Blood Transfusion - Part 1

Blood is liquid tissue. It is comprised of several types of blood cells suspended in plasma.

5 litres in circulation


Composition of blood

• RBCs (erythrocytes)
• WBCs (leukocytes)
• Granulocytes
• Neutrophils
• Eosinophils
• Basophils
• Agranulocytes
• Lymphocytes
• Monocytes
• Platelets (thrombocytes)

Haematocrit is usually 45%

Suspension in test tube:

• Plasma above
• White blood cells in the middle "Buffy coat"
• Red blood cells below

Functions of blood

• Transport
• O2 and CO2
• Food molecules (e.g. glucose/lipids/amino acids)
• Ions (e.g. sodium, potassium, calcium)
• Waste products (e.g. urea)
• Hormones
• Blood clotting factors (platelets and plasma)
• Heat (blood also helps maintain its constant body temperature)
• Immune system
• Defence against infection and other foreign materials
• Many different types of white blood cells participate in forming body's defence system against infections but most critical of these are neutrophils and lymphocytes

Anaemia

• Drop in red blood cells
• Drop in haemoglobin in red blood cells

Main causes

• Nutritional deficiency
• Such as iron, vitamin B12 or folate
• Replace
• Blood loss
• Such as significant amount of surgical bleeding, trauma, internal bleeding from stomach or bowel
• Treat cause
• Salvage
• Transfuse
• Failure of production of red blood cells by bone marrow
• Such as patients with leukaemia and those receiving chemotherapy
• Transfuse
• Erythropoietin to increase production

Platelets

• 20-50 x 10^9/L
• Drops in
• Viral infections
• Autoimmune thrombocytopenia (ITP)
• Failure of production of platelets in the bone marrow
• Platelets may be reduced following massive haemorrhage requiring replacement of 2 or more blood volumes

Plasma components

• Water (90-93%)
• Proteins (6-9%)
• Salts (0.7%)
• Lipids (0.6%)
• Glucose (blood sugar) (0.1%)