Describe Blood Component Therapy in detail.

The Principle of Component Therapy

Component therapy separates one donation into its parts so the patient receives only the component they need. This is standard for two reasons: one donation then treats several patients, and each patient avoids the antigens and volume of the components they do not require. The guiding rule is to ask what the patient is short of and replace exactly that.

Components, Content & Dosing

Thresholds illustrate the reasoning: red cells at Hb below ~7 g/dL (~8 in cardiac disease); platelets below 10×10⁹/L prophylactically, below 50 before surgery; cryoprecipitate when fibrinogen falls below ~1 g/L.

Grouping & Cross-matching

Every transfusion must be ABO and Rh compatible. Group O negative is the universal red-cell donor (used in emergencies) and AB positive the universal recipient; the serum is cross-matched against donor cells beforehand. The deadliest reaction is an acute haemolytic reaction from a clerical error (wrong unit to wrong patient), so bedside identity checks are mandatory and the patient is observed closely in the first 15 minutes.

Modified Products & Storage

Components can be tailored: leucodepleted (reduces febrile reactions/CMV), irradiated (prevents transfusion-associated graft-versus-host disease in the immunocompromised), and washed (for severe allergy). Each has its own storage need that sets shelf life — red cells 2–6 °C, platelets room temperature with agitation (~5–7 days), FFP/cryoprecipitate frozen. Whole blood is now rarely used.

Transfusion Reactions — an Overview

Every prescriber must know the reactions components can provoke. The most feared is the acute haemolytic reaction from ABO incompatibility — almost always a clerical error — causing fever, loin pain, haemoglobinuria, DIC and renal failure, and demanding that the transfusion be stopped immediately. Others include the common but benign febrile non-haemolytic reaction, allergic/anaphylactic reactions, TACO (circulatory overload → pulmonary oedema) and TRALI (transfusion-related acute lung injury), plus delayed haemolysis and infection.

The Storage Lesion & Autologous Transfusion

During storage, red cells progressively leak potassium, lose 2,3-DPG, and become acidic and cold — the 'storage lesion' that underlies the hyperkalaemia, hypothermia and acidosis of large transfusions. Where possible a patient may receive their own blood (predeposited or intra-operatively salvaged) — autologous transfusion — which eliminates incompatibility and infection risk, though it is unsuitable in cancer or infected fields.

Emergency Release of Blood

When there is no time for full cross-matching, blood is issued in escalating order of safety as time allows: immediate emergency group O (O-negative for women of childbearing age) → type-specific ABO/Rh-matched blood (a few minutes) → fully cross-matched blood (~45 minutes). Rh-negative status is protected in girls and women of childbearing age to prevent future haemolytic disease of the newborn. Safe transfusion is a process — correct sample labelling, group-and-save, a final two-person bedside identity check, and close observation, especially in the first 15 minutes when severe reactions declare themselves.

Component therapy treats the specific deficit and conserves supply.

• One donation → several patients; give only the needed component.
• Packed cells (anaemia, +1 g/dL/unit), FFP (all factors, ~15 mL/kg), platelets (thrombocytopenia+bleeding), cryoprecipitate (fibrinogen).
• Thresholds: Hb <7 (<8 cardiac); platelets <10 prophylaxis, <50 pre-surgery; cryo if fibrinogen <1 g/L.
• ABO/Rh compatible + cross-match; O-negative universal donor, AB-positive universal recipient; clerical error is the deadliest risk.
• Modified: leucodepleted/irradiated/washed; storage — red cells 2–6 °C, platelets room temp with agitation, FFP/cryo frozen.