【Abstract】 Rh(-) blood is a scarce type and plays an important role in the transfusion, hemolytic disease of the newborn, autoimmune hemolytic anemia. This review focuses on the clinical blood transfusion management in Rh(-) patients.

【Key words】Rh(-) blood; Transfusion management

Blood transfusion is an important clinical medication. The Rh system has been known to be the most impotant and complex blood system behind ABO blood system. There are over forty antigens of Rh blood system, however, the mainly antigens associated with blood transfusion include^[1] D antigen, Cw antigen, G antigen, Rhnull, Rhmod, Del and so on. The D antigen is the strongest immunogenic antigen beside AB antigen. The Rh(+) blood refers to the red blood cells that contain D antigen, the definition of Rh(-) blood is the red blood cells without D antigen vice versa. There are over 99% RH (+) pepole in China.

1 Transfusion policy in Rh(-) patients

There is no primary anti-D in Rh (-) people. The formation of anti-D is usually through transfusion, pregnancy or alloimmunization. Therefore it is difficult to discover the Rh-mismatched transfusion. When transfused antigen into body again, hemolytic reaction will occur because of anamnestic reaction by the antibody produced during first Rh-mismatched transfusion. Thus it has great importance to investigate the indications and management of clinical blood transfusion in Rh(-) patients.

  Table 1 shows the policy approved by the Transfusion Committee of the University Hospital of Salamanca in 2008 for the use of RBCs in Rh(-) patients.^[2]

There is still debate regarding whether other Rh(-) blood components must be transfused in Rh(-) patients with matched type. However, there is a consensus that it’s essential to avoid transfusion of Rh (+) blood in Rh (-) females of childbearing age, newborn and children.

2 Blood transfusion management in Rh (-) patients

It is well known the immunogenicity of erythrocytes. Recent studies have shown the risk of anti-D alloimmunization in Rh(-) healthy volunteers who received Rh (+) RBCs is approximately 80-95 percent^{[3、4、5、6、7]}. However, this rate is significantly lower among Rh (-) recepients with bone marrow transplantation ^{[8、9、10、11]}, tumors ^{[12、13、14]} and AIDS^[15].  And in nonimmunosuppressed Rh(-) patients this rate is around 20-30 percent^[16、17]. Thus it’s necessary to focus on the clinical blood transfusion management in Rh (-) patients.

2.1 The use of autotransfusion

  Humans may infect hepatitis virus, HIV or even confront trannfusion reaction with blood tranfusion. Therefore, indications of tranfusion should be strictly controlled by clinician in order to avoid unnecessary blood tranfusion. Autotransfusion is advocated allowing for the scarcity of Rh (-) blood.  In addition, autotransfusion is a technique that could ensure safe and promptly transfusion into Rh (-) patients with maximatily lower probablity of transfusion reaction.

Patient that could use autotransfusion should meet the basic criterion as follow: Hb>110g／L，Hct>0.35，PLT>100×10⁹／L，PT within normal range，heart fuction below grade III as well as without obvious liver and renal dysfunction.

2.2 The use of RhIG

Prophylaxis against Rh-mismatched transfusion is proved highly effective with timely administration of adequate Rhesus immune globulin (RhIG).^[18] Saleh Ayache^[19] has summarized from the studies of Keith^[20]、Parker^[21] the indications and highlight of RhIG medication in the conditions of Rh-mismatched transfusion with or without intention, and as elaborated below：1) Prophylaxis through RhIG should be strongly considered in case of Rh-mismatched transfusion; 2) The basal level of haemoglobin, hematocrit and bilirrubin should be monitored before RhIG medication due to its adverse effect such an decreasing hematocrit and increasing bilirrubin; 3) The dosage of RhIG depends on the volume of RBCs and whole blood; 4) Prophylaxis of a dose of 125IU or 20 ug RhIG per 1 ml of Rh(+) RBCs or per 2 ml of whole blood should be given intravenously; 5) The dose of 125 or 300ug RhIG will be sufficient to prevent alloimmunization in recipients of Rh(+) PLTs because of small Rh (+) RBCs volumes involved; 6) Although the therapeutic window is limit of 72 hours, RhIG is still effective beyond this point; 7) Antihistamines, antipyretics or steroids should be recommended accompanied with RhIG medication, in order to avoid adverse reactions such as chill, fever and headache； 8) The existence of antibodies in recipients posttransfusion should be determined by serologic testing, and recipients should be followed up for at least 6 to 8 months.

3 Discussion

  Indications of blood tranfusion should be strictly considered to avoid unnecessary blood tranfusion to Rh (-) patients. Homotypic blood should be transfused as far as possible. Unfortunately, in some situations such as massive transfusion or a shortage of Rh(-) blood, the transfusion of Rh(+) blood to Rh(-) patients may be required. If meeting the indications of Rh-mismatched transfusion^[2], Rh(-) patients should receive homotypic  Rh(+) blood in order to avoid missing the optimal medication opportunity. Rh(-) patients of AB type without anti-A、anti-B or anti-O could receive Rh(-) blood of A、B、O type in life-threatening situations

References

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