|
Objectives
What
is the Problem?
Definition of Terms
Production,
Metabolism, Transport and Excretion
Assessment
Practice
Standard
Current
Treatment
Education
Bibliography
Quiz
Main
Lab Page
|
Definition
of Terms
- Bilirubin
- is the product of the breakdown
of heme, most of which is found in red blood cells (RBC's).
- Hyperbilirubinemia
- refers to bilirubin levels
that have exceeded a specified level or rate of rise that, unchecked,
might lead to bilirubin encephalopathy or kernicterus. The specified
level considered to be clinically significant varies depending on the
gestational age and other conditions or diseases of the neonate.
- Jaundice
- is characterized by hyperbilirubinemia
and deposition of bile pigment in the skin, mucous membranes and sclera
resulting in yellow appearance of the patient's skin.
- Physiologic Jaundice
- is a normal process seen
in 45-60% of term infants and up to 80% of preterm newborns within the
first week after birth. It occurs during the first few days after birth
(usually associated with a bilirubin level > 5-7mg/dl) and is due
to normal physiologic processes. Most often the process is self-limiting,
resolves by the end of the first week of life and requires no treatment.
Cord bilirubin levels are generally < 2mg/dl in physiologic jaundice.
-
- Pathologic Jaundice
- refers to jaundice that
arises from pathologic factors such as blood group incompatibility,
sepsis or excessive bruising, that alter the usual processes involved
in bilirubin metabolism. It frequently but not always appears in the
first 24 hours of life and/or the serum bilirubin level rises at a rate
of more than 5mg/dl per day, persisting beyond the usual age for disappearance
in term or preterm infants. Conditions that alter the production, transport,
uptake, metabolism, excretion or reabsorption of bilirubin may lead
to pathologic jaundice. These alterered conditions may lead to excessive
unconjugated bilirubin. Untreated, the rise may reach a toxic level,
resutling in kernicterus.
-
- Breastfeeding Jaunice
- (early onset) appears in
the first days of life of breastfed newborns and is at least partly
related to early ineffective breastfeeding practices. Ineffective breastfeeding
potentially decreases volume and caloric intake and may lead to dehydration
and delayed passage of meconium. This delayed stooling allows enterohepatic
circulation reuptake of bilirubin and an increase in the serum level
of unconjugated bilirubin. Early and frequent breastfeeding without
water or other fluids is recommended to ensure adequate volume of colostrum
and milk.
- Breast Milk Jaundice
- (late onset) occurs after
3 to 5 days of life with a steady increase in serum bilirubin that usually
peaks at 5-10mg/dl at about two weeks of age. It appears to be related
to change in the composition or physical structure of milk that results
in enhanced enterohepatic circulation.
Stopping breastfeeding
isn't recommended for most newborns with breastmilk jaundice. Interrupting
breastfeeding may be a management strategy for those individual
newborns whose serum bilirubin concentrations approach levels considered
dangerous for the development of kernicterus. (AAP Provisional Committee
for Quality Improvement and Subcommitte on Hyperbilirubinemia, 1994;
Halamek & Stevenson, 1997) (Reiser, 2001).
- Indirect Bilirubin
- is also known as unconjugated
bilirubin, which has not yet been metabolized by the liver. It is of
greatest concern in newborns. It is fat soluble and cannot be easily
excreted in bile or urine. When indirect bilirubin builds up in the
blood, it can be deposited in fatty tissues such as the skin (leading
to jaundice) and brain (leading to kernicterus).
-
- Direct Bilirubin
- is also known as conjugated
bilirubin, which has been metabolized by the liver. It is water soluble
and thus readily excreted via the biliary system into the intestines.
Most direct bilirubin is removed from the body in stool.
-
- Total Serum Bilirubin
- is a combination of both
the direct and indirect bilirubin levels in the blood.
-
- Kernicterus
- involves permanent damage
related to deposition of excess bilirubin in brain tissues - particulary
those in the basil ganglia. Early signs may be absent or, with a severe
insult, include lethargy, poor feeding, temperature instability, hypotonia,
and a high-pitched cry. Long-term sequelae may include deficits in hearing
and speech as well as motor and perceptual function deficits. It may
also include more pronounced deficits such as delayed motor development,
athetoid cerebral palsy, dental dysplasia, seizures and mental retardation.
-
- Phototherapy
- is the most common therapy
used for hyperbilirbinemia to avert bilirubin toxicity. It is theorized
that photo-oxidation and photoisomerization convert indirect bilirubin
to a water soluble form that can be excreted in the urine.
-
- Rh Incompatibility
- occurs when an Rh-negative
mother produces an Rh antibody in response to the presence of the Rh
antigen on the fetal RBC membrane. An Rh-negative mother carrying an
Rh positive fetus becomes sensitized with a transplacental hemorrhage
of as little as 0.1 - 0.5 ml. In subsequent pregnancies, IgG antibodies
cross the placenta and attach to antigenic sites on fetal RBC membranes,
resulting in hemolysis.
- ABO Incompatibility
- occurs when antigens present
on the RBC surface of each blood type react with antibodies in the plasma
of opposite blood types. The hemolytic process is similar to Rh incompatibility,
but it is more common, generally milder and may occur in the first pregnancy.
It occurs almost exclusively in type-O mothers and is caused by maternal
anti-A or anti-B antibodies reacting with fetal A and B antigens on
the RBC surface. Hemolysis of fetal red blood cells can occur when the
maternal antibodies cross the placenta.
- Direct Coombs Test
- measures antibody presence
on the RBC surface.
- Indirect Coombs Test
- measures antibody in the
serum.
- Biliary Atresia
- refers to a form of obstructive
jaundice that involves the complete obstruction of bile flow resulting
from fibrosis of the extrahepatic ducts. This can interfere with the
liver's ability to excrete the direct bilirubin produced. If these carriers
become saturated because of high bilirubin levels, the liver will be
unable to excrete direct bilirubin and levels in the blood will increase,
leading to direct hyperbilirubinemia. Jaundice persists after the first
week of life and the direct bilirubin level increases gradually. The
infant's color becomes greenish-bronze, stools become pale tan from
lack of bilirubin and urine becomes dark from urobilinogen.
- Neonatal Hepatitis
- can also lead to obstructive
jaundice. The cause may be viral, a secondary manifestation of a congenital
infection or undetermined. The onset of jaundice usually occurs within
the first 4 weeks of life with progressive abdominal distention. The
infant may eat poorly and be unable to retain feedings.
-
- Exchange Transfusion
- refers to a procedure used
to remove circulating bilirubin and antibody-coated RBC's, as well as
some of the circulating maternal antibodies and replaces them with RBC's
compatible with the mother's antibody-rich serum. The transfusion also
normalizes the hematocrit and provides fresh albumin with binding sites
for bilirubin. This procedure may have to be repeated more than once
before stabilization is attained. It is not risk-free and the estimated
morbidity risk is about 5%, with mortality estimated at 0.5%.
- Glucose 6 Phosphate Dehydrogenase
Deficiency
- is a recessive trait carried
on the X chromosome. It is prevalent in African, Mediterranean and Asian
populations. G6PD deficient RBC's cannot adequately defend against oxidant
stresses leading to hemolysis. Concurrent infection is the event that
most frequently precipitates severe jaundice or hyperbilirubinemia.
|