56 Rh Immune Globulin (RhIg)

Principle

Rh Immune Globulin is a concentrate of predominantly IgG anti-D derived from pools of human plasma. It is available in three dosage forms; 120 micrograms (600 IU), 300 micrograms (1500 IU), 1000 micrograms (5000 IU). This anti-D provides passive protection against the formation of “immune” anti-D in patients who may be exposed to the “D” antigen. The protective effect of RhIg on D-negative individuals exposed to D-positive cells probably results from interference with antigen recognition in the induction phase of primary immunization.

It can also be used to increase platelet counts in non-splenectomized Rh positive patients with idiopathic thrombocytopenic purpura (ITP) and to alleviate clinical signs of bleeding in this patient population. The antibody in ITP is usually IgG. The antibody has broad reactivity against platelets. If there is a high concentration of antibody the platelets will not survive, therefore the passive antibody protects the platelets in circulation)

Indications and Clinical Use

Obstetrical Patients

RhIg is given to provide passive immunity against the D antigen in Rh-negative women with no evidence of previous anti-D allo-immunization.

1. Rh negative women delivering a Rh positive baby, regardless of ABO group of infant. This should be given within 72 hours of delivery. Dosage depends on the volume of fetal red cells in maternal circulation.
   1. 0.0% to 0.2% of FMH (fetal maternal hemorrhage) 1 vial of 120 micrograms
   2. 0.0% to 0.5% of FMH 1 vial of 300 micrograms
2. Rh negative women at <>28 weeks gestation if the baby’s father is Rh positive or Rh is unknown. Specimen for ABO, Rh and antibody screening must be current, test performed  prior to RhIg administration. Dosage is 300 micrograms. Passive anti-D may be detected if an antibody screen is performed one month from the date of administration. Nova Scotia has a standardized testing approach for Rh “indeterminate” prenatal patients; information is available at the Rh Program website athttp://rcp.nshealth.ca/rh
3. Rh negative women for any of the following; Dosage =1 vial of 300 micrograms

1. 1. Spontaneous or induced abortion, ectopic pregnancy, partial molar pregnancy:
      1. • Less than or equal to 12 weeks give 120 micrograms;
         • Greater than 12 weeks give 300 micrograms
   2. Amniocentesis, cordocentesis, chorionic villus sampling
   3. Obstetrical manipulation, which may result in a trans- placental hemorrhage, abdominal trauma: give minimum 120 micrograms in combo with Kleihauer.
   4. Antepartum bleeding (threatened abortion): Repeat every 6 weeks if bleeding continues. Kleihauer test for episodes in 2nd/3rd trimester

Treatment of Immune/Idiopathic Thrombocytopenic Purpura (ITP)

Receipt of Rh Positive Platelets for Rh negative individuals

Rh negative women, age 50 or less, and Rh negative males 18 years of age or younger in whom there is no evidence of D immunization should be issued RhIg when receiving Rh positive platelets (this is because of the transmission of some red cells along with the platelets being transfused). 120 micrograms covers up to 12 transfused platelets. 300 micrograms covers up to 30 platelet units and protects up to 4 weeks.

Receipt of Rh Positive Blood for Rh negative individuals

Administer 20 micrograms of RhIg per ml of rbc’s given. See RhIg product insert for limitations.

Notes

1. Some of the following terminology can be used when documenting on requisitions for some of the following circumstances:
   1. Weak anti-D due to RhIg
      1. Weak anti-D demonstrable, probably passively acquired: Rh Immune globulin issued on:__________________
   2. Initial prenatal of Rh negative mothers
      1. This patient is currently a candidate for RhIG Administration at 28 weeks gestation. A repeat antibody screen test is required before 28 weeks( it can be a few weeks before) and found to be negative for immune Anti-D prior to the receipt of Rh immune globulin.