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YR5 Haematology > Blood Transfusion 1 > Flashcards

Blood Transfusion 1 Flashcards

1
Q

What is the prevalence of RhD positive patients?

A

85% of population carry RhD antigen

Can receive RhD -ve (just a waste!) or RhD +ve red cells

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2
Q

What is the prevalence of RDh negative patients? What blood should they not be given?

A

15% of population lack RhD antigen

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

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3
Q

What are immune anti-D antibodies?

A

IgG (so cross placenta)

Do not cause direct agglutination of RBCs

Cause delayed haemolytic transfusion reaction.

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

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4
Q

What are the other blood groups antigens?

A

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

But only match for these if patient has corresponding antibody

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5
Q

Who can RhD negative cells be given to?

A

Can safely be given to anyone, but often in short supply.

Occasionally (emergency/ shortage) may be necessary to give RhD +ve blood to RhD -ve patients, this does not cause acute problems but sometimes induces formation of anti-D.

Will be picked up by the lab next time they need blood. RhD -ve blood would then be issued.

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6
Q

What RhD reaction may occur in pregnant women?

A

RhD -ve women exposed to RhD +ve blood can produce immune anti-D, which can cause haemolytic disease of the newborn or severe foetal anaemia + heart-failure (hydrops fetalis) in future pregnancy.

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7
Q

What are the immune antibodies involved in blood transfusion?

A

IgG

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8
Q

What is antibody screening and what is screened?

A

Can’t test all RBC antigens (100s)
but ~1-3% of patients have immune RBC antibodies to >,1 RBC antigen as a result of TRANSFUSION +/- PREGNANCY.

REALLY IMPORTANT to identify clinically significant RBC antibodies + transfuse RBCs that are -ve for that antigen to prevent a DELAYED HAEMOLYTIC TRANSFUSION REACTION. (>24h)

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9
Q

How does antibody screening occur?

A

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

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10
Q

What is the IAT technique?

A

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.

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11
Q

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

A

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

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12
Q

What is electronic issue?

A

The selection + issue of red cell units where compatibility is determined by IT system, without physical testing of donor cells against patient plasma.

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13
Q

What are the advantages of electronic issue?

A

Quicker

Fewer staff

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

Remote issue

Better stock Mx

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14
Q

What is serological crossmatch? Describe the indirect anti globulin technique for this

A

Full crossmatch:

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 + cause extravascular haemolysis.
Add antiglobulin reagent (AHG). IgG antibodies can bind to RBC antigens but do not crosslink so AHG reagent is added.
Agglutination/ haemolytic = incompatible

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15
Q

What crossmatching technique is used in acute need/ trauma cases?

A

Immediate spin technique
Saline, room temperature.

Incubate patient plasma + donor red cells for 5 mins only + spin, will detect ABO incompatibility only.

IgM anti-A +/- anti-B bind to RBCs, fix complement + lyse the cell.

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16
Q

What are donor RBCs labelled with?

A

ABO + D type

Kell

Other Rh antigens

Traceability tag

17
Q

What are the three pillars of patient blood management?

A

Optimise haemopoiesis

Minimise blood loss + bleeding

Harness + optimise physiological tolerance of anaemia

18
Q

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

A

Minimise blood loss + bleeding:
* Stop anticoagulation/ antiplatelet agents
* Blood sparing techniques
* Tranexamic acid
* Cell salvage

Harness + optimise physiological tolerance of anaemia:
* Optimise cardiac output
* Restrictive transfusion threshold

19
Q

What is the decision to transfuse based on?

A

Is the patient bleeding?

What are the blood results?

Is patient symptomatic?

Will a transfusion solve the problem?

What are the risks of transfusion?

Are there alternative tx?

20
Q

What information needs to be given for patient consent?

A

“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 + the right ‘special requirements’.

21
Q

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

A

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 30y.

22
Q

How are red cells given/stored?

A

Give ABO/D compatible.

Group O (-ve) in emergency.

Stored at 4C for 35d.

Must be transfused within 4h of leaving fridge.

Transfuse 1 unit RBC over 2-3h.

23
Q

How are platelets given/stored?

A

ABO/D antigens weakly expressed.

Should be D compatible.

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

Stored at 20C for 7d.

Transfuse 1 unit of platelets over 20-30 mins.

24
Q

How is fresh frozen plasma given/stored?

A

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 X match but does take 30-40 mins to thaw.

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

Transfuse 1 unit over 20-30 mins.

25
Q

How is cryoprecipitate given/stored?

A

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 mins to thaw.

Once thawed has to kept at room temperature + use within 4h.

Transfuse 1 unit over 20-30 mins.

26
Q

Which blood component has a higher risk of carrying infection? Why?

A

Platelets- stored at a warmer temperature

27
Q

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

A

Agreement between surgeons + transfusion lab about predictable blood loss for ‘routine’ planned surgery. Junior docs / 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.

28
Q

What is a group and save in elective surgery?

A

If no antibodies present, sample saved in the fridge.

If unexpected need for blood, can provide it within 10 mins (by EI, as no antibodies present).

29
Q

What is a crossmatch in elective surgery?

A

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

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

30
Q

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

A

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.

31
Q

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

A

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

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

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

32
Q

What are specific transfusion indications for platelets and their triggers?

A

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

33
Q

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

A

1 unit of platelets is an adult tx 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.

34
Q

When is a platelet transfusion contraindicated?

A

Heparin-induced Thrombocytopenia Thrombosis (HiTT)

Thrombotic Thrombocytopenic Purpura (TTP)

35
Q

What are indications for FFP indications and dosage?

A

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

Liver disease: No evidence of benefit from FFP in patients with a PT ratio of ,< 1.5.

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

DIC in the presence of bleeding + abnormal coagulation results.

Thrombotic thrombocytopenic purpura (TTP).

4 units in 70kg man.

36
Q

What is in cryoprecipitate?

A

Fibrinogen

fVIII + vWF

Fibronectin

fXIII

Platelet microparticles

IgA

Albumin

37
Q

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

A

Pre-operative autologous deposit: Donate own blood before planned operation. Not in 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 + obstetric units can do this.

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

38
Q

Why might those receiving cell salvage blood need other components?

A

All coagulation factors + platelets are removed

39
Q

What are specific requirements for a blood transfusion?

A

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

Irradiated blood: Required for highly immunosuppressed patients, who can’t destroy incoming donor lymphocytes: which can cause (fatal) transfusion associated GvHD (TA-GvHD).

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

YR5 Haematology (20 decks)

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