Transfusion therapy (Sickle-cell disease)

Red blood cells (erythrocytes) from donors contain normal hemoglobin (HbA), and transfusion of normal red blood cells into people with sickle cell disease reduces the percentage of red cells in the circulation containing the abnormal hemoglobin (HbS).^[1] Although transfusion of donor red blood cells can ameliorate and even prevent complications of sickle cell disease in certain circumstances, transfusion therapy is not universally beneficial in sickle cell disease.^[2]

Types of transfusion therapy

There are two main types of transfusion, simple red cell transfusion and exchange transfusion.

Simple transfusion

Involves transfusing red blood cells without removing any of the patient’s blood.^[3]

Exchange transfusion

Exchange transfusion involves removal of the patient’s blood and replacement with donor red blood cells.^[3]

There are three main benefits of an exchange transfusion compared to a simple transfusion, these relate primarily to the ability to remove hemoglobin S containing red blood cells:

1. Higher percentage of normal (donor) hemoglobin (HbA) containing red cells after the transfusion
2. Larger volumes of donor blood can be given without increasing the hematocrit to levels that excessively increase blood viscosity
3. Reduced net transfused volume of red blood cells, which reduces iron overload.^[3]

However, there are also potential risks associated with an exchange transfusion:

1. Red cell alloimmunization due to increased donor exposure
2. Higher costs
3. Need for specialized equipment
4. Need for good venous access.^[3]

Automated red cell exchange

The exchange is performed using a machine (pheresis). This method rapidly and substantially reduces the concentration of sickle cells within the blood without increasing the overall hematocrit or blood viscosity.

Manual red cell exchange

The exchange is performed manually. It refers to manually phlebotomizing a percentage of the patient’s blood prior to or concomitantly with giving a red cell transfusion.

Frequency of red cell transfusions

Red cell transfusions can be further classified as episodic or chronic.^[3]

Episodic transfusion

Episodic transfusion is used either acutely in response to a complication of sickle cell disease such as acute chest syndrome or to prevent complications prior to surgery.^[3]

Chronic transfusion

Chronic transfusion is used when sustained, low levels of HbS are needed to prevent sickle cell-related complications, most commonly stroke in children.^[3]

Indications for red blood cell transfusion

Transfusion therapy for sickle-cell disease entails the use of red blood cell transfusions in the management of acute cases of sickle cell disease and as a prophylaxis to prevent complications by decreasing the number of red blood cells (RBC) that can sickle by adding normal red blood cells.

Prevention of complications

Stroke

In children prophylactic chronic red blood cell (RBC) transfusion therapy has been shown to be efficacious to a certain extent in reducing the risk of first stroke or silent stroke when transcranial Doppler (TCD) ultrasonography shows abnormal increased cerebral blood flow velocities. In those who have sustained a prior stoke event it also reduces the risk of recurrent stroke and additional silent strokes.^[4][5][6]

Surgery

In children and adults red blood cell transfusion to increase the hemoglobin level to 100 g/L has been shown to decrease the risk of sickle cell-related complications.^[2] However, this has not been seen in all studies.^[7]

Treatment of complications

Splenic sequestration

Acute splenic sequestration associated with severe anemia requires a simple transfusion to raise the hemoglobin.^[3]

Complications related to red blood cell transfusion

Iron overload

Each unit of transfused blood has approximately 250 mg of iron, with each successive transfusion, patients receiving chronic transfusion therapy accumulate iron in various tissues in the body as the body has no way to excrete the excess, this is a cause of increased morbidity and mortality.^[8] The effects of iron overload are countered by chelation therapy^[9]

References

1. ↑ Drasar E, Igbineweka N, Vasavda N, et al. Blood transfusion usage among adults with sickle cell disease - a single institution experience over ten years. Br J Haematol. 2011 Mar;152(6):766-70. doi:10.1111/j.1365-2141.2010.08451.x. Epub 2011 Jan 31. PMID 21275951
2. 1 2 Yawn BP; Buchanan GR; Afenyi-Annan AN; et al. (2014-09-10). "Management of sickle cell disease: Summary of the 2014 evidence-based report by expert panel members". JAMA. 312 (10): 1033–1048. doi:10.1001/jama.2014.10517. ISSN 0098-7484. 
3. 1 2 3 4 5 6 7 8 "Evidence-Based Management of Sickle Cell Disease" (PDF). Retrieved 9 February 2016. 
4. ↑ Gyang E, Yeom K, Hoppe C, et al. Effect of chronic red cell transfusion therapy on vasculopathies and silent infarcts in patients with sickle cell disease'Am J Hematol. 2011 Jan;86(1):104-6. PMID 21117059
5. ↑ Mirre E, Brousse V, Berteloot L, et al. Feasibility and efficacy of chronic transfusion for stroke prevention in children with sickle cell disease Eur J Haematol. 2010 Mar;84(3):259-65. Epub 2009 Nov 12. PMID 19912310
6. ↑ Wang, Winfred C; Dwan, Kerry (2013-11-14). Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease. John Wiley & Sons, Ltd. doi:10.1002/14651858.cd003146.pub2. ISSN 1465-1858. 
7. ↑ Hirst, Ceri; Williamson, Lorna (2012-01-18). Preoperative blood transfusions for sickle cell disease. John Wiley & Sons, Ltd. doi:10.1002/14651858.cd003149.pub2. ISSN 1465-1858. 
8. ↑ Harmatz P, Butensky E, Quirolo K, et al. Severity of iron overload in patients with sickle cell disease receiving chronic red blood cell transfusion therapy. Blood. 2000 Jul 1;96(1):76-9. PMID 10891433
9. ↑ P. B. Walter, P. Harmatz, and E. Vichinsky, "Iron metabolism and iron chelation in sickle cell disease," Acta Haematologica, vol. 122, no. 2-3, pp. 174–183, 2009.