A10. Blood transfusion

A blood transfusion is a medical procedure in which a patient is administered a blood product. The most common indication of blood transfusion is blood loss. However, this article will cover transfusion of other blood products as well, like fresh frozen plasma. See also transfusion reactions.

Transfusion compatibility

For transfusion of RBC products, the antigens on the RBCs of the donor blood product are important. The recipient can only receive RBC antigens which the recipient doesn’t have antibodies against. O is the universal donor because O-type RBC’s don’t have any ABO antigens.

For transfusion of plasma without RBCs (FFP, cryoprecipitate), the antibodies of the donor plasma are important. The recipient can only receive plasma which doesn’t contain antibodies against the recipient’s own RBC antigens. AB is the universal donor for plasma because plasma from a person with blood type AB doesn’t contain any ABO antibodies.

Types of blood products

The most frequently used blood products include:

Packed RBCs – for severe haemorrhage or anaemia. Usually indicated if Hb is < 9 g/dL acutely or < 7 g/dL chronically
- Washed and irradiated RBCs exist to reduce the risk for allergic reaction or transfusion-associated graft-versus-host disease
Fresh frozen plasma (FFP) – for replacement of clotting factors, in warfarin overdose, DIC, liver failure, etc.
Platelet concentrates – for severe thrombocytopaenia
Human albumin – for severe hypoproteinaemia

Whole blood

Whole blood is whole, unchanged blood. It's preserved with CPD and is rarely used, except for significant blood loss.

Packed red blood cells

Packed red blood cells (RBCs), also called erythrocyte concentrate, is blood which contains only RBCs and very little plasma. It’s produced by centrifuging blood and removing most of the plasma. Leukocytes are filtered out. Each unit of packed RBCs increases the Hb by approx. 1,0 g/dL. Preserved with CPD-A.

Packed RBCs is the most commonly used blood transfusion. It's mostly used for acute haemorrhage, hypovolaemic shock, symptomatic anaemia.

Indicated in acute anaemia with Hb < 9,0 g/dL. Indicated in chronic anaemia with Hb < 7,0 g/dL. These limits are not absolute; the clinical picture must be taken into account.

These values are slightly wrong according to uptodate, but they will ask them in the blood transfusion exam.

ABO and rhesus must be tested for compatibility.

Washed RBC concentrate

RBCs which have had the plasma, platelets and WBCs removed and replaced with saline. SAGM is used as additive. Indications:

People with IgA deficiency and anti-IgA antibodies
People at risk for allergic reactions
People with previous allergic reactions to blood products

Washing reduces risk for allergic reactions by removing all IgA or other proteins in the plasma of the blood product which the recipient could have an allergic reaction to.

Irradiated blood

Irradiation is the gamma irradiation of cellular blood products. It reduces the risk for transfusion-associated graft-versus-host disease (TA-GVHD) by destroying all WBCs. See transfusion complications for more information. Irradiated RBCs last 14 days. Indications:

Blood transfusion of relatives
Congenital or acquired immunosuppressed conditions

Fresh frozen plasma

Fresh frozen plasma (FFP) is plasma with all cells removed. Pure plasma. To lower the risk of transmitting viruses the plasma harvested from a person is stored and unused for 4 months, and the donor has to repeatedly test negative for HIV and HCV for these 4 months. If always negative the FFP can be given.

Indications:

Warfarin overdose
Clotting factor deficiency
- Cirrhosis
- DIC
Congenital coagulation factor deficiency
Massive transfusion

ABO must be tested. Rhesus not necessary to test.

Cryoprecipitate

Contains clotting factors. Fibrinogen, factor VIII, factor XIII, vWF and fibronectin. Produced by centrifugation of FFP. Lower volume than FFP.

Indications:

Similar as for FFP, but better if large transfusion volumes are undesirable
Fibrinogen supplementation
Factor VIII supplementation
Coagulation factor deficiency
- Cirrhosis
- DIC

Platelet concentrate

Platelet concentrate is simple, it's a concentrate of platelets indicated for thrombocytopaenia.

White blood cell products

White blood cell products are rarely used because their utility is uncertain and their risk for complications are high. The lecture lists the following indications:

Severe bacterial infection
Neonatal sepsis

Complications:

Frequent!
Anaphylaxis
Respiratory distress syndrome
+++

Storage of blood products

Storage temperature	Blood product	Storage time
22°C	Platelets	5 days
22°C	Granulocytes	24 hours
4 °C	Packed RBCs	35 days
4 °C	Washed RBCs	24 – 48 hours
4 °C	Irradiated RBCs	14 days
-18 – -25 °C	FFP	3 months
< -30 °C	FFP	2 years

Preservation of blood

During storage the:

Lactate concentration increases
Extracellular potassium increases
Ammonia concentration increases
Glucose concentration decreases
pH decreases
2,3-DPG decreases
ATP decreases

Blood needs to be preserved correctly to keep the blood viable for transfusion without damaging the blood and while keeping it sterile. There are two types:

Use of blood preservative solutions
- Anticoagulant preservative solutions – to prevent coagulation and preserve viability
  - Storage time 28 days
  - ACD
    - Anticoagulant citrate, dextrose
  - CPD (most commonly used)
    - Citrate – chelates calcium -> prevents coagulation
    - Phosphate – helps ATP production, maintains pH
    - Dextrose – energy for RBCs
    - (Adenine) – improves ATP availability for RBCs, but can cause hypotension
- Additive solutions
  - Gives storage time of 35 days
  - For packed RBCs
  - Lowers the viscosity of packed RBCs
  - Provides nutrients for RBCs after plasma is removed (plasma usually contains nutrients)
  - SAGM
    - Saline
    - Adenine
    - Glucose
    - Mannitol
Deep freezing (cryopreservation)
- Additives must be added to prevent freezing-induced damage
  - Glycerol
  - DMSO
- Blood product is first washed repeatedly, then frozen
- Advantages
  - Long-term storage
- Disadvantages
  - High RBC loss during washing
  - Expensive

Pathogens in blood

In plasma
In RBCs
- Plasmodium (malaria)
- Babesia microti
In WBCs
- HIV
- EBV
- CMV
- Toxoplasma gondii