Washed RBCs

Washed Red Blood Cells, a modification performed on standard RBC units to remove the majority of the plasma and its constituents

What Are Washed Red Blood Cells?

Definition: Washed Red Blood Cells are RBC units that have undergone a procedure involving sequential additions of sterile isotonic saline (0.9% NaCl) followed by centrifugation and removal of the supernatant saline/plasma mixture. The final product consists of red blood cells suspended primarily in saline
Goal: To remove as much of the original plasma (and/or additive solution) as possible from the RBC unit

A unit of standard Red Blood Cells (usually Leukoreduced) is selected
Using an automated cell washer or manual methods (less common), sterile 0.9% saline is added to the unit
The unit is mixed and then centrifuged
The supernatant fluid (saline mixed with the original plasma/additive solution) is expressed off and discarded
Steps 2-4 are repeated multiple times (typically 2-3 wash cycles) to achieve significant removal of the original supernatant
After the final wash, the RBCs are resuspended in a small volume of sterile 0.9% saline
Critical Point This process typically involves connecting bags and tubing, often creating an “open system” which breaches the original sterility of the unit

Washing is performed for specific clinical situations where the plasma component of the RBC unit is problematic for the recipient:

Prevention of Severe Allergic Transfusion Reactions: This is the primary indication
- Patients with a history of recurrent, severe allergic reactions (e.g., anaphylaxis, severe urticaria, bronchospasm) attributed to plasma proteins in transfused blood
- Specifically indicated for patients with IgA deficiency who have clinically significant anti-IgA antibodies. Transfusing plasma containing IgA into these patients can trigger severe anaphylactic reactions. Washing removes the vast majority of IgA from the unit
Prevention of Hyperkalemic Complications from Transfusion
- Stored RBCs leak potassium (K+) into the supernatant. Older units can have very high supernatant K+ levels
- Washing removes this high-potassium supernatant
- Indicated for patients at high risk for adverse effects of a potassium load, such as:
  - Neonates (especially premature infants receiving large-volume or exchange transfusions)
  - Patients with pre-existing hyperkalemia or severe renal impairment undergoing large-volume or rapid transfusions
- Note: Using fresh RBCs (e.g., <7-10 days old) is often an alternative strategy to minimize potassium load

This is a major limitation of washed RBCs:

Storage Temperature: 1°C to 6°C (same as standard RBCs)
Expiration: Due to the washing process typically being performed in an open system, the risk of bacterial contamination is increased. Therefore, the expiration date is significantly shortened:
- 24 hours: from the time the washing procedure is completed (when stored at 1-6°C)

Compared to standard RBC units, washed RBCs have:

Minimal Plasma: Most plasma proteins (including IgA, other antibodies, cytokines) are removed
Minimal Additive Solution: Any AS solution is also washed away
Reduced Potassium: Accumulated extracellular potassium is removed
Reduced Leukocytes & Platelets: The washing process also removes residual WBCs and platelets (though pre-storage leukoreduction is usually performed initially anyway)
Slight RBC Loss: The washing process inevitably causes some loss of red blood cells (typically around 10-20%)

Compatibility: Standard ABO/Rh typing and crossmatch procedures are required
Filtration: Administer through a standard blood filter (170-260 microns)
Infusion Time: Must be completed within 4 hours of spiking the bag or removal from controlled 1-6°C storage (and well within the 24-hour post-wash expiration)

Prevents Severe Allergic Reactions: Effectively removes plasma proteins responsible for anaphylaxis (especially IgA)
Reduces Potassium Load: Removes accumulated potassium, safer for susceptible patients receiving large/rapid transfusions
Removes Other Plasma Constituents: Can remove donor antibodies or cytokines (though leukoreduction is more targeted for cytokine removal)

Short Expiration (24 hours): Major logistical challenge, requires washing close to the time of anticipated transfusion, increases wastage if not used
Open System Risk: Potential for bacterial contamination during processing
Time-Consuming & Labor-Intensive: Requires specialized equipment and staff time (approx. 30-60 minutes per unit)
Costly: Adds significant cost compared to standard RBC units
RBC Loss: Reduces the effective dose of RBCs delivered

For preventing allergic reactions in IgA deficient patients with anti-IgA: Using blood products from IgA deficient donors (very rare and difficult to source)
For reducing potassium load: Using fresh RBC units (<7-10 days old)

Washing: Process of removing plasma/supernatant from cellular components using saline exchange
Supernatant: The liquid portion surrounding the cells in a blood component unit
IgA Deficiency: Condition where an individual lacks Immunoglobulin A
Anti-IgA: Antibodies against IgA, found in some IgA-deficient individuals, capable of causing anaphylaxis upon exposure to IgA
Hyperkalemia: High levels of potassium in the blood
Open System: Processing method where the sterility of the component may be compromised, leading to shortened expiration
Automated Cell Washer: Equipment used to perform the washing procedure efficiently