• A 36-year-old woman presents to the ED from a motor vehicle accident where she was hit by a drunk driver. She has several scrapes and discolorations on her right arm, leg, and flank, but no massive external bleeding. However, she appears obtunded. Her Glasgow Coma Scale score is 10. Her blood pressure is 85/50 mmHg, pulse is 100/min, and oxygen saturation of 94% on 2 L. After 2 liters of IV NS boluses, the patient's vital signs have not changed.
  • RBCs, platelets, and coagulation factors (fresh frozen plasma [FFP], cryoprecipitate, factor concentrate) can be transfused
  • Donated blood is separated into various components
    • whole blood is centrifuged into RBCs and platelet-rich plasma
    • platelet-rich plasma is further separated into platelets and plasma
    • FFP is plasma frozen within 8 hours (in the United States)
    • cryoprecipitate is FFP precipitate when thawed at low temperatures
    • platelets can be selectively removed while returning rest of blood to donor via apheresis
  • Blood products can be irradiated
    • prevents proliferation of donor T-cells in recipients
    • used for immunocompromised patients, first-degree relatives, HLA-matched products and intrauterine transfusions
  • Blood products can be leukodepleted via filtration to attain CMV-negativity
    • leukocytes contain CMV
    • used for potential transplant recipients, neonates, AIDS patients, seronegative pregnant women 
Packed Red Blood Cells (pRBCs)
  • Goal of pRBC transfusion is to increase oxygen carrying capacity
  • 1 unit of pRBC should increase Hb by 1 g/dL or Hct by 3-4%
  • Indications
    • Hb < 7 g/dL
      • may increase based on presence of symptoms
      • goal Hb between 7 and 10 g/dL during active bleeding
    • higher Hb threshold (Hb < 10 g/dL) for patients with
      • uncontrolled bleeding
      • cardiovascular disease (coronary artery disease, diabetes)
        • growing evidence that restrictive threshold of < 7 g/dL is okay
      • pulmonary disease (COPD)
    • dilution of sickled Hb in sickle cell disease patients
    • clinicical suspicion of blood loss - CBC will not demonstrate anemia in acute trauma 
  • "Type and Screen" (T&S) vs. "Type and Cross" (T&C)
    • T&S determines blood group, Rh status, presence of major/minor autoantibodies
    • T&C determines possible agglutination by mixing recipient and donor blood
  • pRBC options in order of preference
    • after T&S: crossmatched blood (not always available in emergencies)
    • after T&C: donor blood of same group / Rh as recipient
    • O negative blood for all females of reproductive age; O positive for all others
 Platelets (PLTs)
  • Goal of PLT transfusion is to decrease risk of bleeding
  • One unit of apheresis derived PLTs should increase PLT by ~50,000/uL
  • Indications
    • PLT < 10,000/uL for bleeding prophylaxis
      • threshold increases to < 20,000/uL in presence of comorbidities including coagulopathy (e.g., sepsis, DIC), fever, or active bleeding
    • higher levels needed for therapeutic purposes
      • < 50,000/uL for procedures a/w major blood loss, major surgery, or acute hemorrhage
      • < 100,000/uL for procedures involving CNS or eye
    • patients with platelet dysfunction (or on antiplatelet agents) and active hemorrhage need PLT transfusion within normal range
  • Relative contraindications
    • thrombotic thrombocytopenic purpura
    • heparin-induced thrombocytopenia
    • post-transfusion purpura
    • HELLP syndrome a/w preeclampsia
 Fresh Frozen Plasma (FFP)
  • Goal of FFP transfusion is to decrease risk of bleeding due to coagulation factor deficiency
  • Initial dosing at 10 mL/kg should raise factor levels by ~25%
    • PT and/or PTT are checked 15 to 30 minutes after transfusion to adjust dose as needed
  • Indications
    • PT/PTT > 1.5x midpoint of normal in patients with following conditions, particularly if surgery is indicated and cannot be postponed:
      • liver disease and active bleeding
      • use of vitamin K antagonists (e.g. warfarin)
      • sepsis, DIC, TTP/HUS
      • dilutionary coagulopathy from massive transfusion protocol
    • replacement of coagulatory factors in absence of specific concentrates
  • Goal of cryoprecipitate transfusion is to replace fibrinogen
  • Contains fibrinogen, vWF, fVIII, fXIII, and fibronectin
  • 1 unit of cryoprecipitate should increase fibrinogen level by 7-8 mg/dL
    • 1 unit of FFP has equivalent of 2 units of cryoprecipitate, but at cost of higher volume
  • Indications
    • fibrinogen < 80-100 mg/dL in massive hemorrhage
    • replacement of fVIII or vWF when fVIII concentrate or Humate (vWF/fVIII concentrate) is unavailable for fVIII deficiency and for von Willebrand disease
  • Most common adverse reactions to blood transfusion
    • febrile nonhemolytic transfusion reaction  
      • pathogenesis
        • secondary to generated and accumulated cytokines in stored blood components 
          • cytokines include
            • interleukin (IL)-1, -6, -8 and tumor necrosis factor (TNF)-α
          • leukocytes are the source of cytokines
      • clinical presentation
        • fever and chills 1-6 hours after transfusion
        • note this is a benign condition
      • management
        • stop the transfusion
        • antipyretics to control fever
        • evaluate for other causes of fever
      • prevention
        • pre-storage leukoreduction
    • transfusion related acute lung injury (TRALI)
      • presentation
        • shortness of breath roughly 30 minutes after transfusion 
      • pathophysiology
        • antibodies in donor blood against recipient leukocytes
      • evaluation
        • pulmonary edema seen on chest radiograph 
      • treatment
        • resolves spontaneously
  • Most serious adverse reactions to blood transfusion
    • acute hemolytic reaction 
      • e.g. due to ABO incompatibility
      • presents with fever/chills
      • classic triad of fever, back pain, and red/pink urine rarely seen
      • stop transfusion and obtain sample for direct Coombs test
    • dilutional pancytopenia
      • infusions of RBCs/fluids dilutes blood cells through plasma expansion and results in pancytopenia
    • bacterial contamination of blood
  • Other effects
    • citrate toxicity
      • citrate is an anticoagulant used in blood products
        • chelates calcium and magnesium
        • normally rapidly metabolized by liver
      • may cause hypocalcemia and hypomagnesemia leading to paresthesias
    • hyperkalemia
      • RBCs leak K+ during storage
    • coagulopathy
      • may require transfusion of FFP and platelets 

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