Information for patients, relatives and carers. This information will help you understand about having a red cell exchange transfusion and simplify any questions you may have about this procedure. For further information please talk to your sickle cell doctors or clinical nurse specialist.

What is a Red cell Exchange Transfusion (RET)?

An RET is a procedure that delivers fresh donor red blood cells into your blood stream and removes the old sickle cells. By reducing the number of sickle cells. It helps to increase the amount of oxygen delivered, aid circulation and prevent or treat complications due to sickle cell disease. This could be a planned procedure or be performed in an emergency situation.
The total volume of blood required for RCEx transfusion is calculated based on your weight, the percentage of sickle cells in your blood and the desired level that the sickle level should be reduced to.

There are two ways to perform this procedure; either by using a special blood cell separator machine (automated) or manually removing the blood from the patient using a big syringe.
A planned RET can be done in the Haematology unit of your local hospital or if an emergency, it can be performed on the ward as an inpatient.

An automated exchange using the blood cell separator will be performed either peripherally via a cannula in each arm or by a big femoral line inserted into your groin. Once access has been obtained then you will be connected to the machine by a qualified nurse and the donor red blood cells will be checked against your details. then the exchange will begin. The Automated device uses a centrifuge to separate your blood components .It removes approximately half a unit (250 mls) of blood that is centrifuged (spun) and then the red cells are discarded. The plasma is returned to your circulation at the same time as donor red cells are given. This spin procedure is repeated several times. The nurses will continually monitor your Vital signs i.e . Blood pressure (BP); Pulse, Respiration rate and temperature as well as side-effects to transfusion.

For a manual exchange you will have a cannula inserted into one arm for replacement fluids e.g. blood or saline and a venesection (blood removal) will be taken from the other arm. A venesection is to remove a unit of whole blood (approximately 500mls) into a bag for disposal. This is followed by transfusion of one unit of packed red blood cells (about 300 mls). The cycle of blood removal and transfusion may be repeated up to 4 times depending on your blood counts, replacing each unit of blood removed with a unit transfused. Once the entire calculated donor blood volume has been used up, the procedure will end. The nurse will then apply pressure dressings to both exit sites to prevent any bleeding. Blood samples will then be sent off to determine the Haemoglobin level as well as the new sickle percentage.
For both methods the same volumes of blood are removed as are replaced with blood or fluids so as to keep a stable blood pressure.

What is blood?

Blood is the red liquid that circulates in the blood stream and contains different types of blood cells all carried in plasma (a straw like colour) which is the buffer for all blood cells.
The blood cells carried are:

• Red cells: contain haemoglobin which is the red pigment carrying oxygen to the tissues and carbon dioxide removed from the tissues of the body.
• White cells: these help to fight infection
• Platelets: help with clottin

The adult human body contains about 5 litres of blood on average but depends on your height and weight. Normally red cells last in the blood stream for up to 90 to 120 days but in sickle cell patients , the red cells last only 10-20 days

In sickle cell disease removal of old red cells is not as effective as in a healthy person. The remaining red cells in the blood stream can cause problems. Therefore the RET helps to remove these abnormal cells from the circulation.

Is it safe to have a blood transfusion?

In the UK all units of blood donated are screened making them as safe as possible for transfusion. There is a small risk that the blood may be contaminated with hepatitis B in about 1 in 900,000 or hepatitis C 1 in 30 million or Human immunodeficiency virus (HIV) 1 in several million. Because of these risks, sickle patients patients are advised to receive full hepatitis B vaccination. Patients on regular transfusion also have virology screen will be taken yearly to check this risk factor. We recommend that you should be vaccinated against hepatitis B so you develop immunity. Ask your nurse or doctor for the blood transfusion leaflet by the NHS for more information or look at the national blood service website.

The main risk from a transfusion is that human error can occur possibly given the wrong blood by accident. The nurses will thoroughly check the blood is right for you before starting the RET by checking with you your details and checking the documentation. If there are any concerns on any unit of blood, it will be sent back to blood bank.

What are the benefits – why should I have an exchange transfusion (RET)?

A single RET may be undertaken for an emergency situation such as acute sickling in the lungs ( acute chest syndrome ) or prior to some planned operations .Some patients are selected for a long-term transfusion programme ( ie repeated every 4-6 weeks for several months or years ). They may have severe sickle cell disease with complications or repeated pain crises. Sickle cells are regularly removed to try and prevent further complications.

The aim of the ET is to reduce your sickle cells in the blood but is unable to reduce them altogether. You will still have an increased risk of infection and the transfusion will not reverse any chronic damage. It is not a perfect treatment but may reduce the chances of any new serious problems occurring.

What are the possible side effects?

The side-effects to be aware of during an automated RET are that you could have a mild reaction to the anticoagulant used for the flow of blood in the machine. This can cause a tingling sensation around the mouth as your calcium level drops during the procedure. Please inform your nurse if this happens as calcium tablets or an infusion will be required to resolve the problem.

There is a risk that if the procedure is run too fast you may drop your blood pressure and feel light-headed then the machine will be slowed down and more intravenous fluids will be given.

There is also a risk that you may develop an allergic reaction to the blood causing fever and chills, rashes, shortness of breath or extremely rarely anaphylaxis .If you have had problems with blood transfusions before then medications will be given to you to prevent a reaction. Please inform your nurse if any of these side-effects have occurred before.
With a manual exchange you may become light-headed that could lead to fainting but the replacement fluids should prevent this happening.

For both procedures there is a risk of iron building up in the body causing iron overload .This is more common in people who have regular top up transfusions rather than exchanges. This may require iron chelation therapy .

If you regularly have an ET it is possible that you may develop antibodies against the donor blood but the blood is matched as closely as possible. These antibodies are not harmful but if you do develop anti-bodies it can become harder to match your blood, as this is one way your body reacts to foreign blood. Please inform your nurse if any of these problems have occurred.

Are there any alternatives?

One alternative at present is Hydroxyurea (Hydroxycarbamide) an oral medication only for specific sickle cell related complications. The other alternative is simple top-up transfusion. Discuss with clinic doctors and the clinical nurse specialist for haemoglobinopathies for further information.

Is there anything I should do to prepare for exchange transfusion?

You will need to have a blood test for cross match either 24 or 48 hours beforehand depending on your cross-match requirements

Blood bank can prepare the amount of blood needed for the exchange usually 8-10 units matching as closely as possible to your blood group and checking if you have developed antibodies. We will also check other routine bloods to check if you are well enough to go ahead with the procedure. If you are unable to make the appointment please call your Haematology hospital team as soon as possible to arrange another date. If you do not let them know you are not attending then the blood will be wasted and as well as an appointment that could have been given to someone else. If you miss your RET, you may become unwell before another slot is arranged for you.

Asking for your consent

Before the procedure you will be asked for your consent to go ahead with the ET and for a femoral line insertion if needed. They will give you relevant information to help you come to a decision with the Red cell team. It is important that you understand about the procedures before consenting. If you agree you will be asked to sign a consent form for both the ET and each femoral line insertion. This will be reviewed in clinic regularly. If you are on a regular ET programme and wish to stop then please discuss this with the sickle team regarding other suitable treatments that can be offered to you and make clear the implication on your health of the decision you have taken to stop the RET programme.


What happens on the day of exchange?

On average the automated ET using the cell separator will take up to 2 to 4 hours. This depends on the condition your health is in at that time; for example the RET will be slower if you are pregnant (due to the risk to the baby) or if you have previously had a reaction to the procedure.

Expect the procedure to take all day therefore please arrange your activities around the procedure to keep the day free for any unexpected problems and recovery post the procedure.


Having a femoral line inserted?

If your arm veins are difficult to access from previous use, you will be given the option to have a femoral line inserted into your groin to help with the flow of blood for the procedure. A femoral line is a large cannula inserted into your femoral vein in your groin under a sterile environment either in angio suite or on the Day unit. We will rotate sites between left and right groin at each visit to try and prevent scar tissue developing.

You will be given the choice to have sedation medication to help you relax for the procedure .This excludes pregnant women. If you choose this option you will be advised not to have breakfast that morning in order to reduce the risk of aspiration with sedation.

. The sedation will make you drowsy rather than send you to sleep as it is different to general anaesthetic. Therefore be prepared mentally for the procedure. On average it can take about 30 minutes to prepare for the insertion as a small cannula will need to be inserted in your arm so that the sedation can be given.

The femoral line may then take only 10 minutes to insert. Sometimes stitches will be placed to stop the line falling out. From patient feedback we are aware that this insertion can be painful. Before insertion local anaesthetic will be applied to the groin area. Please be aware that this can sting for a short while before the numbness occurs.


Can I have an RET without the femoral line?

If your veins are large enough cannulas will be inserted into each arm one for access to draw out your blood and one for return of the donor blood. This usually takes longer and if either cannula fails another cannula will need to be inserted..

If you have manual exchanges cannulas will be inserted. This is the old-fashioned way and takes much longer. The post exchange Hb S% may not be as lowas expected as this method is not as effective.


What happens after the exchange?

When the exchange is finished you will wait for 30 minutes so your body can adapt to the changes. Blood samples will be taken to check that your counts are within range. If the bloods are within range the femoral line and cannulas can be removed. Once removed, the nurse will apply pressure to the exit sites until the bleeding has stopped and dressings will be applied to the area to prevent further bleeding. Then you will need to remain lying down for some time as if you get up too soon bleeding may occur immediately. You may also feel dizzy. The time to apply pressure as well as the period for observation are usually longer for patients who had Femoral lines removed.
After this period the nurse will return to check the area and your vital signs to check if you are well enough to go home.

Exchange Transfusion

If you have received sedation, you must not drive home and will need someone to collect you. If you have not had sedation you should be safe to travel on public or own transport.

We recommend that you go home and rest for that evening. If you feel well enough the next day you can return to your normal routine.

Upon discharge the nurse should give you the date of your next exchange transfusion appointment if required. If another appointment is not booked then please contact the clinical nurse specialist or Day care as soon as possible to arrange.


Please see the following video links for further information

A Fresh Breath of Oxygen: Red Blood Cell Exchange Transfusion in Sickle Cell and COVID-19 - link

Exchange transfusion video - link

Blood Transfusions: How, Why, and When? - link

What Are Blood Transfusions - link

Transfusion Challenges in Haemaglobinopathy Sickle cell and Thalassaemia - link