Blood Groups & Blood Transfusion

Agglutinogens

• Antigens present on cell membrane of RBCs

Agglutinins (Antibodies)

• Antibodies against agglutinogens, present in plasma

Agglutination

• Clumping of RBCs due to antigen-antibody reaction

Blood Grouping System

Depending upon type of agglutinogens present

1. Major blood group systems – worst transfusion reaction

• Classical ABO system
• Rh system

2. Minor blood group systems – small population

• MNS system
• P system

3. Familial blood group systems – few families

• Kell, Duffy, Lutheran, Lewis, Deigo, Kidd etc

Landsteiner’s Law

It was given by Karl Landsteiner in 1900

It has 2 parts

1. If an agglutinogen is present, the corresponding agglutinin must be absent in plasma
2. If an agglutinogen in absent , the corresponding agglutinin must be present in plasma

Note: Applicable to only ABO blood group system

Classical ABO Blood Grouping System

Agglutinogens ( A & B agglutinogens)

• They are antigens present on the cell membrane of RBCs

Agglutinins (Anti A - α & Anti B - β agglutinins)

• They are antibodies present in the plasma
• They are IgM type – cannot cross placenta

Types of ABO Blood Groups

Based on the presence or absence of A & B agglutinogens and α & β agglutinins, there are 4 types of blood groups

 

 

Determination of ABO Blood Groups

• Mix one drop of suspension of red cells with a drop each of anti-serum A, anti-serum B
• Anti-serum A will cause agglutination (clumping of RBCs) having A antigens & Anti-serum B will cause agglutination (clumping of RBCs) having B antigen

Rh Blood Grouping

• It was first discovered in Rhesus monkey hence called Rhesus factor (Rh factor / Rh antigens/ Rh agglutinogens)
• It is of 2 types – Rh +ve (Positive)  & Rh –ve (Negative)
• There are no natural antibodies (Anti-D) for Rh
• Anti-D produced only when Rh+ve  blood transfused to Rh-ve , Rh-ve mother - Rh+ve baby
• Anti-D is IgG type – cross placenta & cause Hemolytic disease of new born

Inheritance of Rh Antigens

Rh +ve – Genotype DD, Dd

Rh –ve – Genotype dd

Phenotype - DD,Dd, dd

Cross matching

• Major cross matching – Donor cell & recipient blood
• Minor cross matching – Donor blood & recipient cell

Haemolytic disease of new born

Incompatiability of Rh blood groups (Not ABO)

Mechanism of Haemolytic disease of new born

• Entrance of Rh+ve fetal RBCs into Rh-ve mother’s circulation during first pregnancy.
• Production of Rh antibodies (anti-D) in mother.
• Rh incompatibility reaction during second pregnancy

Manifestations of haemolytic disease of new born

• Anaemia – excessive haemolysis of RBCs
• Jaundice – excessive formation of bilirubin due to excessive haemolysis of RBCs
• Liver & spleen enlarge
• Excess bilirubin enters brain - disturbance of motor activity
• Intrauterine death or infant dies within few hours

Prevention & treatment

Prevention

• In Second pregnancy, it can be avoided by injecting single dose of Rh antibodies – Rh immunoglobulin, soon after child birth
• Rh antibodies destroys Rh+ve RBCs of fetus

Treatment

• by Replacement of baby’s Rh+ve blood with Rh-ve  – exchange transfusion

Clinical application of Blood Grouping

In blood transfusion – cross matching

Preventing haemolytic disease

Paternity disputes, (DNA finger printing)

Medico-legal cases

Knowing susceptibility to disease

• O : Duodenal ulcer
• A : Ca stomach, pancreas, salivary glands
• B : Diabetes

Blood transfusion

Life saving measure, should be carried out only if absolutely essential

Indications

• Blood loss - accidents, major operations etc.
• For quick restoration of Hb – severe anaemia
• Exchange transfusion
• Blood diseases – aplastic anaemia
• Acute poisoning – carbon monoxide poisoning

Donor & Recipient

• Donor – donates blood
• Recipient – receives blood

Precautions for selecting donor

• Healthy, 18 to 60 yrs
• Pregnant, Lactating – No
• Screed for AIDS, viral hepatitis, malaria & syphilis
• Hb & PCV within normal range

Precautions during blood transfusion

Absolute indication

• Cross matching – Major & Minor (Rh +ve blood never be transfused to Rh-ve person)
• Donor’s blood screened
• Blood bag/bottle should be checked
• Transfusion at slow rate
• Proper aseptic measures
• Careful watch

Hazards of Mismatched Blood transfusion

Agglutination of RBCs → Tissue ischemia → Hemolysis → Haemoglobinaemia & haemolytic jaundice → Renal vasoconstriction → Circulatory shock (loss of RBC, release of toxins– fall in BP –↓RBF) → Renal tubular damage → Acute renal shut down → Uraemia → Coma and death

Other complications of Blood Transfusion

• Circulatory overload
• Transmission of blood borne infections
• Pyogenic reaction
• Allergic reactions
• Hyperkalaemia 
• Hypocalcaemia – tetany
• Reduced tissue oxygenation – stored blood having RBC with less oxygen binding capacity

Storage of blood for transfusion

• 1 unit blood (420ml) at a time, every 6 months
• Blood + ACD mixture & stored in sterile container
• ACD mixture
• Acid citrate – 0.48 g
• Trisodium citrate – 1.32
• Dextorse – 1.47 – energy for Na+-K+ pump
• Distilled water 100ml
• Up to 21 days