Introduction

Plasma is the fluid part of blood and makes up the bulk of the volume. It contains substances that can be used totreat a number of different conditions.

Blood is made up of four separate components, which each perform a different function. They are:

• red blood cells - carry oxygen around the body and remove carbon dioxide
• white blood cells - help the body fight infection
• platelets - tiny cells that trigger the process that causes the blood to clot (thicken)
• plasma - yellow fluid that transports blood cells and platelets around the body and contains a number of substances, including proteins

What is plasma?

Plasma is the largest component of blood, making up about 55% of its overall content. It's mainly made of water and surrounds the blood cells, carrying them around the body.

Plasma helps maintain blood pressure and regulates body temperature. It contains a complex mix of substances used by the body to perform important functions.

These substances include minerals, salts, hormones and proteins.

Three important proteins found in plasma are:

• albumin
• clotting (coagulation) factors
• immunoglobulins

How plasma components are used

Plasma components can be used in a number of different ways, depending on the condition they're being used to treat.

The two main methods of using plasma are:

• fresh frozen plasma transfusion - where plasma is separated from donated blood and frozen until needed; it's then thawed under controlled conditions and transfused to the recipient
• plasma exchange - where a special machine is used to remove plasma from the patient's blood; it's then replaced with a substitute plasma component from donors

For example, they can be usedin severe injuries when there's a lot of bleeding.

In the UK, specific clotting factors are also used to treat Haemophilia , an inherited condition that affects the blood's ability to clot.

Immunoglobulins

Immunoglobulins are part of the immune system (the body's natural defence againstinfection and illness).

Immunoglobulins are antibodies that the body produces to fight a variety of infections. For example, they're used to fight health conditions such as:

• chickenpox - a serious but usually shortlived viral infection
• hepatitis - a viral infection that causes the liver to become inflamed (swollen)
• rabies - a very rare infection of the central nervous system that's passed on to humans from infected animals

Normal human immunoglobulins can be used to support people whohave conditions where their immune system is having difficulty producing antibodies.

Plasma is the source of anti-D immunoglobulin, a substance often given by injection to pregnant women with a rhesus-negative blood group (RhD negative)whose unborn baby may have a rhesus-positive blood group (RhD positive).

This treatment prevents the mother becoming sensitised to the baby's blood and stops immune anti-D developing. Immune anti-D can cause rhesus disease in subsequent pregnancies, which is a potentially fatal condition.

Risks of using plasma components

Some people can experience problems related to a plasma transfusion.

These can vary in severity from a slight increase in temperature to the development of a serious condition called variant Creutzfeldt-Jakob disease (vCJD) in very rare cases.

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