Blood component therapy is the practice of separating whole blood donations into individual components — red blood cells, platelets, plasma, and cryoprecipitate — so that patients receive only the specific component they need. This maximizes the utility of each donation and minimizes unnecessary transfusion risks. Component therapy requires understanding of each product’s indications, storage, dosing, and potential adverse effects.
Red Blood Cell (RBC) Concentrates
Each unit of packed RBCs is prepared from one whole blood donation (450 mL) by centrifugation and removal of plasma, with addition of an additive solution (SAG-M: saline, adenine, glucose, mannitol) to maintain viability during storage. A typical unit has a hematocrit of 55–65% and volume of 250–350 mL, raising hemoglobin by approximately 1 g/dL (hematocrit by 3%) in an average adult. RBCs are stored at 1–6°C: CPDA-1 preserves for 35 days, additive solutions extend to 42 days. Storage lesions include decreased 2,3-DPG (reverses within 24 hours of transfusion), potassium leakage (hyperkalemia risk in massive transfusion), and microvesicle formation. Indications for RBC transfusion include symptomatic anemia (hemoglobin < 7–8 g/dL), acute blood loss with hemodynamic instability, and specific thresholds in critical care (restrictive strategy: 7 g/dL, liberal: 9–10 g/dL in acute coronary syndrome). Each unit is tested for ABO and Rh, and crossmatched to the intended recipient. Compatible RBC units are ABO-identical, but group O units are universal donor.
Platelet Concentrates
Platelet concentrates are prepared either by pooling platelets from 4–6 whole blood donations (random donor platelets, RDP) or by single-donor apheresis (SDP). One unit of apheresis platelets (approximately 3–6 × 10¹¹ platelets in 200–400 mL plasma) is equivalent to a pool of RDPs. Platelets are stored at 20–24°C with continuous agitation for up to 5–7 days, depending on storage system. Bacterial contamination is the primary infectious risk (platelets are stored at room temperature), requiring bacterial screening or pathogen reduction technology. The corrected count increment (CCI) at 1 hour and 18–24 hours post-transfusion assesses transfusion effectiveness. Indications include prophylactic transfusion for severe thrombocytopenia (< 10 × 10⁹/L in stable patients, < 20 × 10⁹/L with fever or sepsis, < 50 × 10⁹/L for invasive procedures) and therapeutic transfusion for active bleeding with thrombocytopenia or platelet dysfunction.
Fresh Frozen Plasma (FFP) and Other Plasma Products
FFP is prepared from whole blood or apheresis and frozen to -18°C within 8 hours of collection, preserving all coagulation factors (including labile factors V and VIII). It contains approximately 1 IU/mL of each factor. Thawed FFP must be used within 24 hours (or stored at 1–6°C for up to 5 days as thawed plasma). Indications include multiple coagulation factor deficiencies (DIC, liver disease, massive transfusion, warfarin reversal when prothrombin complex concentrate is unavailable), therapeutic plasma exchange for TTP, and deficiency of specific factors when concentrates are unavailable. FFP is not indicated for volume expansion or as a nutritional source. A typical dose is 10–20 mL/kg.
Cryoprecipitate
Cryoprecipitate is prepared by thawing FFP at 1–6°C and collecting the cold-insoluble precipitate. It is rich in factor VIII (80–150 IU/unit), von Willebrand factor, fibrinogen (150–350 mg/unit), factor XIII, and fibronectin. A pool of 5–10 donor units constitutes one therapeutic dose. The primary indication is hypofibrinogenemia (< 100–150 mg/dL) in bleeding patients (DIC, massive transfusion, trauma). It is also used for von Willebrand disease when vWF-containing concentrates are unavailable, and for factor XIII deficiency. Cryoprecipitate is not virally inactivated, so pathogen-reduced alternatives (fibrinogen concentrate, factor concentrates) are preferred when available.
Special Products
Irradiated blood products are treated with 25–30 Gy gamma radiation to inactivate donor T-lymphocytes and prevent transfusion-associated graft-versus-host disease (TA-GVHD). Indications include intrauterine transfusion, congenital immunodeficiency, hematopoietic stem cell transplant, Hodgkin lymphoma, and donations from blood relatives. Leukoreduced products (< 5 × 10⁶ leukocytes/unit) reduce febrile non-hemolytic transfusion reactions, CMV transmission, and platelet alloimmunization. Washed blood products remove plasma proteins (for severe allergic reactions, IgA deficiency). Pathogen-reduced products (using amotosalen-UVA or riboflavin-UV) inactivate a broad range of pathogens.
Massive Transfusion
Massive transfusion is defined as replacement of > 1 blood volume in 24 hours (> 10 units RBCs) or > 4 units RBCs in 1 hour. Massive transfusion protocols (MTP) deliver balanced ratios of RBCs:plasma:platelets (typically 1:1:1) to prevent dilutional coagulopathy. Laboratory monitoring during MTP includes serial PT/INR, aPTT, fibrinogen, platelet count, ionized calcium (citrate chelation causing hypocalcemia), potassium, and blood gas analysis. Goal-directed therapy with viscoelastic testing (TEG, ROTEM) is increasingly used to guide component selection.
