Neonatal Disorders

Hyperbilirubinemia

Hyperbilirubinemia:  Also known as - Neonatal Jaundice:  This disorder is the result of hemolytic processes in the neonate and brings elevated serum bilirubin levels and mild jaundice (yellowness of the skin).  It can be physiologic (with jaundice the only symptom)  it is very common and tends to more common and more severe in certain ethnic groups whose mean peak of unconjugated bilirubin is approximately twice that of the rest of the population.  It can be pathologic (resulting from an underlying disease).  Physiologic jaundice is self limiting; prognosis for pathologic jaundice varies, depending on the cause.  Untreated, severe hyperbilirubinemia may result in kernicterus, a neurologic syndrome resulting from deposition of unconjugated bilirubin in the brain cells and characterized by severe neural symptoms.  Survivors may develop cerebral palsy, epilepsy, or mental retardation, or may have only minor sequelae, such as perceptual motor handicaps and learning disorders.

Causes:  As erythrocytes break down at the end of their neonatal life cycle, hemoglobin separates into globin (protein) and heme (iron) fragments.  heme fragments form unconjugated  (indirect) bilirubin, which binds with albumin for transport to lliver cells to conjugate with glucuronide, forming direct bilirubin. Because unconjugated bilirubin is fat soluble and cannot be excreted in the urine or bile, it may escape to extravascular tissue, especially fatty tissue and the brain, resulting in hyperbilirubinemia.

This pathophysiologic process may develop several ways.  Factors that disrupt conjugation and usurp albumin-binding sites include drugs such as aspirin, tranquilizers, and sulfonamides and conditions such as hypothermia, anoxia, hypoglycemia, and hypoalbuminemia..  Decreased hepatic function can result in reduced bilirubin conjugation.  increased erythrocyte production or breakdown can accompany hemolytic disorders, or Rh or ABO incompatibility.  Biliary obstruction or hepatitis may block normal bile flow.  maternal enzymes present in breast milk can inhibit the neonate's glucuronyl transferase conjugation activity.

Symptoms:

The predominant sign of hyperbilirubinemia is jaundice, which does not become clinically apparent until serum bilirubin levels reach about 7 mg/100 ml.  Physiologic jaundice develops 24 hours after delivery in 50% of term neonates (usually day 2 - day 3) and 48 hours after delivery in 80% of premature neonates (usually 3 - 5 days).  It generally disappears by day 7 in term neonates and by day 9 or day 10 in premature neonates.  Throughout physiologic jaundice, serum unconjugated bilirubin does not exceed 12 mg/100 ml.  Pathologic jaundice may appear anytime after the first day of life and persists beyond 7 days with serum bilirubin levels greater than 12 mg/100 ml in a term neonate, 15 mg/100 ml in a premature neonate, or increasing more than 5 mg/100 ml in 24 hours.

Treatment:

Depending on the underlying cause, treatment may include phototherapy, exchange transfusions, albumin infusion, and possible drug therapy .  Phototherapy is the treatment of choice for physiologic jaundice and pathologic jaundice from erythroblastosis fetalis (after the initial exchange transfusion).  Phototherapy uses fluorescent light to decompose bilirubin in the skin by  oxidation and is usually discontinued after bilirubin levels fall below 10 mg/100 ml and continue after bilirubin levels fall below 10 mg/100 ml and continue to decrease for 24 hours.

An exchange transfusion replaces the neonate's blood with fresh blood (less than 48 hours old), removing some of the unconjugated bilirubin in serum.  Possible indications for exchange transfusions include hydrops fetalis, polycythemia, erythroblastosis fetalis, marked reticulocytosis, drug toxicity, and jaundice that develops within the first 6 hours after birth.

For excessive bilirubin levels, treatment may include albumin administration, which provides additional albumin for binding unconjugated bilirubin.  This may be done 1 to 2 hours before exchange or as a substitute for a portion of the plasma in the transfused blood.


 

Erythroblastosis Fetalis

Erythroblastosis Fetalis:   Hemolytic anemia of the fetus or newborn due to transplacental transmission of maternally formed antibody against the fetus erythrocytes, usually secondary to an incompatibility between the mother's Rh blood group and that of her offspring.
A hemolytic disease of the fetus and newborn, this disorder stems from an incompatibility of fetal and maternal blood, resulting in maternal antibody activity against fetal RBC's.

Intrauterine transfusions can save 40% of fetuses with erythroblastosis.  However, in severe, untreated erythroblastosis fetalis, prognosis is poor, especially if kernicterus (a condition with severe neural symptoms associated with high bilirubin in the blood) develops.

Causes:  Although more than 60 RBC antigens can stimulate antibody formation, erythroblastosis fetalis usually results from Rh isoimmunization - a condition that develops in approximately 7% of all pregnancies in the US.  Before the development of Rh (D) immune globulin (human), this condition was a major cause of kernicterus and neonatal death.

During her first pregnancy, an Rh-negative female becomes sensitized by exposure to Rh-positive fetal blood antigens inherited from the father. A female may also become sensitized from receiving blood transfusions with alien Rh antigens, causing agglutinins to develop; from inadequate doses of Rh(D); or from failure to receive Rh (D) after significant fetal maternal leakage from abruptio placentae.  Subsequent pregnancy with an Rh-positive fetus provokes increasing amounts of maternal agglutinating antibodies to cross the placental barrier, attach to Rh-positive cells in the fetus, and cause hemolysis and anemia.  To compensate for this, the fetus steps up the production of RBC's, and erythroblast, (immature RBC's) appear in the fetal circulation.  Extensive hemolysis results in the release of large amounts of unconjugated bilirubin, which the liver is unable to conjugate and excrete, causing hyperbilirubinemia and hemolytic anemia.

Symptoms:

Jaundice usually isn't present at birth but may appear as soon as 30 minutes later or within 24 hours.  The mildly affected neonate shows mild to moderate hepatosplenomegaly and pallor.  In severely affected neonates who survive birth, erythroblastosis fetalis usually produces pallor, edema, petechiae, hepatosplenomegaly, grunting respiration's, crackles, poor muscle tone, neurologic unresponsiveness, possible heart murmurs, a bile stained umbilical cord, and yellow or meconium stained amniotic fluid.  Untreated neonates may develop kernicterus from hemolytic disease and show signs such as anemia, lethargy, poor sucking ability, retracted head, stiff extremities, squinting, a high pitched cry, and convulsions.

Hydrops fetalis causes extreme hemolysis, fetal hypoxia, heart failure (with possible pericardial effusion and circulatory collapse), edema, peritoneal and pleural effusions, and green or brown tinged amniotic fluid (usually indication a stillbirth).

Other symptoms of the neonate with hydrops fetalis include: enlarged placenta, marked pallor, hepatosplenomegaly, cardiomegaly, and ascites.

Treatment:

Treatment depends on the degree of maternal sensitization and the effects of hemolytic disease on the fetus or neonate.

Intrauterine intraperitoneal transfusion is performed when amniotic fluid analysis suggests the fetus is severely affected, and delivery is inappropriate because of fetal immaturity.  A transabdominal puncture under fluoroscopy into the fetal peritoneal cavity allows infusion of group O, Rh-negative blood.

Planned delivery, usually 2 to 4 weeks before term date, depends on maternal history, serologic tests, and amniocentesis; labor may be induced from the 34th to 38th week of gestation.  During labor, the fetus should be monitored electronically; capillary blood scalp sampling determines acid base balance.  Any indication of fetal distress necessitates immediate cesarean delivery.

phenobarbital administered during the last 5 to 6 weeks of pregnancy may lower serum bilirubin levels in the neonate.  An exchange transfusion removes antibody coated RBC's and prevents hyperbilirubinemia through removal of the neonate's blood and replacements with fresh group O, Rh-negative blood.  Albumin infusion helps to bind bilirubin, reducing the chances of hyperbilirubinemia.  Phototherapy by exposure to ultraviolet light also reduces bilirubin levels.

Neonatal therapy for hydrops fetalis consists of maintaining ventilation by intubation, oxygenation, and mechanical assistance, when necessary; and removal of excess fluid to relieve severe ascites and respiratory distress.  Other appropriate measures include an exchange transfusion and maintenance of the neonate's body temperature.

Gamma globulin that contains anti-Rh-positive antibody (Rh (O) can provide passive immunization, which prevents maternal Rh isoimmunization in Rh-negative females.  However, it is ineffective if sensitization has already resulted from a previous pregnancy, abortion, or transfusion.

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