex Ryder, MD, PhD
    • Caleb Cheng, MD
    • Christopher Tormey, MD