Red blood cell transfusions are a long-standing treatment in sickle cell disease (SCD). Similar to other medical treatments, blood transfusions have risks and benefits so it is important to understand why a blood transfusion has been recommended for you or your loved one with SCD. Let's review some of the common reasons here.
The definitive treatment of stroke in sickle cell disease is a red blood cell transfusion. The treatment of a stroke in this circumstance requires a special transfusion called an exchange transfusion or erythrocytapheresis. In this procedure, blood will be removed from the patient into a machine that will separate the red blood cells from the platelets, white blood cells, and plasma.
The patient's red blood cells will be discarded and everything else will be given back plus they will receive more red blood cells. The goal of this treatment is to reduce the percent of sickle hemoglobin from >95% to < 30%.
Patients with SCD are a significant risk for surgical complications including pain crises and acute chest syndrome. The risk of these complications can be decreased with a transfusion less than 1 week before the surgery. The general recommendation is to bring the hemoglobin up to 10 g/dL. This can be achieved with a simple transfusion but some patients with higher baseline hemoglobins might need to undergo exchange transfusion as discussed above.
The need for transfusion is determined by sickle cell severity, baseline hemoglobin, and overall risk of surgery. Some more mildly affected patients may not need transfusion prior to surgery. This should be discussed with your sickle cell healthcare provider.
Acute chest syndrome is a unique complication only found in SCD. There are several causes of acute chest syndrome including infectious causes like pneumonia. Transfusions are generally used if the patient needs oxygen or if hemoglobin is lower than normal. Early transfusions can prevent progression in some patients.
If acute chest syndrome becomes severe, requiring intensive care unit (ICU) treatment, exchange transfusion is recommended with similar goals as acute stroke.
Transient aplastic crisis is triggered by infection with parvovirus B19 (a human form, not the one dogs have). Parvovirus is the cause of a childhood infection called Fifth Disease. Parvovirus prevents the bone marrow from making new red blood cells for 7-10 days which can cause severe anemia in people with SCD. This severe anemia may require transfusion until the bone marrow production returns.
Patients with hemoglobin SC disease or sickle beta plus thalassemia may not require transfusions as their baseline hemoglobin is higher than hemoglobin SS.
Splenic sequestration is an event where sickled red blood cells become trapped in the spleen and are unable to come out. This is most common in children under 5 years of age.
The spleen enlarges in size to accommodate the red blood cells and this can cause severe anemia. IV fluids and transfusion seem to stimulate the spleen to release the trapped red blood cells. Once the spleen releases the red blood cells, they return to circulation returning the hemoglobin to baseline.
In patients who have already experienced stroke or patients at high risk for stroke (as identified on transcranial doppler, TCD), a chronic transfusion program is recommended.
Clinical research trials have shown that monthly transfusions can prevent strokes from recurring or from ever occurring in high-risk patients. These recurrent transfusions reduce the percent of sickle hemoglobin in circulation, preventing further events.
There are multiple factors that go into the decision to give a blood transfusion and this list doesn't cover all the indications. Blood transfusions are not used to treat the underlying anemia seen in SCD as it is generally well tolerated. Hydroxyurea, an oral medication, is better suited for reducing anemia. As with all therapies, it is important to discuss the risk and benefits for the treatment with your physician.