11.2 Blood Component Preparation, Storage, Expiration, and Indications for Transfusion

Blood Component Preparation, Storage, Expiration, and Indications for Transfusion

Modern transfusion medicine is founded on the paradigm of component therapy—fractionating a single unit of whole blood into its constituent cellular and plasma derivatives. Transfusing specific components provides targeted therapeutic efficacy, avoids unnecessary circulatory volume overload, and allows one voluntary donor to save multiple patient lives. For medical technologists, rigorous adherence to differential centrifugation parameters, storage temperatures, expiration protocols, and specialized cellular modifications directly ensures product potency and patient survival.

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1. Blood Component Preparation by Differential Centrifugation

Fractionation of whole blood into red blood cells, platelets, and plasma derivatives relies on the physical principle of differential centrifugation—exploiting distinct cellular densities ($RBCs > WBCs > Platelets > Plasma$) under calibrated centrifugal fields:

                         ┌──────────────────────────────────────────────┐
                         │         Freshly Collected Whole Blood        │
                         │             (Within 8 Hours)                 │
                         └──────────────────────┬───────────────────────┘
                                                │
                                                │ Light Spin Centrifugation
                                                │ (Low speed, short duration)
                                                ▼
                         ┌──────────────────────────────────────────────┐
                         │           Primary Separation Layer           │
                         ├──────────────────────┬───────────────────────┤
                         │   Bottom Layer:      │   Supernatant Layer:  │
                         │   Packed Red Cells   │   Platelet-Rich       │
                         │   (PRBCs)            │   Plasma (PRP)        │
                         └──────────┬───────────┴───────────┬───────────┘
                                    │                       │
        Add Additive Solution       │                       │ Heavy Spin Centrifugation
        (AS-1, AS-3, AS-5)          │                       │ (High speed, long duration)
        Store at 1-6°C (42 Days)    │                       ▼
                                    │           ┌───────────────────────┐
                                    │           │ Supernatant:          │
                                    │           │ Platelet-Poor Plasma  │
                                    │           │ (Freeze within 8 hrs) │
                                    │           └───────────┬───────────┘
                                    │                       │ Freeze at ≤-18°C
                                    │                       ▼
                                    │           ┌───────────────────────┐
                                    │           │ Fresh Frozen Plasma   │
                                    │           │ (FFP, 1-year shelf)   │
                                    │           └───────────┬───────────┘
                                    │                       │ Thaw at 1-6°C
                                    │                       │ Cold precipitate
                                    │                       ▼
                                    │           ┌───────────────────────┐
                                    │           │ Cryoprecipitate (AHF) │
                                    │           │ Refreeze at ≤-18°C    │
                                    │           └───────────────────────┘
                                    │
                                    ▼
                         ┌──────────────────────────────────────────────┐
                         │ Pellet: Platelet Concentrate                 │
                         │ Resuspend in 40-70 mL plasma                 │
                         │ Store at 20-24°C with agitation (5 Days)     │
                         └──────────────────────────────────────────────┘

Centrifugation Phases

1. The Light Spin:
   • Parameters: Low centrifugal acceleration and short duration (e.g., $\approx 2,000 \times g$ for $3\text{ to }4\text{ minutes}$ at $20\text{--}24^\circ\text{C}$).
   • Result: Dense red blood cells settle into a packed lower fraction, while platelets remain suspended in the supernatant plasma, yielding Platelet-Rich Plasma (PRP).
   • The PRP is expressed into an attached satellite transfer pack using a manual or automated plasma extractor, leaving the packed red blood cells behind.
2. The Heavy Spin (Hard Spin):
   • Parameters: High centrifugal acceleration and extended duration (e.g., $\approx 5,000 \times g$ for $5\text{ to }7\text{ minutes}$ at $20\text{--}24^\circ\text{C}$).
   • Result: When applied to the PRP, platelets pellet densely at the bottom of the satellite pack. The clear supernatant, termed Platelet-Poor Plasma (PPP), is expressed into a third satellite bag.
   • Platelet Rest Period: The tightly pelleted platelets must sit undisturbed at room temperature for $60\text{ to }90\text{ minutes}$ to allow disaggregation before gentle resuspension in $40\text{ to }70\text{ mL}$ of residual plasma.
   • A heavy spin applied directly to freshly collected whole blood can also be utilized when platelets are not being harvested, rapidly separating Packed Red Blood Cells from cell-free plasma.

Closed System vs. Open System Expiration Limits

• Closed System: When components are prepared using integrated satellite packs interconnected by sterile factory tubing, the hermetic integrity of the system is maintained. Components retain their full regulatory shelf lives.
• Open System Breach: If an aseptic seal is broken—such as spiking a port, pooling units without an approved sterile connecting device (SCD), or performing manual saline washing—the component is subject to strict shortened expiration limits due to potential airborne bacterial inoculation:
  • Storage at $1\text{ to }6^\circ\text{C}$: Expiration is strictly $24\text{ hours}$ from the moment of breach.
  • Storage at Room Temperature ($20\text{ to }24^\circ\text{C}$): Expiration is strictly $4\text{ hours}$ from the moment of breach.

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2. Packed Red Blood Cells (PRBCs)

Packed Red Blood Cells are indicated to increase oxygen-carrying capacity in patients with symptomatic anemia, acute surgical or traumatic hemorrhage, or bone marrow failure.

• Storage and Transport Temperatures:
  • Storage: Maintained strictly at $1\text{ to }6^\circ\text{C}$ in monitored blood bank refrigerators equipped with continuous temperature recorders and audible alarms.
  • Transport: Maintained at $1\text{ to }10^\circ\text{C}$ during inter-facility transit in validated insulated containers containing wet ice (which floats above components, never in direct freezing contact).
• Shelf Life by Preservative Formulation:
  • CPD / CP2D: 21 days.
  • CPDA-1: 35 days.
  • Additive Solutions (AS-1, AS-3, AS-5): 42 days.
• Hematocrit and Quality Control Standards:
  • CPDA-1 units must maintain a hematocrit of $\le 80\%$ (typically $70\%\text{--}80\%$); higher hematocrit impedes infusion flow rates and deprives cells of sufficient nutrient plasma.
  • Additive solution units maintain a lower hematocrit of $55\%\text{ to }65\%$, providing superior viscosity and rapid infusion kinetics.
• Expected Adult Clinical Increment:
  • In a standard $70\text{ kg}$, non-bleeding adult recipient, transfusion of one unit of PRBCs raises the circulating hemoglobin concentration by approximately $1.0\text{ g/dL}$ ($10\text{ g/L}$) and the hematocrit by approximately $3\%$ ($0.03$), evaluated at 24 hours post-transfusion.

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3. Platelet Concentrates: Whole Blood-Derived vs. Single-Donor Apheresis

Platelets are indicated for the treatment or prophylaxis of severe bleeding in thrombocytopenia (due to chemotherapy, aplastic anemia, or marrow infiltration) and qualitative platelet functional defects.

┌──────────────────────────────────────────────┬──────────────────────────────────────────────┐
│ Whole Blood-Derived Platelet Concentrate    │ Single-Donor Apheresis Platelet Unit         │
├──────────────────────────────────────────────┼──────────────────────────────────────────────┤
│ • Harvested from 1 unit whole blood          │ • Collected via automated apheresis machine  │
│ • Minimum Yield: ≥5.5 x 10^10 platelets      │ • Minimum Yield: ≥3.0 x 10^11 platelets      │
│ • Suspension Volume: 40-70 mL plasma         │ • Suspension Volume: 200-300 mL plasma       │
│ • Standard dose requires pooling 4-6 units   │ • Equal to 6 pooled random donor units       │
│ • Exposes recipient to multiple donors       │ • Minimizes donor exposure, reduces HLA risk │
│ • Pooled open system expires in 4 hours      │ • Closed system expires in 5 days            │
└──────────────────────────────────────────────┴──────────────────────────────────────────────┘

• Storage Temperature and Agitation Protocols:
  • Stored strictly at $20\text{ to }24^\circ\text{C}$ (room temperature) with continuous gentle horizontal agitation on dedicated flatbed agitators or rotating drums.
  • Pathophysiological Basis for Agitation: Constant motion prevents platelet clumping and facilitates continuous gas exchange across the plastic container membrane. Influx of oxygen ($O_2$) and efflux of carbon dioxide ($CO_2$) prevents anaerobic accumulation of lactic acid, maintaining product $\text{pH} \ge 6.2$ across the storage interval.
  • The Bacterial Proliferation Dilemma: Because platelets must be stored at ambient room temperature ($20\text{--}24^\circ\text{C}$), they carry an exceptionally high risk of supporting rapid bacterial proliferation from skin flora or transient donor bacteremia. Consequently, shelf life is strictly capped at $5\text{ days}$ (or 7 days with approved bacterial screening devices).
• Clinical Increment:
  • One single-donor apheresis unit (or an equivalent pool of 4 to 6 whole blood-derived units) raises the adult platelet count by $30,000\text{ to }50,000/\mu\text{L}$ ($30\text{ to }50 \times 10^9/\text{L}$) measured 1 hour post-transfusion in a non-bleeding, non-refractory recipient.

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4. Plasma Derivatives: Fresh Frozen Plasma, Thawed Plasma, and Cryoprecipitate

Fresh Frozen Plasma (FFP)

• Preparation and Freezing: Plasma separated from whole blood and frozen to $\le -18^\circ\text{C}$ within 8 hours of phlebotomy (or $\le -20^\circ\text{C}$ in European standards).
• Shelf Life:
  • 1 year when stored at $\le -18^\circ\text{C}$.
  • 7 years when stored at ultra-low temperatures of $\le -65^\circ\text{C}$.
• Coagulation Factor Content: Contains normal plasma concentrations of all soluble clotting factors, including normal physiological levels of the heat-labile coagulation factors—Factor V and Factor VIII.
• Thawing Protocol: Thawed at $30\text{ to }37^\circ\text{C}$ in a temperature-controlled, circulating water bath using a protective waterproof plastic overwrap (to prevent port contamination) or an approved dry microwave heating system. Once thawed, FFP is stored at $1\text{ to }6^\circ\text{C}$ and expires in $24\text{ hours}$.
• Thawed Plasma (Extended Storage):
  • If thawed FFP is not infused within 24 hours, it may be relabeled as Thawed Plasma and retained at $1\text{ to }6^\circ\text{C}$ for up to 4 additional days (total 5 days from initial thaw).
  • Factor Activity Profile: Labile Factors V and VIII decline significantly (Factor VIII drops by $50\%$ within 48 hours), but stable factors (Factor II, VII, IX, X, and fibrinogen) remain therapeutically robust. Thawed plasma is indicated for urgent warfarin reversal, massive transfusion resuscitation, and plasma exchange in Thrombotic Thrombocytopenic Purpura (TTP).

Cryoprecipitated Antihemophilic Factor (Cryoprecipitate / AHF)

• Preparation Mechanics: FFP stored at $\le -18^\circ\text{C}$ is allowed to thaw slowly at $1\text{ to }6^\circ\text{C}$ overnight. As the plasma liquefies, a cold-insoluble white precipitate remains. The unit is subjected to a heavy spin at $1\text{ to }6^\circ\text{C}$, the supernatant cryo-depleted plasma is expressed leaving the precipitate in $10\text{ to }15\text{ mL}$ of plasma, and the container is refrozen at $\le -18^\circ\text{C}$ within 1 hour.
• Shelf Life: 1 year stored at $\le -18^\circ\text{C}$.
• Mandatory Component Yield Standards:
  • Factor VIII:C: $\ge 80\text{ International Units (IU)}$ per unit.
  • Fibrinogen: $\ge 150\text{ mg}$ of clottable fibrinogen per unit (typically $200\text{--}250\text{ mg}$).
  • Also rich in von Willebrand factor (vWF) ($40\%\text{--}70\%$ of original plasma), Factor XIII ($20\%\text{--}30\%$), and Fibronectin.
• Thawing, Storage, and Infusion Handling:
  • Thawed at $30\text{ to }37^\circ\text{C}$ in a water bath.
  • CRITICAL STORAGE RULE: Once thawed, Cryoprecipitate must be kept at $20\text{ to }24^\circ\text{C}$ (ROOM TEMPERATURE)! It must NEVER be refrigerated at $1\text{ to }6^\circ\text{C}$, because hypothermic temperatures cause fibrinogen and von Willebrand factor polymers to spontaneously reprecipitate, rendering the component unusable.
  • Expiration Post-Thaw: Single unpooled units expire in $6\text{ hours}$ at $20\text{--}24^\circ\text{C}$. If pooled in an open system, the pooled component expires in $4\text{ hours}$.
• Clinical Indications: Hypofibrinogenemia ($<100\text{ mg/dL}$), acute Disseminated Intravascular Coagulation (DIC) with fibrinogen consumption, obstetrical hemorrhage (placental abruption, amniotic fluid embolism), dysfibrinogenemia, and Factor XIII deficiency.

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5. Specialized Component Modifications

┌────────────────────────────────────────────────────────────────────────────────────────┐
│                     Specialized Cellular Component Modifications                       │
├─────────────────────────┬────────────────────────────┬─────────────────────────────────┤
│ Leukoreduction          │ Gamma Irradiation          │ Saline Washing                  │
├─────────────────────────┼────────────────────────────┼─────────────────────────────────┤
│ • Goal: <5 x 10^6 WBCs  │ • Dose: 25 Gy center       │ • Removes >99% plasma proteins  │
│ • Prevents FNHTR        │ • Inactivates T-cells      │ • Indicated for anti-IgA /      │
│ • Prevents CMV spread   │ • Prevents fatal TA-GVHD   │   severe recurrent anaphylaxis  │
│ • Halts HLA-alloimmune  │ • Mandatory: blood kin,    │ • Expires in 24 hrs at 1-6°C    │
│   refractoriness        │   immunocompromised        │ • Eliminates extracellular K+   │
│ • Retains shelf life    │ • Limits PRBCs to 28 days  │   and microaggregates           │
└─────────────────────────┴────────────────────────────┴─────────────────────────────────┘

Leukoreduction

• Mechanism: High-efficiency mechanical depth filtration using polyester or polyurethane micro-fibers, applied pre-storage within 48 hours of phlebotomy.
• Regulatory Standard: Final component must contain $<5.0 \times 10^6$ residual white blood cells per unit while retaining $\ge 85\%$ of original red blood cells.
• Clinical Indications and Benefits:
  1. Prevents Febrile Non-Hemolytic Transfusion Reactions (FNHTR) caused by recipient antileukocyte antibodies or cytokines (IL-1, IL-6, TNF-$\alpha$) released by aging granulocytes.
  2. Prevents transfusion transmission of Cytomegalovirus (CMV) and Human T-Cell Lymphotropic Virus (HTLV-I/II), because these viruses reside intracellularly within donor leukocytes ("CMV-safe blood").
  3. Decreases recipient HLA class I alloimmunization, reducing the incidence of immune-mediated platelet refractoriness in multi-transfused oncology patients.

Gamma Irradiation

• Mechanism: Exposure of cellular products (PRBCs, Platelets, Granulocytes) to a gamma radiation source (Cesium-137 or Cobalt-60) or specialized X-ray irradiators. The central dose delivered to the container must be at least $25\text{ Gy}$ ($2,500\text{ cGy}$), with no part of the bag receiving less than $15\text{ Gy}$.
• Biological Target: Crosslinks DNA in viable donor T-lymphocytes, completely abolishing their proliferative and mitotic capabilities without damaging non-nucleated red cells or platelets.
• Absolute Prevention of TA-GVHD: Transfusion-Associated Graft-versus-Host Disease (TA-GVHD) occurs when donor T-lymphocytes engraft in a recipient whose immune system cannot reject them. The engrafted donor T-cells mount a lethal immune assault against host tissues (bone marrow, GI tract, liver, skin), leading to profound pancytopenia with a mortality rate exceeding $90\%$.
• Mandatory Indications for Irradiation:
  1. Directed donations from biological first-degree relatives (parents, siblings, children): Even in immunocompetent recipients, shared HLA haplotypes prevent the recipient's immune cells from recognizing the donor cells as foreign, enabling fatal donor lymphocyte engraftment.
  2. HLA-matched or crossmatched platelet transfusions.
  3. Severe immunocompromised recipients: Congenital cellular immunodeficiencies (SCID, DiGeorge syndrome), allogeneic or autologous hematopoietic stem cell transplant recipients, hematologic malignancies undergoing intensive therapy with purine analogs (fludarabine, cladribine).
  4. Intrauterine transfusions and exchange transfusions in premature neonates.
• Shelf Life Restriction: Gamma irradiation damages red cell membranes, accelerating potassium efflux during storage. Consequently, the shelf life of irradiated PRBCs is restricted to $28\text{ days}$ from the date of irradiation, or the original expiration date, whichever is shorter.

Saline Washing

• Mechanism: Cellular components (PRBCs or platelets) are washed with $1\text{ to }2\text{ liters}$ of sterile normal saline ($0.9\%\text{ NaCl}$) using automated centrifugation cell washers, removing $>99\%$ of extracellular plasma proteins, microaggregates, and extracellular potassium.
• Clinical Indications:
  1. IgA-deficient patients with confirmed anti-IgA antibodies: Even minute traces ($<10\ \mu\text{g}$) of donor plasma IgA trigger catastrophic IgE/IgG-mediated anaphylactic shock.
  2. Patients with severe, recurrent, life-threatening allergic or anaphylactic reactions unresponsive to pre-medication.
  3. Neonatal hyperkalemic risk during rapid prime-volume cardiac bypass surgery.
• Expiration Constraint: Because saline washing involves entering the unit via an open washing system, washed PRBCs must be stored at $1\text{ to }6^\circ\text{C}$ and expire strictly within $24\text{ hours}$.

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6. Comprehensive Blood Component Comparison Matrix

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7. Storage Equipment, Transport, Inspection, and Issue

Storage and Transport Temperatures

Storage Equipment

• Blood bank refrigerators, freezers, and platelet incubators are used only for blood, components, and reagents. They have continuous temperature monitoring and audible alarms set to sound before components go out of range.
• Where recording is not automatic, temperatures are recorded at regular intervals (commonly every 4 hours), and alarm checks are documented. A power-failure plan states where components go if equipment fails.
• Platelet agitators keep platelets suspended and allow gas exchange; a stopped agitator for an extended period harms platelet function.

Transport Containers

• Validated insulated containers with wet ice (separated from direct contact with red cell bags) or refrigerant packs keep red cells at 1 to 10 °C. Each shipment carries a temperature indicator or a validated maximum transit time, and the receiving facility checks the temperature on arrival.

Visual Inspection Before Issue

Every unit is inspected before release. Do not issue a unit with:

• Hemolysis (pink or red plasma or a red line at the red cell-plasma interface), or clots.
• Abnormal color, such as purple or dark red cells or brown, green, or very cloudy plasma, which can signal bacterial contamination.
• Leaks, broken seals, or illegible or mismatched labels.

Issue and Return

• At issue, the technologist and the person receiving the unit check the recipient's identification and the unit number, ABO/Rh, expiration date, and compatibility record together, and both sign the issue record.
• Units returned unused can be reissued only if the seals are intact and the facility's validated time and temperature limits were met. The traditional "30-minute rule" for red cells has largely been replaced by limits validated with temperature indicators or validated containers.