General principles

The most serious life-threatening complications occur predominantly in early childhood, although all are seen, albeit much less frequently, in adult life. The principal events in adult life requiring intensive care include the acute chest syndrome and complications occurring postoperatively or during pregnancy.

General principles of treatment include oxygenation, hydration, and maintenance of oxygen delivery. There are no risks with oxygen therapy, but there are no controlled observations confirming benefit. Hydration is important but again lacks experimental support, although the increased blood viscosity is likely to be deleterious and there is in vitro evidence that a hypertonic medium promotes sickling. High skin losses in a tropical setting, particularly with fever, inability to concentrate the urine, and reluctance or inability to drink, imply that dehydration may develop rapidly. There is sometimes reluctance to give intravenous fluid because of the belief that cardiac and renal damage diminish the patient's ability to handle a fluid load, but the dangers of dehydration are far greater. Most patients can handle fluid loads well, and intravenous fluid intakes should be at least 2 liters plus urinary output, monitored by a central venous line if there are concerns over the degree of dehydration or of overhydration. Blood transfusion may be indicated for two reasons, namely maintenance of oxygen delivery and dilution or replacement of red cells containing sickle hemoglobin (HbS). A knowledge of the patient's steady state hemoglobin level is valuable in assessing oxygen delivery. If the hemoglobin falls more than 2 g/dl below steady state levels, the underlying cause should be investigated and, if not treatable directly, may require 'top-up' transfusion. Since transfused blood of an AA genotype has a higher oxygen affinity than HbS, the aim should be to transfuse to at least 1 g/dl above the steady state hemoglobin level. If the aim is to replace HbS-containing cells, this is best achieved by exchange tranfusion which is most simply performed by removing 500 ml of blood followed by the transfusion of 2 units and repeating the procedure after 4 h.

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