Without a doubt, almost all people living with sickle cell disease have chronic anaemia – the haemoglobin levels at baseline vary from one individual to another. Acute anaemia is not uncommon among patients living with sickle cell anaemia.
The baseline haemoglobin level depends on a variety of factors, including the haemoglobin genotype, past and present treatments, nutrition status, among others.
What is crucial for the health care provider is to know the steady-state haemoglobin level for a particular patient to enable them to monitor and manage any complication appropriately. It, therefore, calls for the establishment and maintenance of the sickle cell clinics around the country and ensure that they are well-staffed with continuous professional development among workers.
For patients with sickle cell anaemia, their typical baseline haemoglobin levels range from 6 to 8 g/dL. Those with HbSC have 10-12 g/dL and those with HbSβ+ – thalassemia have between 9 and 12g/dL.
It is effortless to define acute anaemia if the baseline haemoglobin level for a patient in question known. We define acute anaemia as a decline by 2.0 g/dL or more in haemoglobin concentration below the patient’s baseline value.
There are various causes of acute anaemia in sickle cell disease: the common ones include sequestration in the spleen, lungs or liver, aplastic crisis, and malaria, as well as helminth infestation, especially in the tropics, where malaria is endemic, and accelerated hemolysis due to a delayed transfusion reaction, septicemia, GI bleeding, papillary necrosis or any other acute infection. It is prudent to recognize that a decline in the haemoglobin level may be the initiating event in acute chest syndrome.
Estimating the haemoglobin level at admission is not enough. It is paramount to carry out a complete blood count (CBC) to assess all the blood cells. However, it is a must to add a reticulocyte count to the CBC because of its ability to evaluate and differentiate the different possible causes of acute anaemia.
Reticulocytes are the immature red blood cells that are released by the bone marrow. Their percentage or absolute numbers directly correlate with the functionality of the bone marrow. In aplastic crisis due to Parvovirus B19 infection, they are scanty.
Sickle cell nephropathy leading to renal failure causes a slow but progressive decline in haemoglobin levels, so this should put health care providers on the alert such that this devastating condition doesn’t get them offside.
That said, let’s get to the recommendations about the management of acute anaemia in sickle cell disease, adapted from the NHLBI.
- During an acute illness in people living with sickle cell disease, obtain a CBC and reticulocyte count, repeat daily in all hospitalized patients, compare the results with the patient’s prior measurements.
- Assess people with SCD whose haemoglobin concentration is 2 g/dL or more below their baseline (or less than 6 g/dL when the baseline is unknown) for acute splenic sequestration, an aplastic episode, a delayed hemolytic transfusion reaction, ACS, and infection.
- Use simple transfusion in people with SCD and acute anaemia whose symptoms are due to anaemia.
- Perform a CBC and reticulocyte count promptly and again 7 to 10 days later in siblings and others with SCD who had exposure to a person with an aplastic episode.
- Manage aplastic events with immediate red blood cell transfusion aimed at restoring the haemoglobin to a safe (not necessarily baseline) value. Isolation of hospitalized patients is required to prevent the spread of the parvovirus B19 to pregnant women and others with SCD or compromised immunity.
It is prudent to know that aplastic anaemia in sickle cell disease is almost always due to parvovirus B19, which is highly contagious through air droplets. This virus causes Fifth disease in children among the general population; however, these children tend to fend it off due to the strong immunity and the anaemia observed is mild because of the relatively higher haemoglobin levels among the children in the general population. The virus attacks the erythroid precursors that produce red blood cells. It is so severe in sickle cell disease that death will ensue is management isn’t prompt.
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Next is a discussion about acute splenic sequestration.