Transfusion

Why platelets must be stored in room temperature?

1. Cold storage can activate platelets: Cold storage of platelets at temperatures below room temperature (15 °C) can induce platelet activation, resulting in changes in platelet shape and functionality. This activation can lead to platelet aggregation and a decrease in platelet viability, making the stored platelets less effective for transfusion purposes.
2. Platelet clearance from circulation: Platelets stored at refrigerating temperatures are rapidly cleared from the bloodstream when transfused, reducing their effectiveness. Cold storage can cause clustering of glycoprotein Ib (GPIb) receptors on the platelet surface, which exposes beta-N-acetylglucosamine residues. These exposed residues are recognized by liver macrophages, leading to rapid clearance of the platelets through phagocytosis. This clearance mechanism limits the viability and availability of cold-stored platelets

---

Transfusion Products

Packed Red Blood Cells (pRBCs)

• Contents & Effect: Each unit contains ~250 mL of RBCs and increases Hemoglobin (Hb) by ~1 g/dL and Hematocrit (Hct) by ~3%. Its purpose is to increase oxygen-carrying capacity.
• Indications:
  • Restrictive Strategy (preferred): Symptomatic anemia or Hb <7-8 g/dL in hemodynamically stable, hospitalized patients.
  • Liberal Strategy: Higher threshold (e.g., Hb <10 g/dL) may be considered in acute coronary syndrome, severe sepsis, or active bleeding.
  • Acute hemorrhage or trauma with significant blood loss.
• Key Associations: One unit of pRBCs contains about 200-250 mg of iron, which can lead to iron overload in chronically transfused patients.

Platelets (PLTs)

• Contents & Effect: A single apheresis unit increases platelet count by ~30,000-50,000/µL. The main goal is to prevent or treat bleeding due to thrombocytopenia or platelet dysfunction.
• Indications:
  • Prophylactic: Platelet count <10,000-20,000/µL to prevent spontaneous bleeding, especially with fever or sepsis.
  • Therapeutic (Active Bleeding):
    • <50,000/µL for major surgery or significant hemorrhage.
    • <100,000/µL for CNS or ocular bleeding/surgery.
• Contraindications: Generally contraindicated in Thrombotic Thrombocytopenic Purpura (TTP) and Heparin-Induced Thrombocytopenia (HIT) unless life-threatening hemorrhage is present.

Fresh Frozen Plasma (FFP)

• Contents & Effect: Contains all coagulation factors, including fibrinogen and ADAMTS13. Primarily used to correct coagulopathy.
• Indications:
  • Active bleeding with multiple factor deficiencies (e.g., PT/PTT >1.5x normal), such as in massive transfusion protocols, DIC, or liver disease.
  • Urgent reversal of warfarin when prothrombin complex concentrates (PCC) are unavailable.
  • Plasma exchange for TTP.
• DDx/Contraindications: Not to be used as a simple volume expander or for correcting coagulopathy without active bleeding. More specific treatments like Vitamin K or factor concentrates should be used when appropriate.

Cryoprecipitate (“Cryo”)

• Contents & Effect: A concentrated product derived from FFP. Rich in fibrinogen, Factor VIII, Factor XIII, von Willebrand factor (vWF), and fibronectin.
• Indications:
  • Hypofibrinogenemia (<100-150 mg/dL), especially in the setting of massive hemorrhage or DIC.
  • Second-line therapy for Hemophilia A and von Willebrand disease if specific factor concentrates are not available.
  • Bleeding associated with uremia.
• Key Associations: One unit of FFP contains the equivalent of about two units of cryoprecipitate but at a much higher volume. A standard adult dose is a pool of 10 units of cryoprecipitate.

Special Product Modifications

• Leukoreduction (Filtration):
  • Mechanism: Removes WBCs via filtration.
  • Purpose: Reduces the risk of Febrile Non-Hemolytic Transfusion Reactions (FNHTR) (most common adverse reaction), CMV transmission (as CMV resides in leukocytes), and HLA alloimmunization.
  • Removes >99.9% of the white blood cells, but residual lymphocytes are still sufficient to cause Graft-versus-Host Disease.
• Irradiation:
  • Mechanism: Inactivates donor T-lymphocytes using gamma or X-ray radiation to prevent them from replicating.
  • Purpose: Prevents Transfusion-Associated Graft-versus-Host Disease (TA-GVHD), a rare but often fatal complication.
  • Indications: Severely immunocompromised patients (e.g., bone marrow transplant recipients, patients with congenital immunodeficiencies like DiGeorge syndrome), and when receiving blood from a relative.
• Washed RBCs:
  • Mechanism: Removes plasma proteins from the pRBC unit.
  • Purpose: Prevents severe allergic reactions, particularly in patients with a history of anaphylaxis or known IgA deficiency.