Kernicterus is a condition characterized by deposits of heme byproduct i.
e. bilirubin in CNS leading to loss of ability to react to loud sound (moro or startle reflex) , body posture , poor eating and activity levels, hydrocephalus leading to bulging fontanelle, a high-pitched shrill cry, and seizure activity. Those who survive this condition develop hypotonia, deafness and are mentally retarded. The remaining 25 % suffer from most severe manifestation of erythroblastosis fetalis called hydrops fetalis which is characterized by high cardiac output leading to heart failure, edema, fluid accumulation in peritoneal cavity and pericardial cavity, and erythropoiesis in parts other than bone marrow.. The infants are extremely pale with hemoglobin level below 5. Nearly half of infants develop this condition before 34 weeks gestation while the remaining half after 34 weeks gestation.
Male fetuses are 13 times more likely to develop this condition. These infants die just before or after delivery and require tranfusions on immediate basis to give infant some chances of survival .Hydrops fetalis usually has a mortality rate of about 30 %.MEDICAL CARE: Anti Rh ImmunoglobulinIn 1966 a combined USA and UK based study group suggested the use of anti D immunoglobin (IgG) soon after delivery in Rh negative women to prevent sensitization. In 1971 WHO organization recommended 25 mcg of IgG intramuscular for very 1 ml of fetomaternal hemorrhage of Rh positive packed RBCs or 2 mL of whole blood.In 1998, American Association of Blood Banks and the American College of Obstetrics and Gynecologists recommended prophylactic use at 28 weeks’ gestation.
Routine prophylactic use has caused sufficient decline in cases RhD alloimmunization( reduction from 10-20 % to 1 % in US), and erythroblastosis fetalis is becoming increasingly rare.The exact mechanism of action prevention of sensitization is not known .However the most likely theory is that they work by coating the surface of fetal erythrocytes. Theses complexes of antigens and antibodies cross placental before sensitization of maternal immune system. Their short half-life requires a single dose to be given between 28-32 weeks and one dose soon after delivery.
CURRENT RECOMMENDATIONS:? If a Rh negative women has been exposed to Rh positive blood from fetus due to anti partum bleeding or feto maternal hemorrhage and has not been immunized she should receive Rh IgG. Dose: 300 mcg of Rh IgG IM/30 ml of amount of fetal blood that came in contact with maternal circulation.? If she has abortion or miscarriage in first triemester with volume of hemorrhage believed to be low than low dose options of IgG (i.e 50 mcg) are availablePRENATAL CARE:EMERGENCY CARE: It varies with patient presentation and fetus gestational age. If not sensitized Rh IgG (RhoGAM) is administered and patient referred for subsequent evaluation. If elevated level of maternal antibodies show previous sensitization patient is considered high risk and referred for special care. If the mother has not been sensitized on previous delivery with Rh positive fetus and she herself was Rh negative, then she should be administered human anti-D immune globulin (Rh IgG or RhoGAM) on immediate basis and referred for further evaluation.
TESTS:ROSETTE SCREENING TESTS:It is used to detect immune response caused by minor volume of fetomaternal hemorrhage.KLEIHAUER-BETKE TEST: Performed if there is suspicion that amount of fetomaternal hemorrhage is greater than 30 ml.It measures the amount of fetal erythrocytes in circulation and helps determne whether further dose of IgG should be given. Standard dose is 20 mcg/ml of fetal erythrocytes.Maternal titers: High level of maternal antibody titers also show that sensitization has taken place and point out the requirement for advanced testing such as amniocentesis and/or cordocentesis, to evaluate fetal health.
When titer reaches critical value of 1:32 high risk of fetal hydrops has developed and intense monitoring is required.COOMBS TEST: As a previous history of hydropic further increases the risk upto 90 % in next pregnancy such patient should undergo coombs test in first prenatal visit.Serological testing: Positive coombs test should be followed by determining of paternal blood type and particular Rh genotype involved.High-resolution ultrasonography: Used in detection of early hydrops and has resulted in reduction of fetal trauma and morbidity rate to less than 2% during intrauterine invasive procedures.Aminocentesis: As early as 5 weeks at 10-14 days interval to monitor severity of disease.Peak systolic middle cerebral artery (MCA) Doppler velocity: Detection of fetal anemia as early as 15 weeks gestation.Intraperitoneal transfusion: Volume of transfusion is determined byIPT volume = (gestation in wk – 20) X 10 mLRepeated when IPT level drops below 10 g/Dl.Direct Intravenous transfusion: More effective than IPT in hydropic fetus.
Started when hemoglobin level is less than 11g/Dl. Repeated at intervals of 10 days, 2 weeks and every three weeks. It is the only possible intervention for moribund hydropic fetuses and has a survival rate of 88 %.POST NATAL CARE:Delivery of hydropic fetus should be as non-traumatic as possible and attended by neonatologist ready to perform exchange transfusion.
The clinical symptoms depend upon severity of disease.CLINICAL PRESENTATION: ? Rapidly progressive severe hyperbilirubinemia ? Atrial Flutter? Cardiac Tumors? Cytomegalovirus Infection? Galactose-1-Phosphate Uridyltransferase Deficiency (Galactosemia)? Hypothyroidism? Parvovirus B19 Infection? Syphilis? Toxoplasmosis? Tyrosinemia? Hemolysis on blood ? Anemia? Nucleated RBCs, reticulocytosis, polychromasia, anisocytosis, spherocytes, and cell fragmentation? Neutropenia? Thrombocytopenia? Hypoglycemia ? Jaundice? Pallor, ? Hepatosplenomegaly ? Fetal hydrops LABORATORY FINDINGS: Positive coombs testMANAGEMENT:Mild hemolytic disease requires only initial phototherapy. However hemoglobin level should be monitored for late onset anemia. Moderate hemolytic disease requires early exchange transfusion with type-O Rh-negative fresh RBCs along with intensive phototherapy. However the use of Intravenous immunoglobulin therapy has greatly reduced transfusion requirements.
Mild cases of hydrops have a reversal rate of 88 % with intravenous transfusions but severe cases have a mortality rate of about 61 % despite use of IVT.Competitive heme oxygenase inhibitorTin porphyrin inhibits conversion of heme to bilirubin and is used in hyperbilirubinemia. It has been shown to reduce need for transfusion and photoEXample: Stannsoporfin (SnMP, Stanate)Stannsoporfin (SnMP, Stanate)Immunomodulator (IVIG):