Concerns on the Role of Blood Transfusion in the Management of Sickle Cell Disease – SCiF 2013

Graham R. Serjeant, Sickle Cell Trust (Jamaica)

 Blood transfusion with matched blood of a normal haemoglobin (AA) genotype in homozygous sickle cell (SS) disease can achieve two functions, increasing the oxygen carrying capacity when this is markedly reduced and also diluting the circulating HbS containing red blood cells.  Common indications for the former are the acutely lowered haemoglobin levels of acute splenic sequestration and the aplastic crisis and the chronically lowered levels in chronic renal failure.  There is general agreement that such transfusion can reduce morbidity and mortality and improve the quality of life.  Transfusion is also widely used in attempts to inhibit vaso-occlusion by diluting circulating HbS-containing cells and there is evidence that this can reduce the frequency of initial and of recurrent stroke and possibly retard the development of chronic pulmonary disease.  There is general agreement on these indications.  Exchange transfusions can sometimes reverse the pathology of acute pulmonary sequestration.  However, transfusions are often advocated to increase steady state haemoglobin levels prior to surgery, in the management of pregnancy and when, in the opinion of some doctors, haemoglobin levels are lower than they should be.  There still seems to be some magic belief that the haemoglobin level should exceed 10 g/dl.  Sickle haemoglobin within the red cell behaves with a low oxygen affinity becoming nearly fully saturated in the lungs but releasing more oxygen per gram of haemoglobin in the periphery than HbA.  This rightward shift in the oxygen dissociation curve implies that one cannot equate haemoglobin level with oxygen carrying capacity especially since patients with the lowest steady-state haemoglobin levels tend to have the greatest shift in dissociation curve suggesting that the erythropoietic drive may be switched off by near normal oxygen delivery.  There is a major controversy on the role of transfusion at steady state haemoglobin levels.  As with any therapy, the advantages must be balanced against the potential disadvantages.  For transfusion, these dangers are well documented and include transfusion acquired infections, red cell alloimmunisation, delayed haemolytic transfusion reactions and for chronic transfusion programmes, maintenance of venous access and iron overload.  With sophisticated facilities and at great cost, these dangers can be reduced but not eliminated but most countries where sickle cell disease is a major health problem have limited resources.  This need not imply an inferior medical practice but does infer the need for convincing evidence of clinical benefit to justify the use of these limited resources.  Often this evidence is lacking and alternative therapies may be available which can achieve the same objectives but without subjecting the patient to the delivery of foreign proteins and its associated dangers

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