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Therapeutic Apheresis FAQs
What is Apheresis?
Blood is made up of a number of different components:
- Red blood cells, which carry oxygen around the body.
- White blood cells, which help to prevent and fight infections.
- Platelets, small particles which help the blood to clot.
- Plasma, the liquid part of the blood in which many proteins and other substances are dissolved.
Some diseases are caused by excessive numbers of these cells and by abnormalities of the proteins and other substances dissolved in the plasma. One way of treating these diseases is to temporarily remove blood from the body and to separate the blood into its components. The unwanted component can then be discarded, before returning the other components to the body. Although only a small volume of blood is removed from the body at any one time, large quantities of blood can be processed in this way, leading to a significant reduction in the level of cells or substances responsible for the disease. This process is called apheresis and is accomplished by means of a special machine called an apheresis machine or a cell separator. Because apheresis can also be used to collect blood cells and plasma from normal blood donors, the term therapeutic apheresis is used when this process is used to treat a disease.
Why are Therapeutic Apheresis procedures performed?
These procedures are performed either for harvesting of cells for donation to another individual, for retransfusion to the same individual after treatment or for experimental research. Human plasma could be harvested in this fashion, but this is not the usual means of obtaining fresh plasma. Additionally, apheresis is performed for therapeutic reasons. The rationale for treating a patient with apheresis is determined by his/her particular diagnosis.
What does Apheresis involve?
Blood is removed from a vein and mixed with a substance to stop the blood clotting while outside the body. In most cases the substance used is citrate. This binds calcium, which is essential for clotting of blood. The blood is then processed by the apheresis machine to separate the various components, allowing the unwanted component to be discarded and the remaining components to be returned to the patient. This requires one or two needles to be inserted into the veins, usually one in each arm. In some patients with small arm veins it may be necessary to insert a special catheter into the large veins under the collarbone or in other parts of the body to allow adequate blood flow for the procedure. If insertion of a special catheter is required, separate information about this procedure will be given and separate consent will be obtained.
What types of Therapeutic Apheresis services exist?
- Plasmapheresis
- Cytadepletion
- Leukapheresis
- Plateletpheresis
- Erythrocytapheresis - Red Cell Exchange
- Stem cell harvesting
- Photopheresis
- LDL-Apheresis
How much time does it take to complete a treatment?
Each procedure takes several hours, the actual time depending on a number of factors including the disease being treated, the size of the patient, the type of machine being used, the vascular access, patient's hemodynamic stability, patient's hematocrit, blood flow rate and plasma flow rate all contribute to the length of the treatment. Treatments are prescribed in volumes of plasma to be exchanged. Generally, a four-liter exchange will take about two-and-a-half (2 1/2) hours, with a range of one to four (1-4) hours.
How often should Apheresis be performed?
There is generally no magic number of procedures that should be performed for a given patient. In many cases, the patient is reevaluated after 2 or 3 procedures to see if they are responding. For many diseases, such as the neurologic syndromes, the clinicians have set formulas that they follow. This is fine, as long as it seems reasonable. For example, they may do 5 procedures over two weeks. Other times, the procedure is done daily until the patient improves (examples: TTP and ABO-incompatible liver transplant rejection. Improvement in the patient with TTP is followed by monitoring the platelet count and the LDH level. The liver transplant patient has serial antibody titers followed). Some procedures are one time only -- for example, leukoreduction and red cell exchange are done one time in most patients. Only rarely is a second leukoreduction needed, although the WBC values may not drop as much as desired after one procedure. The extent of the drop in WBC count cannot be predicted after apheresis. If the patient is producing a lot of WBCs, the count may not drop much and may even rise after pheresis. Therefore, the number of treatments required is dependant on a number of factors, but treatments are usually initially provided every 1-2 days.
What are the possible complications of performing Therapeutic Apheresis?
- Some minor problems are occasionally caused by the insertion of the needles in the arms, including pain, bruising, infection and minor damage to the nerves of the skin.
- Tiredness, dizziness and fainting can occur sometimes.
- Nausea, cramps, and tingling in the fingers or around the mouth may occasionally be experienced. These symptoms are usually caused by the citrate that prevents the blood from clotting while outside the body. It is infused into the patient with the components that are not discarded, but the body rapidly removes citrate from the blood stream, usually making this a very brief phenomenon. It can generally be overcome by slowing the rate of return of the components or by giving calcium, either by mouth or (rarely) by infusion into the blood stream.
- All the tubing, needles and bowls used in this process are sterile and disposable. A new apheresis set is used for each procedure, avoiding any problems of contamination.
- Reactions to the replacement fluids occur occasionally. These are more common when fresh frozen plasma is used, but serious reactions are rare. Rare theoretical risks include the possibility that air might be introduced into the patient's blood stream but modern apheresis machines include alarms to prevent this and patients are monitored very closely during the procedure.
- Infection.
- Hemorrhage.
- Cardiac irritation from central line catheter and/or citrate infusion directly into right atrium.
- Hemolysis.
- Air embolism.
What is the difference between Therapeutic Apheresis and Dialysis?
Therapeutic Apheresis and Dialysis are very similar procedures but very distinct differences that separate the two procedures. In Dialysis, the liquid is extracted from the central line in the body. Going in through the central line allows for a greater flow rate resulting in a quicker procedure - 30 to 45 minutes. The difference in apheresis is that the liquid is extracted from the veins causing a slower flow rate and a longer procedure.
Can a patient undergo Dialysis and Apheresis on the same day?
Dialysis and apheresis can (although it is not recommended) be performed on the same day. If these two procedures were to be done on the same day, it is recommended that apheresis be performed first.
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