Blood products

ABO system

Consists of three allelic genes - A, B and O
A and B genes control synthesis of enzymes that add carbohydrate residues to cell surface glycoproteins
The O gene is an amorph and does not transform the glycoprotein
Six possible genotypes but only four phenotypes
Naturally occurring antibodies are found in the serum of those lacking the corresponding antigen.

ABO blood group system

Phenotype Genotype Antigens Antibodies Frequency (%)

O OO O Anti-A, Anti-B 46

A AA or AO A Anti-B 42

B BB or BO B Anti-A 9

AB AB AB None 3

Blood group O = universal donor
Blood group AB = universal recipient

Rhesus system

Rhesus antibodies are immune antibodies requiring exposure during transfusion or pregnancy
85% population are rhesus positive
90% of Rh-negative patients transfused with Rh-positive blood develop anti-D antibodies

Cross Matching

Blood grouping

Patients red cells grouped for ABO and Rhesus antigens
Serum tested to confirm patients ABO group

Antibody screening

Detects atypical red cell antibodies in recipients serum

Crossmatching

Tests donor red cells against patients serum

Blood products

Whole blood
Packed red cells
Granulocyte concentrates
Platelet concentrates
Human plasma - fresh frozen plasma / freeze-dried plasma
Plasma protein fraction
Human albumin 25%
Cryoprecipitate
Clotting factors - Factor VIII / IX
Immunoglobulins

Complications of blood transfusion

Early

Haemolytic reactions (immediate or delayed)
Bacterial infections from contamination
Allergic reactions to white cells or platelets
Pyogenic reactions
Circulatory overload
Air embolism
Thrombophlebitis
Citrate toxicity
Hyperkalaemia
Clotting abnormalities

Late

Infection - cytomegalovirus / hepatitis
Immune sensitisation
Iron overload

Acute haemolytic or bacterial transfusion reactions

Due to acute haemolysis or bacterial contamination
Difficult to differentiate on clinical grounds
May occur after infusion of small volume of incompatible or infected blood
Associated with high morbidity and mortality
In unconscious patient bleeding due to DIC may be only sign
Most ABO mismatched transfusions are due to human error
Usually occurs soon after start of transfusion
Patient feels unwell and agitated
Symptoms include back pain and pain at infusion site
Associated with shortness of breath, rigors
Examination will show hypotension, oliguria and bleeding from venepuncture sites
Urinalysis will show haemoglobinuria

Management

Discontinue transfusion immediately and remove giving set
Check unit of blood against patients identity
Give intravenous crystalloid
Consider transfer to the intensive care unit
Take blood for FBC, plasma haemoglobin, clotting, blood cultures and repeat grouping
Give broad spectrum antibiotics
Monitor urine output and ECG

Anaphylaxis

Usually occurs soon after start of transfusion
May be seen in IgA deficient patients reacting to transfused IgA
Presents with circulatory collapse and bronchospasm

Management

Discontinue transfusion and remove giving set
Maintain airway and give oxygen
Administer adrenaline, chlorpheniramine, salbutamol
If the patient is IgA deficient any further transfusion must be carefully planned

Non-haemolytic transfusion febrile reaction

Usually occurs more than 30 minutes after start of transfusion
Patient feels generally well but may be shivering
Temperature is usually less than 38.5 °C
Blood pressure is usually normal

Management

Stop transfusion and assess possibility that this may be a more significant reaction
Restart transfusion at a slower rate
Consider the use of paracetamol
Hydrocortisone should not be routinely used during a transfusion

Transfusion related acute lung injury

Occurs following administration of plasma-containing blood components
Due to interaction of donor antibodies with recipient white cells
The clinical pictures is similar to ARDS
Occurs 30 minutes to several days after transfusion
Clinical features include fever, cough and shortness of breath
Chest x-ray shows perihilar shadowing
Treat as ARDS

Delayed haemolytic transfusion reaction

Occurs 5-10 days after transfusion
Clinical features are usually minimal
Possibly unexplained pyrexia or jaundice
Unexplained drop in haemoglobin
Urinalysis shows urobilinogenuria

Management

Check LFTs, clotting and red cell antibody screen

Autologous transfusion

Is the use of the patients own blood
Particularly useful in elective surgery
Accounts for 5% of transfusions in USA
Reduces the need for allogeneic blood transfusion
Reduces risk of postoperative complications (e.g. infection, tumour recurrence)
Three main techniques are:
- Predeposit transfusion
- Intraoperative acute normovolaemic haemodilution
- Intraoperative cell salvage

Predeposit transfusion

Blood collection begins 3-5 weeks preoperatively
Between 2 and 4 units are often stored
Last unit collected more than 72 hours preoperatively
Eliminates the risk of viral transmission
Reduces the risk of immunological transfusion reactions
Reduces risk of postoperative immunosuppression seen with allogeneic transfusion
Collection is expensive and time-consuming
Only suitable for elective surgery

Intraoperative acute normovolaemic haemodilution

Whole blood is removed at start of operative procedure
Between 1.0 and 1.5 litres can be collected
Replaced with crystalloid or colloid solution
Few detrimental effects of acute anaemia have been demonstrated
Blood is stored in theatre at room temperature
Blood is re-infused during or immediately following surgery
Cheaper than predeposit transfusion
Little risk of administrative or clerical error
Suitable for elective or emergency surgery at which considerable blood loss anticipated

Intraoperative cell salvage

Shed blood is collected from operative field
Blood is anticoagulated with citrate or heparin and filtered to remove debris and clots
Cells are then washed with saline and concentrated by centrifugation
Concentrate is then reinfused
Large volumes of blood can be salvaged
Salvaged blood is not haemostatically intact
Platelets and clotting factors are consumed
Suitable in cardiac or trauma surgery
Contraindicated in contaminated operative fields and in the presence of malignancy

Bibliography

Regan F, Taylor C. Blood transfusion medicine. Br Med J 2002; 325: 143-147.

Sloop G D, Friedberg R C. Complications of blood transfusion. How to recognise and respond to non-infectious reactions. Postgrad Med 1995; 98: 159-162.

Vanderlinde E S, Heal J M, Blumberg N. Autologous transfusion. Br Med J 2002; 324: 772-775.

Winkelstein A, Kiss J E. Immunohematologic diseases. JAMA 1997; 278: 1982-1992.