MODEL RELEASED. Blood transfusion clinic. Nurse adjusting connections in the blood-filled tubing and blood bags attached to a stand during a blood transfusion. Elevating the blood bags above the patient allows gravity to be used to provide the pressure to add the blood to the patient's bloodstream. Blood transfusions are carried out to replace blood in people with blood disorders, or those who have lost blood through trauma or surgery. The blood group and type needs to be matched to that of the patient. Common blood disorders that can require regular transfusions include thalassaemia, anaemia and haemophilia.