Anemia of Prematurity - Portal Neonatal

department and must be heavily sedated for the procedure. The subtle abnormalities often
present in the neonatal period are not well visualized by CT scanning, and false-negative
findings are not uncommon.
• MRI: Previously, the neuronal damage characteristic of kernicterus was thought to only be
identifiable on histologic examination postmortem. However, experience has revealed that
MRI can be used to depict characteristic bilateral symmetric high-intensity signals in the
globus pallidus on both T1- and T2-weighted images in patients surviving with chronic bilirubin
encephalopathy (see Image 4). The usefulness and cost-effectiveness of this modality in the
diagnosis of more subtle forms of bilirubin toxicity remains to be fully elucidated.
Other Tests:
• Brainstem auditory evoked response (BAER): Hearing impediment is the most common
sequela of bilirubin toxicity. Impairment may be subtle and may not be clinically apparent until
the baby manifests delayed language acquisition. To maximize the baby's long-term
neurologic functioning, early identification of any degree of hearing loss is important so that
early developmental assessment and intervention can be initiated in a timely fashion. Serial
assessments of hearing function may be necessary.
Histologic Findings: On macroscopic examinations, characteristic yellow staining can be readily
observed in fresh or frozen sections of the brain obtained within 7-10 days after the initial bilirubin
insult. The regions most commonly involved include the basal ganglia, particularly the globus pallidus
and subthalamic nucleus; the hippocampus; the substantia nigra; cranial nerve nuclei, including the
oculomotor, cochlear, and facial nerve nuclei; other brainstem nuclei, including the reticular formation
and the inferior olivary nuclei; cerebellar nuclei, particularly the dentate; and the anterior horn cells of
the spinal cord.
Neuronal necrosis occurs later and results in the clinical findings consistent with chronic bilirubin
encephalopathy. Histologically, this appears as cytoplasmic vacuolation, loss of Nissl substance,
increased nuclear density with haziness to the nuclear membrane, and pyknotic nuclei (see Image 5).
TREATMENT Section 6 of 11
Medical Care: The cornerstone of management of hyperbilirubinemia is prevention of neurotoxicity.
The definitive method of removing bilirubin from the blood is via exchange transfusion. This is currently
the indicated approach in the presence of clinical bilirubin encephalopathy when the bilirubin level has
reached dangerous levels despite preventive efforts. Phototherapy is the most common method aimed
at prevention of bilirubin toxicity. Current clinical research is evaluating the use of metalloporphyrins to
block bilirubin formation by competing with the enzyme heme oxygenase.
• Exchange transfusion: This definitive therapy is used to mechanically remove already-formed
bilirubin from the blood. It is indicated whenever clinical signs of acute bilirubin
encephalopathy exist in patients who present with critically high serum bilirubin (eg, >25
mg/dL) and dehydration or when the serum bilirubin level continues to rise despite attempts to
reduce it. In the presence of Rh isoimmunization, a cord bilirubin level greater than 5 mg/dL or
a rate of rise in serum bilirubin greater than 0.5-1 mg/dL/h has been shown to be predictive of
the ultimate need for exchange transfusion. This relationship has not been demonstrated in
hyperbilirubinemia of other etiologies. This procedure is not without risk.
o Technique: The procedure involves removing the baby's native blood and replacing it with
CPD (citrate phosphate dextrose) banked blood that does not contain bilirubin. Obviously,
this must be performed gradually. Using an estimate of 80-90 cc/kg total blood volume,
usually double this amount is removed and replaced sequentially in 10-15 cc aliquots over
several hours. This approach, called a double volume exchange transfusion, harvests the
most efficient amount of bilirubin from the blood for the amount of intervention and results
in a decrease in total serum bilirubin levels by about 40%. Because of ongoing pathology