(Written with assistance from Thomas Doyle, MS, CCP)
I. GENERAL INFORMATION:
Erythroblastosis Fetalis is a process relating to a blood incompatibility disorder. This disorder is characterized by the mother rejecting the fetus due to an incompatibility of blood group types caused by previous pregnancy or blood transfusions. Gamma globulin’s are transported across the placenta and attach themselves to antigenic sites on the fetal red blood cells. Fetal erythrocytes are thus sensitized and removed from the circulation by the fetal reticuloendothelial system thus creating an anemia. The term erythroblastosis fetalis originates from the fact that during this removal process, the hemoglobin concentration in the patient falls due to the accelerated red cell destruction. New red blood cells are produced by the fetus in an attempt to correct the anemia that has been created. Due to the excessive production of erythroblasts (immature cells), a large portion of the circulating volume is compromised and the infant is born with severe anemia, compensatory erythropoiesis, severe hyperbilirubinemia, and congestive heart failure.
1. Exchange transfusion on CPB, is the treatment of choice for these infant with Erythroblastosis Fetalis.
2. After cooling the patient to 17-20C, circulatory arrest is instituted.
3. The arterial line is clamped.
4. Instead of draining the venous blood into the reservoir, the infant’s blood is allowed to drain into a separate bag off of the venous line.
5. The remaining contents of the venous reservoir used during the cooling phase should also be discarded at this time.
6. A separate reservoir should be prepared in advance, and should contain enough volume to exchange transfuse the blood volume of the child 1.5 times.
7. The solution should contain RBC’s, FFP, Albumin, and balanced electrolyte solution.
8. Remember, the patient is at 17-20C and the % HCT, of the reservoir volume to be used in the exchange, should not be higher than 20% at this time.
9. After removal of the blood, the exchange transfusion is completed by opening the arterial line and slowly infusing a volume approximately equal to 1/2 of the infant’s blood volume while continuing to drain into the “separate waste reservoir”.
10. Clamp off the waste reservoir and open the venous line to the standard CPB reservoir.
11. Continue infusing the exchange volume as needed to fill the circulation and maintain CPB.
12. Rewarm as per site protocol.
13. Hemoconcentration should be performed during the rewarm to remove excess crystalloid volume and PRBC’s should be infused.
14. Prior to weaning from CPB, a full set of laboratory values should be obtained. These should include the following as a minimum:
e. Chem 7
15. Be sure ionized calcium, magnesium, potassium, and pH are corrected to normal prior to termination of CPB.
16. Additional blood products including platelets should be on hand to aid in the control of any coagulopathy which remains post CPB.