What is blood?
Blood is referred to as a ‘circulating tissue’ of the body. The average adult has about five litres of blood flowing through their blood vessels. Blood is made up of many specialised cells suspended in a liquid called plasma.
Blood cells are produced by bone marrow which is the soft, spongy centre found inside most bones. As individual blood cells wear out they are continually replaced by new cells made in the bone marrow.
There are three major types of blood cells:
- Red Blood Cells (also known as erythrocytes)
- White Blood Cells (also known as leukocytes)
Red Blood Cells (RBC)
- RBCs are responsible for carrying oxygen from the lungs to all parts of the body. They are bright red in colour and usually last about 120 days after release from the bone marrow.
- To measure the amount of RBCs in the blood we determine the Haemoglobin (Hb) level. RBCs are filled with Haemoglobin, a molecule that contains iron. It is the iron in haemoglobin that binds to oxygen, allowing RBCs to carry oxygen around the body. It is also the iron that gives blood its red colour.
- A normal Hb in childhood is around 10-14 grams per 100ml of blood. A packed red cell transfusion may be given if the Hb is less than 70 - 80 grams/litre of blood.
- A child with too few red blood cells will be “anaemic” – symptoms include fatigue, loss of energy, no appetite, dizziness and/or breathlessness.
White Blood Cells (WBC)
- WBCs can be thought of as the soldiers that fight infections and are a vital part of the immune system. WBCs not only destroy germs but also remove dead or injured cells in the body.
- There are many different types of WBCs but one of the most important is the Neutrophil (or granulocyte). Neutrophils destroy bacteria in the body and help prevent septicaemia (blood poisoning).
- Another important WBC is the Lymphocyte which has an important function in fighting viruses and producing antibodies. Acute Lymphoblastic Leukaemia, is a cancer of the lymphocytes.
- The neutrophil numbers may be expressed as a percentage of the total white cell count. If a child with a low neutrophil count develops a fever or becomes sick in any way then they need to be taken to the nearest emergency department for treatment immediately.
- A child who has a low number of healthy white blood cells is at risk of infection. Although it is possible to transfuse white blood cells, it is not commonly done as they only last for a few hours after transfusion and the process can be associated with potentially serious side effects.
- The main function of platelets is to help the blood to clot. When a blood vessel is damaged (for example if you cut yourself), large numbers of platelets gather at the site of the damage. A chemical called thrombin is activated, which makes the platelets sticky and allows them to temporarily seal off the leak. Eventually a clot forms to stop the bleeding (this is called coagulation).
- A child who has inadequate platelets (‘thrombocytopenia’) may have unexplained bruises, nose bleeds, bleeding gums or petechiae (small red dots on the skin). They are also at risk of spontaneous internal bleeding.
- Platelet transfusions are usually given if the child has a low platelet count, if there is evidence of active bleeding or when the risk of bleeding is high.
There are many blood components available for transfusions but the products most commonly transfused at the Kids Cancer Centre are packed red blood cells and platelets. Packed cells are red blood cells prepared from whole blood by removing some of the plasma. Platelet transfusion packs are prepared by separating out the platelets from whole blood.
Why would my child need a blood product transfusion?
Many children treated by the Kids Cancer Centre will require the infusion of blood products at some stage during their therapy. This is due to one or a combination of the following factors:
- The child’s primary disorder causes decreased production of blood cells or proteins
- The child’s primary disorder causes excessive destruction or consumption of blood cells
- Chemotherapy interferes with the bone marrow production of blood cells.
Possible side effects of a blood transfusion
- Allergic-type reactions are seen after about 1% of blood transfusions, increasing to around 10% in those patients who are repeatedly transfused. Signs include fevers, itchiness and rash/hives. These side effects can be controlled with medications such as paracetamol, antihistamines or hydrocortisone. If a child has a history of repeated reactions, they may be given these medications prior to being transfused.
- Infection – blood can harbour bacteria. However the risk of developing a bacterial infection from a blood transfusion is very small due to strategies such as filtering, irradiating (to kill organisms) and refrigerating blood products prior to use.
Viruses can be transmitted via blood or body fluids. However, sophisticated testing of donated blood is conducted for all the significant viruses known of before any blood product is dispatched. Also, any person at risk of these infections is prevented from donating their blood.