Transfusion Therapy and Blood Products

Blood Transfusion and Coagulation Management

• Goals of transfusion therapy:
  • Increase oxygen-carrying capacity and intravascular volume
  • Minimize the use of blood and blood products
• Normal hemostatic mechanisms:
  • von Willebrand factor (vWF)
  • Tissue factor (TF)
  • Antithrombin (AT)
  • Activated protein C (APC)
  • Tissue factor pathway inhibitor (TFPI)
  • Tissue plasminogen activator (tPA)

Indications for Transfusion

• 1988 NIH consensus:
  • Healthy patients with Hb >10 g/dL rarely require perioperative blood transfusions
  • Patients with acute anemia < 7 g/dL frequently require blood transfusions
• Determining the need for transfusion:
  • Clinical judgment based on cardiovascular status, age, anticipated additional blood loss, arterial oxygenation, SVO2, CO, and intravascular blood volume
  • Liberal vs. restrictive blood transfusion strategy based on Hgb value
• Separation of whole blood for component therapy:
  • PRBC (Packed Red Blood Cells)
  • Platelet concentrates
  • Fresh Frozen Plasma (FFP)
  • Cryoprecipitate

Blood Products

• PRBC:
  • Hct 50%-70%
  • Compatible with D50.4%NS, D5NS, 0.9% NS, and Normosol-R
  • pH 7.4
  • Recommendations for transfusion:
    • Blood loss > 20% of blood volume
    • Hgb level < 8 g/dL
    • Hgb level < 9 to 10 g/dL with major disease
    • Hgb level < 10 g/dL with autologous blood
    • Hgb level < 11 to 12 g/dL if ventilator-dependent
• Platelet concentrates:
  • Pooled concentrates from 4 to 6 whole-blood donations or as apheresis concentrates
  • 1U Plt concentrate increases platelet count by 7,000 to 10,000/mm³ at 1 hour after transfusion
  • Indications for transfusion:
    • Rarely prophylactically for ITP
    • Preop for surgical and OB patients if plts < 50 × 10⁹/L
    • Microvascular bleeding or known plt dysfunction
• Fresh Frozen Plasma (FFP):
  • Contains all plasma proteins, including factors V and VIII
  • Compatible with recipients' ABO types, Rh not needed
  • Usual dose is 5 to 8 mL/kg, up to 10 to 30 mL/kg
  • ASA guidelines for administration:
    • Replacement of inherited single coagulation factor deficiencies
    • Replacement of multiple coagulation factor deficiencies with associated bleeding
    • As a component of plasma exchange in patients with ITP
    • Reversal of warfarin anticoagulation
    • Prevention of dilutional coagulopathy
• Cryoprecipitate:
  • Contains concentrated factors VIII:C, VIII:vWF, fibrinogen, factor XIII, and fibronectin
  • Give as rapid infusion via filter within 6 hours of thawing
  • Indications for use:
    • Bleeding due to acquired hypofibrinogenemia

Transfusion Reactions and Risks

• Transfusion-Related Acute Lung Injury (TRALI):
  • Leading cause of transfusion-related mortality
  • Manifested as non-cardiogenic pulmonary edema
  • Symptoms: fever, dyspnea, fluid in the endotracheal tube, and severe hypoxia
  • Risk factors: higher interleukin-8 (IL-8) levels, liver surgery, ETOH abuse, shock, higher peak airway pressures, smoking, and positive fluid-balance
  • Tx: stop transfusion, ICU support
• Nonhemolytic reactions:
  • Febrile reactions
  • Allergic reactions
  • Anaphylactoid and anaphylactic reactions
• Other risks of blood transfusions:
  • Infectious risks: HIV, Hep B, Hep C, Cytomegalovirus, bacteria
  • Non-infectious risks: transfusion-associated circulatory overload, hypotension, graft-versus-host, transfusion-related immunomodulation, and transfusion-related AKI

Evaluation and Management of Perioperative Coagulopathy

• Prevention and management of surgical bleeding:
  • Algorithms and use of TEG
  • Patient factors: insult from cardiopulmonary bypass, fibrinolysis, platelet dysfunction, clotting factors, and hypothermia
• Useful drugs to reduce bleeding during cardiac surgery:
  • Protamine
  • Tranexamic acid or epsilon aminocaproic acid
  • Recombinant factor VIIa (aprotinin)
  • Desmopressin
• Protamine and reversal of anticoagulation:
  • Protamine binds heparin and inactivates it
  • 1 mg protamine neutralizes 100 units of heparin
  • Usual protocols: protamine dose based on the total amount of heparin given for the procedure
  • Contraindications and side effects: severe hypotension, anaphylactoid reaction, decreased SVR, RV failure
• Antifibrinolytics:
  • Tranexamic acid (TXA) for cardiac surgery:
    • Routinely used in cardiac surgery
    • More favorable profile compared to EACA
    • Administered loading dose of 1g before incision, followed by 1mg/kg/hr
    • Decreased blood loss, chest tube drainage, and blood transfusion
  • Tranexamic acid (TXA) for non-cardiac surgery:
    • Used for treatment and/or prevention of excessive blood loss
    • 1g before incision and 1g at the end of surgery
    • Decreased major bleeding and risk of death and hemorrhage
  • Desmopressin:
    • Analog of vasopressin
    • Releases coagulation system mediators from vascular endothelium
    • Dose: 0.3 µg/kg, IV, SC, and intranasal
    • Metabolism in liver and kidney, urinary excretion, plasma half-life of 2.5 to 4 hours
    • Rapid IV administration decreases BP and SVR
    • Specific hemostatic benefits include uremia, cirrhosis, aspirin therapy, and surgery of various types

This quiz assesses understanding of transfusion therapy, including its goals, decision-making factors, and blood products. It covers platelet concentrates, blood transfusions, and hemoglobin levels.