Harvard Medical School, Boston, MA, USA.
Blood. 2009 Dec 10;114(25):5117-25. doi: 10.1182/blood-2009-05-220921.
Twenty-four percent of sickle cell disease (SCD) patients have a stroke by the age of 45 years. Blood transfusions decrease stroke risk in patients deemed high risk by transcranial Doppler. However, transcranial Doppler has poor specificity, and transfusions are limited by alloimmunization and iron overload. Transfusion withdrawal may be associated with an increased rebound stroke risk. Extended blood typing decreases alloimmunization in SCD but is not universally adopted. Transfusions for thalassemia begun in early childhood are associated with lower rates of alloimmunization than are seen in SCD, suggesting immune tolerance. Optimal oxygen transport efficiency occurs at a relatively low hematocrit for SCD patients because of hyperviscosity. Consequently, exchange rather than simple transfusions are more effective in improving oxygen transport efficiency, but the former are technically more demanding and require more blood units. Although viscosity is of importance in the noncerebral manifestations of SCD, inflammation may play a larger role than viscosity in the development of large-vessel stroke. The future of SCD stroke management lies in the avoidance of transfusion. Hydroxyurea and anti-inflammatory measures may reduce the need for transfusion. Recent genome-wide association studies may provide methods for modulating fetal hemoglobin production enough to attenuate stroke risk and other complications of SCD.
24%的镰状细胞病（SCD）患者在 45 岁前会发生中风。通过经颅多普勒超声检查，认为高风险的患者可以通过输血来降低中风风险。然而，经颅多普勒超声的特异性较差，且输血会受到同种免疫和铁过载的限制。停止输血可能会增加中风复发的风险。扩展血型鉴定可以减少镰状细胞病患者的同种免疫反应，但并未被普遍采用。在儿童早期开始的地中海贫血输血与 SCD 相比，同种免疫反应发生率较低，这表明存在免疫耐受。由于血液黏度增加，SCD 患者的最佳氧运输效率出现在相对较低的血细胞比容。因此，与单纯输血相比，交换输血更能有效提高氧运输效率，但前者在技术上要求更高，需要更多的血液单位。尽管黏度在 SCD 的非脑部表现中很重要，但炎症在大血管中风的发展中可能比黏度发挥更大的作用。SCD 中风管理的未来在于避免输血。羟基脲和抗炎措施可能会减少输血的需求。最近的全基因组关联研究可能为调节胎儿血红蛋白的产生提供方法，以减轻中风风险和其他 SCD 并发症。
