255. Blood Transfusions - Indications

Question 1

What is the typical adult blood volume? How much is RBCs?

How much is 1 RBC unit? What is the Hb response in 1 RBC unit?

Answer 1

Total BV: 5000mL
(2000mL RBC, 3000mL plasma)

One Unit = RBC from 500mL whole blood collection (gets centrifuged)

• 300mL packed RBC = 180 mL pure RBC
• 1g/dL rise in Hb per unit RBC

Question 2

Indications for RBC transfusions (3)

• Hb threshold, exceptions
• 3 physiologic compensations for anemia

Answer 2

1. Acute bleeding (when blood loss = 30% blood volume ~1500mL; Massive Transfusion > 1 blood volume or > 10 units, causes hemodilution of plasma/platelets need to add)
2. Low-production anemia (correct underlying cause too)
3. Perioperative blood management

Cardiac: increase CO
Pulm: Maintain blood O2
Vascular Bed: preserve blood flow to brain, heart

Stable pt: transfuse at/under 7g/dL Hb
Threshold for cardiac problems (MI/ACS) and thrombocytopenia: 8g/dL

Transfuse one RBC unit at a time

Question 3

What are the three types of non-RBC blood components?

- types, storage, response

Answer 3

1. Platelets
   - plasmapheresis unit (300mL) vs Whole blood platelet unit (60mL)
   - lasts 5 days!! (SHORT)
   - response: immediate platelet rise 25-30K/uL, after 24hrs rise is only 10-15K/uL (1-2day lifespan)
2. Plasma
   - FFP: frozen <8hr, lasts longer
   - Plasma: frozen <24hr (most plasma)
   - one unit = 200mL (need 3-4+ units for significant clotting factor deficiency)
   - duration for clotting factor short (1-2 days most factors, F7 = 4-6hrs, F8 = 12hrs)
3. Cryoprecipitate
   - FIBRINOGEN, F8, vWF
   - lasts 1 year frozen, <6hrs when thawed
   - usual content: 400mg/bag (15mL); adult dose is 5 bags = 75mL and 2000mg fibrinogen
   - ABO matching NOT NEEDED (just factors)
   - response: 65mg/dL rise in fibrinogen conc (half life 2-4 days)

Question 4

Indications for Platelet Transfusion (5)

Answer 4

1. <10K - prophylaxis due to risk spont bleed
2. <50K and need for hemostasis (bleeding/invasive procedure
3. 50K-100K and need for CNS hemostasis (bleeding/invasive procedure for CNS = higher threshold)
4. Platelet dysfx and need for hemostasis (post-procedure, congenital platelet disorder, hemorrhagic stroke on antiplatelet meds)
5. Massive RBC > 10unit transfusion (need to prevent platelet dilution)

Question 5

Indications for Plasma (3)

Answer 5

1. Multiple clotting factor deficiencies and need for hemostasis: liver disease, DIC, emergency warfarin reversal, massive transfusion >10RBC units
2. Congenital factor deficiencies when specific factor concentrate is not enough (US has specific factors for everything except F5, F11)
3. TTP
   - target INR 2.0-3.0
   - practical limit of correction 1.6 due to dilution

Question 6

Indications for Cryoprecipitate (3)

Answer 6

1. Hypofibrinogenemia and need for hemostasis (<100mg/dL)
2. Obstetrical bleeding <150-200mg/dL (higher threshold)
3. Congenital dysfibrinogenemia and need for hemostasis (rare)