Sickle cell disease (SCD) remains one of the most common inherited disorders on the globe. Since its inception, blood transfusion remains pivotal therapy in the management of such patients. Before the advent of hydroxyurea, voxelotor, and the mind-boggling on-going CRISPR/Cas9 sickle cell trial, blood transfusion was the first therapy that reverses the effects of SCD. Patients living with SCD are at risk of recurrent fatal anaemia besides other common complications like a vaso-occlusive crisis.
Blood transfusion ameliorates such effects by reducing the percentage of abnormal haemoglobin (HbS) levels. It is because donated red cells contain normal haemoglobin (HbA). It is worth noting, though, that as blood transfusion reduces many complications of SCD, it also carries with it all its known adverse effects – only amplified! Clinicians should discuss the benefits and risks when they prescribe red blood cells to patients living with SCD.
The unconventional properties that sickled red cells possess promote undesirable changes within the blood vessels that culminate in such cells clogging in the microvasculature environment (vaso-occlusion). Such blood in the affected people becomes more viscous as these cells abnormally interact with other blood components. Such components include platelets, white blood cells, clotting factors, and the lining of the vessels (vascular endothelium).
Because blood transfusion is now part of SCD management globally, it’s imperative to understand the ever-increasing reasons for transfusion with evidence. It’s also paramount to get well-versed with the risks associated with recurrent blood transfusions.
To prevent alloimmunisation, people living with SCD receive leukocyte reduced and sickle negative red blood cells. In addition, to the rhesus D compatibility checks, technicians must match such blood for other minor rhesus and Kell antigens.
People living with SCD receive red blood cells either through simple or exchange blood transfusion. The difference between the two is that, for simple transfusion, the patient gets the red cells without initially removing their blood cells – whereas, for exchange transfusion, clinicians remove the sickled red cells and replace them with normal red cells.
Because exchange transfusion removes sickled red cells from the patient, it increases the percentage of normal red cells. It also allows an increased amount of blood that clinicians can transfuse without necessarily increasing the patient’s blood volume above levels dangerous to the heart. The net transfused blood also reduces – further decreasing the risks of iron overload. The downsides are:- increased exposure to donor blood which may potentiate the risks of alloimmunisation; higher costs; the need for specialised equipment; and permanent venous access.
Episodic blood transfusion happens due to an acute complication like acute anaemia or as preparations for surgery. Chronic transfusion occurs for primary or secondary complications of SCD like, stroke. When used appropriately, blood transfusion is life-saving and may protect against organ damage.
A multitude of indications for a blood transfusion exists among people living with SCD. We shall discuss each of them in the subsequent article series as we unravel this life-saving therapy.