4.2 Leukocyte-Reduced, Washed, Frozen & Rejuvenated RBCs

Leukocyte-Reduced Red Blood Cells

Leukocyte reduction (LR) removes residual white blood cells from a red cell or platelet unit using a specialized filter, most often applied pre-storage (within 24-72 hours of collection, before significant leukocyte fragmentation and cytokine release) rather than post-storage (bedside or laboratory filtration just before transfusion). Pre-storage filtration is now the dominant U.S. practice because it also prevents the accumulation of leukocyte-derived cytokines (IL-1, IL-6, IL-8, TNF-alpha) that build up in the supernatant during storage and that post-storage filtration cannot remove.

AABB Standard: a leukocyte-reduced unit must retain fewer than 5 x 10^6 residual leukocytes per unit (for RBCs and whole blood-derived platelets) while retaining at least 85% of the original red cell content.

Leukoreduction addresses three distinct clinical problems, and the SBB must be able to separate them.

Exam trap: leukoreduction does not prevent transfusion-associated graft-versus-host disease (TA-GVHD). Enough intact, functional T-lymphocytes can survive even below the 5 x 10^6 threshold to engraft in a severely immunocompromised or HLA-matched recipient. Only irradiation reliably prevents TA-GVHD, covered in the next section of this chapter.

Washed Red Blood Cells

Washing replaces a red cell unit's plasma with isotonic saline (with or without a small amount of dextrose), removing plasma proteins, antibodies, potassium, microparticles, and any residual additive solution or glycerol. Because washing opens the closed collection system, the unit becomes a contamination risk and must carry a shortened outdate of 24 hours at 1-6°C (or 4 hours at 20-24°C for platelets), regardless of how much time remained on the original unit.

Primary indications for washed RBCs:

• Severe or recurrent allergic/anaphylactic transfusion reactions that persist despite premedication (antihistamines, antipyretics) and are not resolved by simply slowing the infusion.
• IgA deficiency with documented anti-IgA antibodies and a history of anaphylaxis, when IgA-deficient donor units are not available. Washing is not indicated for asymptomatic IgA-deficient patients without a reaction history — the exam consistently tests this distinction, because washing every IgA-deficient patient's blood is neither necessary nor standard practice.
• Neonatal exchange transfusion and intrauterine transfusion, where washing removes potassium and additive-solution constituents that could be harmful in the very small blood volumes of a fetus or neonate.
• Hyperkalemia risk in patients requiring large-volume or rapid transfusion, since washing removes accumulated supernatant potassium.

Exam trap: washing is not a substitute for leukoreduction and does not reliably prevent TA-GVHD — a washed unit still contains substantial numbers of intact leukocytes unless it was separately leukoreduced or irradiated.

Frozen (Deglycerolized) Red Blood Cells

Frozen storage extends red cell shelf life from weeks to years by adding a cryoprotectant, most commonly glycerol, before freezing. The high-glycerol method (HGM) is the standard U.S. approach: RBCs are glycerolized to a final concentration of approximately 40% (w/v), frozen slowly, and stored at -65°C or colder, permitting storage for up to 10 years. The less common low-glycerol method (LGM) uses about 20% (w/v) glycerol with rapid controlled-rate freezing and ultra-cold storage below -120°C, and is used mainly in specialized or military settings.

Primary uses: long-term storage of rare or autologous units (rare phenotypes, units for alloimmunized patients with multiple antibodies, and directed autologous donations) and strategic or military blood reserves.

Before transfusion, a frozen unit must be thawed and deglycerolized. Glycerol is markedly hypertonic; infusing a glycerolized red cell directly would draw water out of the cell and cause it to crenate, and allowing glycerol to re-enter isotonic plasma too quickly after transfusion would let water rush back into the cell and cause hemolysis. Deglycerolization removes the glycerol gradually through sequential washes of decreasing tonicity — typically hypertonic (12%) saline followed by isotonic (0.9%) saline with dextrose — using an automated cell washer. The final unit must recover at least 80% of the red cells present in the original unit.

Open vs. closed system and outdate — a key SBB distinction:

This mirrors the general storage principle that governs washed RBCs, irradiated components, and pooled products throughout blood banking: opening a sterile system to room air always shortens the outdate to protect against bacterial contamination, and only a validated, sterile closed-system device can preserve a longer post-processing shelf life.

Rejuvenated Red Blood Cells

Rejuvenation uses an FDA-approved rejuvenating solution incubated with red cells to restore or increase 2,3-DPG and ATP that were depleted during liquid storage. Rejuvenation can be applied to units nearing or at outdate — for example, CPD units at up to 24 days, CPDA-1 units at up to 38 days, or AS-1 units at up to 42 days of storage — bringing 2,3-DPG and ATP back to normal or supranormal levels.

Rejuvenation has two distinct downstream paths, and the SBB must know both.

1. Rejuvenate, then wash, then transfuse immediately — because rejuvenation solution itself must be removed before infusion, the rejuvenated unit becomes an open-system washed product with the same 24-hour, 1-6°C outdate described above.
2. Rejuvenate, then glycerolize and freeze — this is the more common strategic use: rejuvenating a unit just before it would otherwise expire rescues it for long-term frozen storage (up to 10 years) with restored oxygen-carrying function, rather than discarding it at outdate.

Exam trap: rejuvenation restores 2,3-DPG/ATP function; it does not extend the liquid (unfrozen) shelf life of a unit on its own, does not remove leukocytes, and does not replace irradiation for TA-GVHD prevention. It is a biochemical/metabolic intervention, not a sterility or immunologic one.