Anemia of Prematurity - Portal Neonatal

status (eg, watching for hypoglycemia, hypocalcemia, hyperkalemia, acidosis, hyponatremia,
renal failure) is absolutely essential to achieve a successful outcome.
• In spite of the first use of phototherapy by Cremer and associates more than 40 years ago, no
standard method for delivering phototherapy yet exists.
o Phototherapy units differ widely with respect to the type and size of lamps used. The
efficacy of phototherapy depends on the spectrum of light delivered, the blue-green
region of visible light being the most effective; irradiance (μW/cm 2 /nm); and surface
area of the infant exposed. High-intensity phototherapy first described by Tan in 1977
uses irradiance greater than 25 μW/cm 2 /nm up to 40 μW/cm 2 /nm when a doseresponse
relationship to bilirubin degradation reaches a plateau. Nonpolar bilirubin is
converted into 2 types of water-soluble photoisomers as a result of phototherapy. The
initial and most rapidly formed configurational isomer 4z, 15e bilirubin accounts for
20% of total serum bilirubin level in newborns undergoing phototherapy and is
produced maximally at conventional levels of irradiance (6-9 μW/cm 2 /nm).
o The structural isomer lumirubin is formed slowly, and its formation is irreversible and
is directly proportional to the irradiance of phototherapy on skin. Lumirubin is the
predominant isomer formed during high-intensity phototherapy. Decrease in bilirubin
is mainly the result of excretion of these photoproducts in bile and removal via stool.
In the absence of conjugation, these photoisomers can be reabsorbed by way of the
enterohepatic circulation and diminish the effectiveness of phototherapy.
Table 2. Indications for Phototherapy in the Term Infant with Hemolytic Disease of the
Newborn
Age Serum Bilirubin, g/dL
Unborn (cord blood) >3.5
10
12
14
2-3 d >15
• Exchange transfusion removes circulating bilirubin and antibody-coated RBCs, replacing them
with RBCs compatible with maternal serum and providing albumin with new bilirubin binding
sites.
o The process is time consuming and labor intensive, but it remains the ultimate
treatment to prevent kernicterus. The process involves the placement of a catheter via
the umbilical vein into the inferior vena cava and removal and replacement of 5- to 10mL
aliquots of blood sequentially, until about twice the volume of the neonate's
circulating blood volume is reached (ie, double-volume exchange).
o This process removes approximately 70-90% of fetal RBCs. The amount of bilirubin
removed varies directly with the pretransfusion bilirubin level and amount of blood
exchanged. Because most of the bilirubin is in the extravascular space, only about
25% of the total bilirubin is removed by an exchange transfusion. A rapid rebound of
serum bilirubin level is common after equilibration and frequently requires additional
exchange transfusions.
o The indications for exchange transfusion are controversial, except for the fact that
severe anemia and the presence of a rapidly worsening jaundice despite optimal
phototherapy in the first 12 hours of life indicate the need for exchange transfusion. In
addition, the presence of conditions that increase the risk of bilirubin encephalopathy
lowers the threshold of safe bilirubin levels.