Blood transfusion in sickle cell disease and Red cell exchange
Why might someone with sickle cell disease need a blood transfusion?
Blood contains many different cells. The red cells contain something called haemoglobin (often called Hb) that is essential for carrying oxygen around the body. Sickle cell disease is an abnormality of haemoglobin. When the body is stressed because of illness, infection, or dehydration, the red cells become crescent shaped and very sticky. This can cause the person to become very unwell. Transfusion can often reverse the sickling process particularly if some blood is take out as part of the process (exchanged). Sometimes the blood count can drop dramatically and a blood transfusion may be needed to correct it. Blood transfusions in sickle cell disease are logistically and medically more complicated that in the average person and great attention and thought has to be used in order to get things right for the patient.
What types of transfusion can be given in sickle cell disease?
There are two ways of delivering blood transfusions in sickle cell disease; top up and exchange. A top up means that only blood is given, whereas in an exchange, blood is taken out and both blood and saline (salt water) is given. This is to decrease the overall proportion of sickle cell blood. The exchange can also be split into manual (done by hand) or automated (done by a machine). Automated exchange is sometimes known as Apheresis.
Why might someone need a transfusion ?
- to treat severe anaemia.
- to prepare for an operation
- to treat a severe complication e.g. stroke or a chest syndrome.
- to prevent a severe complication e.g. stroke
- to support a patient for a short time e.g. in pregnancy or with poorly healing leg ulcers.
What choice of transfusions are there in sickle cell disease?
The choice of which to use should be based on a medical decision made with the patient.
- To correct anaemia: this is often if the blood count drops dramatically sometimes due to infection
- To decrease the proportion of sickle in the blood – here then there are three choices.
A simple top-up transfusion can be used to decrease the proportion of sickle in the blood. It is easy to give and many nurses will be trained to do this, it only needs a small vein and so is relatively uncomplicated to deliver.
However, sometimes the doctor may think that this might not reduce the proportion enough, so will not recommend a top-up and may recommend a red cell exchange instead. Also, each time you give a top-up transfusion you receive iron which is part of the red blood cell. Too much iron is bad for you and people who have had a lot of top-up transfusions need medicine (known as chelation) to take away the extra iron so it does not make them ill.
Red cell exchange transfusions are good in the sense that some blood is taken out and so less iron is given; the amount of sickle cells can be decreased more effectively and more quickly. This is a service run through Harley Street at UCLH with dedicated apheresis staff from the UCLH apheresis team.
When considering the exchanges, what is better – automated or manual red cell exchange? They both have their advantages and disadvantages. Automated is more effective in that it drops the sickle percentage much lower and much faster. Also for automated exchange, usually for every red cell you take out, you put one in such that there is no iron loading at all. However, in order to be more effective, often more blood is needed, which may lead to a delay in treatment in the emergency setting.
As it is more effective, for those on a long term programme, the gap between exchanges is longer e.g. 6-8 weeks for automated rather than 3-4 weeks for manual. This offers a real quality of life improvement for these patients as they do not need to come to hospital as often. The other thing of note is that some patients describe feeling much healthier on the automated exchange; some patients notice a real difference between the lower percentages of sickle cell blood that they get on an automated programme.
The disadvantage of automated exchange is that you need really good venous access (good fast flowing veins), often better than that you need for manual exchange. Sometimes your arm veins may not be good enough and the team may recommend central venous access with a temporary line e.g. vascath or a more permanent access e.g. a vortex port. This is when a plastic tube is inserted into a larger vein usually in the groin though sometimes in the neck. This is needed in about two thirds of patients on automated exchange and can lead to a delay in giving the treatment. However, practically, a significant proportion of patients who have manual exchanges have veins that are so poor that they would need central venous access in any case.
What can Dr Trompeter offer?
- advice regarding when and how to transfuse
- montoring the effects of transfusion
- arrange exchange and top up transfusions delineating the parameters in a tailor-made fashion