7.2 Transfusion Practice, Indications for Blood Components, and Administration

Transfusion Practice and Indications

Transfusion medicine requires precise clinical judgment. Blood components should only be prescribed when a specific deficit cannot be corrected by other means. Each blood product carries inherent risks, including transfusion reactions and volume overload, meaning therapy must be targeted and evidence-based. Understanding the exact indications and expected outcomes for each component is crucial for the MLS exam and clinical practice.

Packed Red Blood Cells (PRBCs)

PRBCs are the most frequently transfused blood product. They restore oxygen-carrying capacity in patients with anemia or acute blood loss.

• Indications: Symptomatic anemia (e.g., fatigue, tachycardia, shortness of breath), acute hemorrhage, and oncology patients undergoing chemotherapy. The traditional trigger for transfusion in stable, non-bleeding patients is a hemoglobin of <7.0 g/dL.
• Expected Outcome: In an average adult, one unit of PRBCs should increase the hemoglobin by 1 g/dL or the hematocrit by 3%.
• Contraindications: PRBCs should never be used purely for volume expansion, wound healing, or to improve general well-being. Pharmacological alternatives, such as iron or erythropoietin, should be used for nutritional anemias.
• Modifications:
  • Leukoreduced: Used to prevent febrile non-hemolytic transfusion reactions (FNHTR), HLA alloimmunization, and CMV transmission.
  • Irradiated: Prevents Transfusion-Associated Graft-vs-Host Disease (TA-GVHD) by cross-linking T-lymphocyte DNA, rendering them incapable of proliferating. Indicated for immunocompromised patients, directed donations from blood relatives, and intrauterine transfusions.
  • Washed: Removes plasma proteins to prevent severe allergic/anaphylactic reactions, particularly in IgA-deficient patients with anti-IgA antibodies.

Platelets

Platelet transfusions provide immediate hemostatic support for patients lacking functional or sufficient platelets.

• Indications: Prophylaxis in severe thrombocytopenia (platelets <10,000/µL), active bleeding with platelet counts <50,000/µL, or surgical patients requiring a threshold >50,000/µL. It is also used in patients with qualitative platelet disorders (e.g., Glanzmann thrombasthenia) despite normal counts.
• Expected Outcome: One unit of apheresis platelets (equivalent to 4-6 pooled random donor units) should increase the adult platelet count by 30,000 to 50,000/µL.
• Refractoriness: If the 10-minute to 1-hour post-transfusion increment is significantly lower than expected on two or more occasions, the patient may be refractory, often due to HLA or platelet-specific antibodies. HLA-matched platelets are required.

Fresh Frozen Plasma (FFP)

FFP is an unpurified mixture of all coagulation factors, rendering it highly versatile in managing coagulopathies.

• Indications: Management of bleeding patients with multiple coagulation factor deficiencies (e.g., liver disease, DIC), rapid warfarin reversal (when Prothrombin Complex Concentrate is unavailable), and massive transfusion protocols. It is also the replacement fluid of choice in Therapeutic Plasma Exchange for Thrombotic Thrombocytopenic Purpura (TTP).
• Expected Outcome: Usually dosed at 10-20 mL/kg, FFP will increase factor levels by approximately 20%, normalizing the PT/aPTT and achieving hemostasis.
• Contraindications: FFP should not be used for volume expansion or as a nutritional protein supplement.

Cryoprecipitate

Cryoprecipitate is a concentrated source of specific plasma proteins: Fibrinogen (Factor I), Factor VIII, Factor XIII, and von Willebrand Factor (vWF).

• Indications: The primary indication is hypofibrinogenemia (fibrinogen <100 mg/dL), such as in DIC or massive hemorrhage. It is also used for Factor XIII deficiency and as a secondary treatment for Hemophilia A or von Willebrand disease when recombinant concentrates are unavailable.
• Expected Outcome: A standard pool of 10 units will increase adult fibrinogen levels by approximately 50 mg/dL.

Administration and Monitoring

Safe administration of blood components is governed by rigid protocols to ensure the right unit reaches the right patient without complications.

• Patient Identification: The most critical step. The patient's wristband, blood unit label, and compatibility tag must be cross-checked by two healthcare professionals.
• Filters: All blood components must be transfused through a standard 170-260 micron filter to remove clots and debris.
• Time Limits: The transfusion must be initiated within 30 minutes of the unit leaving the blood bank. The transfusion must be completed within 4 hours to minimize the risk of bacterial proliferation at room temperature.
• Compatible Fluids: Normal saline (0.9% NaCl) is the ONLY fluid compatible with blood components. Ringer's lactate contains calcium, which overrides the citrate anticoagulant and causes clotting; Dextrose solutions cause red cell hemolysis.
• Monitoring: Vital signs must be recorded before starting, 15 minutes after initiation, and upon completion. The first 15 minutes are critical, as severe acute hemolytic reactions typically manifest with small volumes.

Therapeutic Phlebotomy

Therapeutic phlebotomy (therapeutic venesection) removes whole blood to reduce red-cell mass or iron load—not to collect a transfusion product for another patient.

Common indications:

• Polycythemia vera (and some secondary erythrocytoses): reduce hematocrit to target ranges set by the clinician (often <45% in PV).
• Hereditary hemochromatosis: remove iron via repeated phlebotomy until ferritin/transferrin saturation goals are met.
• Occasionally porphyria cutanea tarda when iron reduction is indicated.

Operational points tested on MLS exams:

• Use the same careful donor-style arm preparation and volume tracking, but the unit is typically discarded as biomedical waste unless a specific autologous protocol applies.
• Monitor the patient for vasovagal reactions; document pre-/post-vitals and volume removed.
• Distinguish therapeutic phlebotomy from autologous donation (blood kept for the same patients later surgery) and from routine allogeneic donation.