SM_255b: Blood Transfusions - Indications Flashcards
Describe indications for blood component transfusions
Indications for blood component transfusions
- RBCs: bleeding, anemia, perioperative blood management
- Platelets: thrombocytopenia, platelet dysfunction and hemostasis need
- Plasma: coagulopathy and bleeding / procedure
- Cryoprecipitate: low fibrinogen and bleeding / procedure
Describe whole-blood donation
Whole-blood donation
- 500 mL into citrate anticoagulant
- Separated at lab: RBCs plus plasma or platelets
Describe apheresis donation
Apheresis donation
- Blood drawn into continuous flow centrifuge: citrate anticoagulation
- Desired elements skimmed off
- Rest returned to donor
Describe normal blood volume
Normal blood volume
- Adult: 70 mL/kg
- Normal hematocrit: 40% RBCs
One RBC unit is ____ and includes ____ packed RBCs after centrifugation
One RBC unit is RBC content from a 500-mL whole blood collection that includes 300 mL packed RBCs after centrifugation
- 1 g/dL rise in Hb per unit
- Half life in blood: 30 days
Descriibe indications for RBC transfusion in acute bleeding
Indications for RBC transfusion in acute bleeding
- Intravascular blood volume is first priority: IV fluids, avoid hypovolemia and hypoperfusion
- Very early Hgb/Hct levels may not yet reflect blood loss, until intravascular volume expanded with fluid
- RBC transfusions usually needed when acute blood loss reaches 30% of blood volume (1500 mL)
Massive transfusion is ___
Massive transfusion is ≥ 1 blood volume of RBCs transfused
- About 10 units RBCs in average adult
- Hemodilution of plasma and platelets without replacement
- Current approach is 1 unit RBC: 1 unit plasma
Describe anemia compensation
Anemia compensation
- Cardiac: increased cardiac output
- Pulmonary: maintain blood oxygenation
- Vascular bed: preserve blood flow to brain and heart
- Hgb < 5 g/dL: cannot be fully compensated even when healthy but tranfuse cautiously in long-standing anemia
Most stable patients have a transfusion Hgb threshold of ____
Most stable patients have a transfusion Hgb threshold of 7 g/dL
- Higher if symptomatic anemia
- Restrictive vs liberal criteria have no effect on morbidity or 30-day mortality
In stable anemic patients, ____ between non-emergent transfusions and give only the exact number of RBCs needed
In stable anemic patients, check Hgb and clinical parameters between non-emergent transfusions and give only the exact number of RBCs needed
Describe perioperative blood management
Perioperative blood management
- Minimize blood component transfusions
- Identify and treat anemias / coagulopathies before surgery
- Judicious use in selected patients (time permitting) of preoperative autologous RBC donations or preoperative erythropoietin
- Plan and execute surgery with minimum blood loss
- Reinfuse shed RBCs from surgical field intraop/postop
Describe platelet units
Platelet units
- Plateletpheresis unit: 300 mL
- Whole blood platelet unit: 60 mL
- Stored for 5 days
___ matching to platelet gives best response when transfusing platelets
ABO matching to platelet gives best response when transfusing platelets
- D+ RBCs in platelet units might immunize D-negative patients to make anti-D
Describe response to platelet dose
Response to platelet dose
- 1/3 of transfused platelets are held by spleen
- One dose of platelets to thrombocytopenic patient increases platelet count a lot but then decreases a bit
- Circulating lifespan of 1-2 days in thrombocytopenic patients
Describe plasma products
Plasma products
- Fresh frozen plasma: separated, frozen in < 8 hours
- Plasma: frozen in < 24
Describe plasma compatibility
Plasma compatibility
- Donor has anti-A or anti-B so avoid giving anti-A/-B versus the patient’s RBC ABO type
- Group AB is universal plasma donor
___ group is the universal plasma donor
AB group is the universal plasma donor
Describe response to plasma
Response to plasma
- Plasma content concentrations measured in total plasma volume
- Plasma volume is 60% of HCt
- One unit of plasma is 200 mL (6% of total plasma volume)
- ≥ 3-4 units needed for significant clotting factor deficiency
Describe clotting factor half lives
Clotting factor half lives
- VII: 4-6 hours, vitamin K dependent (along with II, IX, X), warfarin-sensitive
- VIII: 12 hours
- Most others: 1-2 days
- Fibrinogen: 2-4 days
Describe cryoprecipitate
Cryoprecipitate
- Protein precipitate involving fibrinogen, FVIII, and vWF form
- 15 mL bag of cryo from one unit of zFFP
- Usually 400 mg fibrinogen/bag
- Adult dose is 5 bags (75 mL, 2000 mg fibrinogen)
- Ideal response is 65 mg/dL rise in fibrinogen concentration
Describe transfusion doses
Transfusion doses
- Platelets: one dose - mostly single unit apheresis
- Cryo: one dose - five bags per dose
Describe platelet counts
Platelet counts
- 150,000-400,000/uL: normal
- <75,000-100,000/uL: need for CNS hemostasis: bleeding or invasive procedure
- <50,000/uL: need for hemostasis: bleeding or invasive procedure
- <10,000/uL: risk of spontaneous bleeding
In immune thrombocytopenia purpura, ___ and tranfuse only in ___
In immune thrombocytopenia purpura, autoantibodies prevent platelet count rise and transfuse only in emergency
Describe platelets for dysfunction or dilution
Platelets for dysfunction or dilution
- Antiplatelet medications, cardiac bypass, congenital platelet disorder
- Two platelet doses are 50,000-60,000/uL functional platelets
- Massive transfusion ≥ 10 units RBCs: platelet dilution, pending platelet count
Describe platelet refractoriness
Platelet refractoriness
- Normal immediate response: platelet count rise is 25-30K/uL
- Refractory: repeated immediate responses ≤ 10 K/uL
- Non-immune reasons: splenomegaly, consumption, high turnover, large blood volume
- Test for antibodies
- Use ABO matched platelets
Describe indications for platelet transfusions
Platelet transfusion indications
- Multiple clotting factor deficiencies and need for hemostasis: bleeding or invasive procedure
- Liver disease
- Disseminated intravascular coagulation
- Emergency warfarin reversal
- Massive transfusion ≥ 10 units of RBCs and 1:1 RBC units : plasma units
- Congenital factor deficiencies when specific factor concentrate is not available
INR measures ___ and ___ is therapeutic range
INR measures factors II-VII-IX-X defieciency and 2.0-3.0 is in therapeutic range
Hemostasis is generally adequate with ___
Hemostasis is generally adequate with 30% of normal factor levels
- PT 1.5 times normal
- PTT 1.5 times normal
Describe the effect of plasma on INR
Effect of plasma on INR
- Highly elevated INR: very low factors, plasma transfusion readily improves INR
- Modestly elevated INR (~1.6): very difficult to reduce further with plasma transfusion
Complete normalization of INR with plasma transfusion ____
Complete normalization of INR with plasma transfusion often cannot be done
Describe cryoprecipitate indications
Cryoprecipitate indications
- Normal fibrinogen: 200-400 mg/dL plasma
- Hypofibrinogenemia and need for hemostasis: not responding to plasma (normal fibrinogen levels), transfusion threshold is plasma fibrinogen < 100 mg/dL
- Obstetrical bleeding: transfusion threshold < 150-200 mg/dL
- Congenital dysfibrinogenemia and need for hemostasis is rare
Describe fibrinogen concentrate
Fibrinogen concentrate
- Plasma-derived pharmaceutical
- Pathogen-inactivated
- Used in many countries to treat low fibrinogen
- Ready to use without thawing
- Approved for congenital hypo and dysfibrinogenemias
