An exchange transfusion requires that the patient's blood be removed and replaced. In most cases, this involves placing one or more thin tubes, called catheters, into a blood vessel. The exchange transfusion is done in cycles, each one usually lasts a few minutes.
The patient's blood is slowly withdrawn (usually about 5 to 20 mL at a time, depending on the patient's size and the severity of illness). An equal amount of fresh, prewarmed blood or plasma flows into the patient's body. This cycle is repeated until the correct volume of blood has been replaced.
After the exchange transfusion, catheters may be left in place in case the procedure needs to be repeated.
In diseases such as sickle cell anemia, blood is removed and replaced with donor blood.
In conditions such as neonatal polycythemia, a specific amount of the child's blood is removed and replaced with a normal saline solution, plasma (the clear liquid part of blood), or albumin (a solution of blood proteins). This decreases the total number of red blood cells in the body and makes it easier for blood to flow through the body.