Blood Groups andClotting

DN8

Viv Rolfe

Summary

• Blood transfusion– History of transfusions and what they are

used for.– ABO blood group system.– Rhesus blood group system.

• Mechanisms of blood clotting

Why give blood?

Why give blood? Because it saves lives.

0

5

10

15

20

25

Percent

Blood Use

General surgery

General medical

Cardiothoracic

Orthopedics

Blood diseases

Casualty

Renal

Neonates

Intensive care

How it is used?

•Whole blood - in extreme emergencies of huge blood loss.

•Red cells - anaemia, burn victims, cancer, sickle cell disease.

•Platelets - bone marrow failure, leukaemia patients, chemotherapy.

•Fresh plasma - blood loss after childbirth, major surgery.

•Processed plasma - e.g. factor VIII for treatment of haemophilia.

Blood Typing

Blood types must be matched for donation to be successful.

Blood Typing

• Many different ways of classifying blood.• Easily tested for using commercially available kits.

– ABO/Rhesus both based on the types of ANTIGEN and

ANTIBODY in the blood.

Antigen and Antibody

ANTIGENA molecule on the

surface of foreign cells (bacteria, viruses)and our own cells(blood, immune)

ANTIBODYAn immunoglobulin protein secreted byour immune system

to bind to (and combat) antigen.

ABO System

Based on the types of

1. Antigen markers on red blood cells.2. Antibodies in the plasma.

What are the 4 types?

What type are you?

UK Distribution

• A = 42%

• B = 8%

• AB = 4%

• O = 46%

A antigens B antigens Both Neither

ABO Types of Antigen

ABO Types of Antibody

Blood Transfusions-Donation of red blood cells

Type A blood CAN BE GIVEN to a Type A patient.(B to B, AB to AB and O to O).

A A

Anti-B

A

DONOR RECIPIENT

•Type A blood CAN’T BE GIVEN to a Type B patient.•Donated red cells are attacked by recipient’s anti-A antibody in their plasma.

Anti-A

A B

DONOR RECIPIENT

O can be given to EVERYONE(universal donor)

OA B

AB

O

O cells have no ANTIGEN

AB can receive from EVERYONE(universal recipient)

O

A

B

AB

AB

Incompatibility

• Reacting cells clump together or AGGLUTINATE.

• Can block capillaries stopping the blood flow.• Red blood cells finally rupture -

HAEMOLYSIS - releasing HAEMOGLOBIN which is toxic.

• Can cause kidney damage and shock (loss of blood to vital organs) and can be fatal.

ABO Interactions

Blood Type Compatible donor

Incompatible donor

A A, O B, AB

B B, O A, AB

AB A, B, AB, O None

O O A, B, AB

Universalrecipient

Universaldonor

Need the same

donor or O

Summary

A

AB

B

O

Rhesus System

1. First identified in Rhesus monkeys.

2. Based on the Rhesus antigen on red blood cells.

• Rh + people have Rh antigen (85% UK population)• RH - don’t (15% population) BUT CAN DEVELOP

ANTIBODY IF EXPOSED TO RH+.

So What?

• Complications can occur during pregnancy. A Rh- mother with Rh+ baby are at risk….

• Rh- mothers can destroy the baby's blood if this is the 2nd or 3rd pregnancy.

• The baby may have to receive a blood transfusion immediately after birth.

http://nobelprize.org/medicine/educational/landsteiner/index.html

HAEMOSTASIS stopping bleeding

Haemostasis

• Important to stop haemorrhage.

• Must remain localised.

• 3 stages:

1. Vascular spasm

2. Platelet plug formation

3. Blood coagulation (clotting)

1 Vascular Spasm

• Blood vessels contract.

• Reduces blood loss for up to 30 minutes.

http://www.mhhe.com/biosci/esp/2002_general/Esp/folder_structure/tr/m1/s7/trm1s7_3.htm

2 Platelet Plug Formation

• Plug to prevent blood loss in small vessels.

Serotonin (5-HT) causes vasoconstriction.Thromboxane A2 causes further platelet aggregation.

Platelets release chemicals

3 Blood Coagulation

• Blood thickens forming a gel/clotto prevent loss.

• Vitamin K essential for blood clotting.

• Chemical reactions for blood clotting are very complex and involve CLOTTING FACTORS.

Prothrombin activator

Extrinsic pathway Intrinsic pathwayOccurs in seconds.Triggered by enzymes “outside” the blood.FACTOR 3 and 7

Occurs in minutes.Chain reaction triggered“within” the blood.FACTOR 11 and 12

Prothrombin Thrombin

Dense Fibrin Threads

FACTOR 13

FACTOR 10

Fibrin

And afterwards…

• Fibrin clot retracts pulling the damagededges together.

• The blood clot dissolves.

Problems - Thrombosis

• Clot forms in a blood vessel e.g. deep vein thrombosis in legs.

• Can cut off oxygen supply causing tissue damage.

• Some might dislodge forming an EMBOLUS which can block smaller vessels in the brain or lungs (pulmonary embolism).

Anticoagulants

Warfarin - prevents prothrombin formation

Heparin - inactivates thrombin

Streptokinase - dissolves clots “clot buster”