Blood Transfusion 1

Question 1

What is RhD positive?

Answer 1

85% of population

Carry the RhD antigen

Patients can receive RhD negative (just a waste!) or RhD positive red cells

Question 2

What is RDh negative?

Answer 2

15% of population

Lack the RhD antigen

Patients can make immune anti-D if exposed to RhD positive red cells

Question 3

What are immune anti-D antibodies?

Answer 3

Are IgG (so cross the placenta)

Do not cause direct agglutination of RBCs

Cause delayed haemolytic transfusion reaction.

There are some other Rh antigens e.g., C, c, E and e

Question 4

What are other blood groups antigens?

Answer 4

Kell (K), M, N, S, Duffy (Fy), Kidd (Jk)

But we only match for these if patient has corresponding antibody (or occasionally in certain other situations)

Question 5

Who can RhD negative cells be given to?

Answer 5

Can safely be given to anyone, but often in short supply. Occasionally (emergency/shortage) it may be necessary to use RhD-positive blood for the transfusion of RhD-negative patients, this does not cause acute problems but will sometimes induces formation of anti-D.

Will be picked up by the lab next time they need blood. RhD negative blood would then be issued. RhD negative women exposed to RhD positive blood can produce immune anti-D, which can cause haemolytic disease of the newborn or severe foetal anaemia and heart-failure (hydrops fetalis) in pregnancy.

Question 6

What are the immune antibodies involved in blood transfusion?

Answer 6

IgG

Question 7

What is antibody screening and what is screened?

Answer 7

Can’t test all other RBC antigens (100s) but about 1-3% of patients have immune RBC antibodies to one or more RBC antigen, As a result of TRANSFUSION and/or PREGNANCY.

REALLY IMPORTANT to identify clinically significant RBC antibodies and transfuse RBCs that are negative for that antigen yo prevent a DELAYED HAEMOLYTIC TRANSFUSION REACTION.

Question 8

How does antibody screening occur?

Answer 8

Use 2 or 3 reagent red cells containing all the important red cell antigens between them. Screen by incubating the patient’s plasma and screening cells using IAT technique.

Question 9

What is the IAT technique?

Answer 9

Indirect antiglobulin technique.

Bridges red cells coated by IgG, which can’t themselves bridge 2 red cells – to form a visible clump. Takes 30 mins’ incubation at 37°C.

Question 10

Why does antibody screening happen before every transfusion even if it might have been done before?

Answer 10

Because new antibodies can be made after a transfusion or in pregnancy.

Question 11

What is electronic issue?

Answer 11

Electronic issue (EI) is the selection and issue of red cell units where compatibility is determined by IT system, without physical testing of donor cells against patient plasma.

Question 12

What are the advantages of electronic issue?

Answer 12

Quicker

Fewer staff

No need to have blood “standing by” just in case

Remote issue

Better stock management

Question 13

What is serological crossmatch and how it’s done?

Answer 13

Full crossmatch:

Indirect antiglobulin technique: Patient plasma incubated with donor red cells at 37C for 30-40 mins, will pick up antibody antigen reaction that could destroy the red cells and cause extravascular haemolysis. Add antiglobulin reagent (AHG). IgG antibodies can bind to RBC antigens but do not crosslink so AHG reagent is added.

Immediate spin: Saline, room temperature. Incubate patient plasma and donor red cells for 5 minutes only and spin, will detect ABO incompatibility only. IgM anti-A and/or anti-B bind to RBCs, fix complement and lyse the cell.

Question 14

What are donor RBCs labelled with?

Answer 14

ABO and D type

Kell

Other Rh antigens

Question 15

What are the three pillars of patient blood management?

Answer 15

Optimise haemopoiesis

Minimise blood loss and bleeding

Harness and optimise physiological tolerance of anaemia

Question 16

What are steps which can be taken to achieve each of the three pillars of patient blood management?

Answer 16

Minimise blood loss and bleeding:

• Stop anticoagulation/antiplatelet agents
• Blood sparing techniques
• Tranexamic acid
• Cell salvage
• Anaemia

Harness and optimise physiological tolerance of anaemia:

• Optimise cardiac output
• Restrictive transfusion threshold

Question 17

What is the decision to transfuse based on?

Answer 17

Is the patient bleeding?

What are the blood results?

Is the patient symptomatic?

Will a transfusion solve the problem?

What are the risks of transfusion?

Are there alternative treatments?

Question 18

What information needs to be given for patient consent?

Answer 18

“Valid” consent is required for transfusion (verbal & written).

Alternatives should be considered if appropriate:

• Iron / B12 / EPO / Folate
• Cell Salvage

If transfused in an emergency, patient must be informed afterwards.

Involve patients in the process to ensure they get the right blood and the right ‘special requirements’.

Question 19

What information is kept about the donor records for blood transfusion?

Answer 19

All components are issued on a named patient basis 100% of components must be traceable from the donor to the recipient.

Records are kept for 30 years.

Question 20

How are red cells given/stored?

Answer 20

Give ABO/D compatible.

Group O (negative) in emergency.

Consider special requirements.

Stored at 4C for 35 days.

Must be transfused within 4 hours of leaving fridge.

Transfuse 1 unit RBC over 2-3 hours.

Question 21

How are platelets given/stored?

Answer 21

ABO/D antigens weakly expressed.

Should be D compatible.

Consider special requirements.

If group O given to A, B or AB patients select ‘high-titre’ negative (anti-A/B antibodies).

Stored at 20C for 7days.

Transfuse 1 unit of platelets over 20-30 minutes.

Question 22

How is fresh frozen plasma given/stored?

Answer 22

Give ABO compatible (D group does not matter).

AB plasma can be given to all groups as it has no anti-A/B antibodies but it is in short supply.

No need to cross match but does take 30-40 minutes to thaw.

Once thawed can be kept at 40C for 24 hours.

Transfuse 1 unit over 20-30 minutes.

Question 23

How is cryoprecipitate given/stored?

Answer 23

Give ABO compatible (D group does not matter).

AB plasma can be given to all groups as it has no anti-A/B antibodies but it is in short supply.

No need to cross match but does take 30-40 minutes to thaw.

Once thawed has to kept at room temperature and use within 4 hours.

Transfuse 1 unit over 20-30 minutes.

Question 24

What is the Maximum Surgical Blood Ordering Schedule (MSBOS)?

Answer 24

MSBOS is based agreement between surgeons and transfusion lab about predictable blood loss for ‘routine’ planned surgery. Junior doctors / nurses doing pre-admission clinics have some idea what is normal.

Have to be flexible if non-standard surgery or special patient requirements (e.g. bleeding disorder). Some operations rarely need blood – e.g. gall bladder op Some operations always need blood – e.g. aortic aneurysm repair.

Blood allocated to a patient, if not used are taken back into stock repeatedly.

Question 25

What is a group and save in elective surgery?

Answer 25

If no antibodies present, sample saved in the fridge.

If unexpected need for blood, can provide it within 10 minutes (by Electronic Issue, as no antibodies present).

Question 26

What is a crossmatch in elective surgery?

Answer 26

If history of antibodies or G+S picks up new antibody.

Ensure BT lab aware of date of surgery so that suitable RBC units are available.

Question 27

What are specific transfusion indications for red blood cells and their triggers?

Answer 27

Major Blood Loss: If >30% Blood volume lost

Peri-Op, Critical Care: Hb <70g/L vs 80g/L

Post Chemo: Hb <80g/L

Symptomatic anaemia: Ischaemic heart disease, breathless, ECG changes.

Question 28

What are things to be careful about when giving a blood transfusion?

Answer 28

Check Hb pre transfusion and after every 1-2 units.

1 unit RBC gives a Hb increment of 10g/L in a 70- 80 kg patient.

Transfusion to above 100g/L is rarely required, unless symptomatic or severe cardiac/respiratory disease etc.

Question 29

What are specific transfusion indications for platelets and their triggers?

Answer 29

Massive transfusion: Aim Plts >75 x109 /L

Prevent bleeding (post chemo): If < 10 x109 /L (<20 if sepsis)

Prevent bleeding (surgery): < 50 x109 /L (<100 if critical site: eye, CNS, polytrauma)

Platelet dysfunction or immune cause: Only if active bleeding

Question 30

What are things to be careful about when giving a platelet transfusion?

Answer 30

One unit of platelets is an adult treatment dose: Usually raises platelet count by 30-40 x109 /L.

Platelets are best given whilst procedure being carried out, little/no benefit in giving earlier on ward.

Question 31

When is a platelet transfusion contraindicated?

Answer 31

Heparin-induced Thrombocytopenia Thrombosis (HiTT)

Thrombotic Thrombocytopenic Purpura (TTP)

Question 32

What are indications for FFP indications and dosage?

Answer 32

Massive transfusion early infusion of FFP is recommended to treat coagulopathy. Aim to maintain PT and APTT ratio at <1.5.

Liver disease: There is no evidence of benefit from FFP in patients with a PT ratio of less than or equal to 1.5.

Replacement of single coagulation factor deficiency, e.g. factor V.

DIC in the presence of bleeding and abnormal coagulation results.

Thrombotic thrombocytopenic purpura (TTP).

4 units in 70kg man.

Question 33

What is in cryoprecipitate?

Answer 33

Fibrinogen

fVIII and vWF

Fibronectin

fXIII

Platelet microparticles

IgA

Albumin

Question 34

Can someone receive their own blood if they are a donor?

Answer 34

Pre-operative autologous deposit: Donate own blood before planned operation. Not in the UK (futile, no net gain & doesn’t avoid problems of wrong blood or bacterial contamination).

Intra-operative cell salvage: Yes - Collect blood lost during surgery: centrifuge, filter, wash & re-infuse it. Most UK surgical and obstetric units can do this.

Post-operative cell salvage: Collect blood lost post-op into wound drain – filter & re-infuse. Mainly orthopaedic (knee surgery).

Question 35

What are specific requirements for a blood transfusion?

Answer 35

CMV negative blood: Only required for intra-uterine /neonatal transfusions and for elective transfusion in pregnant women (baby in-utero is exposed to maternal transfusion).

Irradiated blood: Required for highly immunosuppressed patients, who cannot destroy incoming donor lymphocytes: which can cause (fatal) transfusion associated graft versus host disease (TA-GvHD).

Washed: Red cells and platelets are only given to patients who have severe allergic reactions to some donors’ plasma proteins.