Haem 7 + 8 - Blood transfusion Flashcards
what kind of antibodies are
anti-B, anti-A ab
Anti-D ab
anti-B, anti-A ab - IgM
Anti-D ab - IgG
What kind of reaction do anti-D antibodies produce when they cross the placenta?
Delayed haemolytic transfusion reaction
Group and screen vs full Xmatch
Group and screen – check ABO group and plasma antibodies in patient
Full crossmatch – checks patient’s blood against donor blood specifically
o If no antibodies present in the patient’s blood, a crossmatch is not needed
o if antibodies are present, always crossmatch
How is the grouping of the RBC done?
both of the below are done and included in a “Group and Screen”:
o (1) Forward group – Use known anti-A, anti-B and anti-D reagents against the patient’s RBCs
o (2) Reverse group – known A and B groups red blood cells are mixed with the patient’s plasma (IgM antibodies)
This group acts as an internal control – if it does not match, this is an anomalous result
New-borns often have a weak reverse group as their antibodies have not developed fully yet
o Column agglutination technology
o Positive result = agglutination at the TOP
o Negative result = red cells stay suspended at the BOTTOM of the vial
Immune antibodies vs naturally occurring antibodies
o Immune antibodies are IgG
Cause a delayed transfusion reaction
Extravascular haemolysis
o Naturally occurring antibodies are IgM
Cause an immediate intravascular haemolysis
How do you screen a patient’s plasma for antibodies against RBC
• Antibody screen on patient’s plasma
o (1) use 2 or 3 reagent RBCs containing all important RBC antigens between them
o (2) incubate patient’s plasma and screening cells using the Indirect Antiglobulin Technique (IAT)
Indirect Antiglobulin Technique (IAT)
Patient serum containing specific antibody added to reagent RBCs
IgG antibody can attack to RBC antigens
Add Anti-Human Globulin (AHG) to promote agglutination between the IgG antibodies on the different RBC
If +ve, reaction creates bridges between RBCs coated in IgG antibodies visible clumps
Takes 30 mins incubation at 37oC
What are the two types of serological crossmatch and how are they carried?
• Serological crossmatching checks the blood against the donor’s blood specifically
o Full Crossmatch (uses IAT (Indirect antiglobulin technique)):
Patient’s plasma is incubated with donor red cells at 37oC for 30-40 mins
Detects antibody-antigen reaction that destroys the RBCs leading to extravascular haemolysis
IgG antibodies bind to RBCs but do not crosslinking add antiglobulin reagent to cause cross-linking
Agglutination/haemolysis = incompatible
o Immediate Spin [emergency scenario only]:
Saline, room temperature
Incubate patient’s plasma and donor red cells for 5 minutes only and spin
Will only detect ABO incompatibility
IgM anti-A and/or anti-B bind to RBCs, fix complement and lyse the cell
the 3 pillars of patient blood management
• Optimise haemopoiesis o Identify anaemia pre-surgery + treat IV/ PO iron – 1mg IV B12 replacement – 1mg IM hydroxocobalamin Folate replacement – 5mg PO EPO SC – preparation dependent
o Targets Ferritin 100ug/L TSATs 25-30% B12 >350 ng/L Serum folate >5 ug/L
• Minimise blood loss and bleeding o Stop anticoagulation/antiplatelet agents o Tranexamic acid – 1mg PO/IV o Blood sparing techniques o Call salvage o Prevent wastage
• Harness and optimise physiological tolerance of anaemia
o Optimise cardiac output
o Restrictive transfusion threshold for patients who are fit and healthy (Hb <80g/L)
• (avoid hypothermia, DIC/coagulopathy, electrolyte imbalance)
Which blood components need to be matched for both ABO + D?
Which blood components need to be matched only for ABO?
ABO + D
RBC
Plt
Only ABO
FFP
Cryoprecipitate
Storage of
RBC
Plt
FFP
Cryoprecipitate
RBC
4C for 35 days
if outside of fridge for >30min goes to the bin – worried about bacterial contamination
Complete transfusion should take place within 4h of leaving the fridge
Plt
20C (room temperature) for 7 days
Screened for bacteria before release
Transfuse over 20 mins
FFP
Frozen (-25C)
Once thawed can be kept at 4C for 24 hours
Cryoprecipitate
Frozen
Once thawed has to be kept at room temperature and use within 4 hours
What should happen if a patient develops temperature during a plt transfusion?
?bacterial contamination of platelets
stop the platelets
take blood cultures
send platelets back to the lab for microbiological testing
Most likely cause if a patient reacts when FFP/cryoprecipitate is being transfused?
• A reaction with plasma is more likely to be allergic as plasma is frozen and so is unlikely to be contaminated by microbes
RBC transfusion
What should happen before?
How often should Hb levels be checked?
By how much g/l does 1 unit of RBC raise Hb?
• Treat iron/folate/b12 deficiency first unless active bleeding
• Check Hb
o Pre-transfusion
o After every 1-2 units
• 1 unit RBC = Hb increment of 10g/L in a 70-80 kg patent (if the patient is not haemolysing)
o Only transfuse one unit at a time unless active bleeding
o Can be transfused “stat” but routinely would be 2-3h
Hb targets in RBC transfusion depended patients
70 g/l if asymptomatic, 80 g/l if symptomatic
o Higher threshold of up to 90-100 g/l for patients with CHD
o Transfusion to >100g/L rarely required unless
Symptomatic (IHD, SOB, ECG changes)
Severe cardiac/respiratory disease
Triggers for the following RBC transfusion indicators
Major blood loss
Pre-op, Critical care
Post chemo
Major blood loss
>30% of blood volume lost
Pre-op, Critical care
<70 or 80 g/l depending on co-morbidities
Post chemo
<80 g/l
Plt transfusion
By how much does 1 unit of plt raise plt count?
• 1 unit of platelets in an adult treatment dose usually raises platelet count by 30-40 x 109/L
Plt transfusion contraindications
o HITT (heparin-induced thrombocytopenia with thrombosis) – patients who have had a clot on UFH o TTP (thrombotic thrombocytopenic purpura)
Triggers for the following plt transfusion indicators
Massive transfusion Prevent bleeding (surgery) Prevent bleeding (post-chemo) Platelet dysfunction or immune cause Reduced platelet production (e.g. leukaemia
Platelet dysfunction can be caused by drugs (e.g. aspirin, clopidogrel)
)
Massive transfusion
Aim plt >75 x 10^9/L
Prevent bleeding (surgery)
<50 x 10^9/L
<100 x 10^9/L - if critical site - eye, CNS, polytrauma
Prevent bleeding (post-chemo)
<10 x 10^9/L
<20 x 10^9/L if sepsis
Platelet dysfunction or immune cause
Reduced platelet production (e.g. leukaemia
Only if active bleeding
FFP
What should happen before?
When should FFP be transfused?
Adult dose
when and how do you assess the effectiveness of the transfusion?
- consider using vitamin K first if appropriate
- Do not use unless patient is bleeding or undergoing a procedure e.g. surgery
Adult dose - 15-20 ml/kg
• Reassess after administration by measuring coagulation parameters
