13.3 Hyperbilirubinemia

13.3 Hyperbilirubinemia

Quick Answer: Newborns have a high red-cell turnover, immature UDP-glucuronosyltransferase (UGT1A1), and enterohepatic recirculation, so unconjugated bilirubin rises. Screen with TcB; treat and follow with TSB. AAP 2022 phototherapy and exchange decisions are hour-specific and gestation-specific, with lower thresholds when neurotoxicity risk factors are present. AACN Certification Corporation does not publish those graphs as an official CCRN nomogram—use the current AAP figures and your unit protocol, and do not invent a fake milligram-per-deciliter table as “the AACN numbers.” A positive DAT supports isoimmune hemolysis (chapter 7). Conjugated hyperbilirubinemia is cholestasis, not physiologic jaundice. Kernicterus is permanent bilirubin injury to basal ganglia and brainstem nuclei. Intensive phototherapy is high-irradiance blue light and exposed skin with eye shields; fiberoptic devices are usually lower-irradiance adjuncts. Hydrate with milk, not extra water.

Hyperbilirubinemia is Multisystem problem MU-8. Hemolytic disease of the newborn owns DAT, Rh, ABO, IVIG, and exchange as hemolysis tools in chapter 7. This section owns the pigment: production, conjugation, screening, phototherapy physics, neurologic risk, and conjugated versus unconjugated branching. OpenExamPrep independent study material covers the patient problem as listed on the current Neonatal CCRN Test Plan. It is not a substitute for plotting the infant on the actual AAP 2022 figure hanging in your nursery.

Physiology you can teach in one minute

Senescent red cells release heme. Heme oxygenase and biliverdin reductase produce unconjugated (indirect) bilirubin, which is fat-soluble and neurotoxic if unbound. Albumin carries it to the liver. Hepatocytes conjugate it via UGT1A1 to water-soluble conjugated (direct) bilirubin, which goes into bile and stool. In the gut, beta-glucuronidase can deconjugate pigment, and it is reabsorbed (enterohepatic circulation). Anything that increases production (hemolysis, polycythemia, swallowed blood, cephalohematoma), decreases conjugation (prematurity, Gilbert/Crigler-Najjar spectrum, hypothyroidism, hypoxia), displaces albumin binding (acidosis, some drugs), or increases recirculation (delayed stooling, exclusive breastfeeding with poor intake, bowel obstruction) raises the unconjugated pool.

Physiologic jaundice is common after 24 hours in a well infant with a modest rise and a good course. Pathologic clues: jaundice in the first 24 hours, rapidly rising TSB, hemolysis, a sibling who needed exchange, family G6PD, prematurity, sepsis, or a conjugated fraction that is not “a little direct.” Breastfeeding jaundice (inadequate intake, dehydration, delayed stool) is different from breast-milk jaundice (a later, prolonged unconjugated rise in a thriving infant). Neither label is a reason to ignore a high TSB.

TcB and TSB

Transcutaneous bilirubin (TcB) is a screening estimate. It is useful for well-baby pathways and for deciding who needs a serum level. It is less reliable at higher values, after phototherapy has begun (bleached skin fools the meter), and in some skin-pigment and device combinations. Total serum bilirubin (TSB) is the treatment number. When you are near a threshold, when phototherapy is on, when hemolysis is in play, or when the infant is preterm or ill, draw TSB. Direct (conjugated) fraction matters when cholestasis is possible; a “total only” stick does not answer a 3-week-old with pale stools.

Plot the value against age in hours, not “day of life 2.” A TSB of 14 mg/dL at 18 hours is a different emergency from 14 mg/dL at 96 hours.

AAP 2022 principles—without a fake AACN nomogram

The American Academy of Pediatrics 2022 clinical practice guideline revision for infants 35 or more weeks of gestation replaced the 2004 hour-specific approach with new phototherapy and escalation-of-care / exchange graphs. Broadly, many phototherapy thresholds are higher than 2004, which is a safety and overtreatment conversation in nurseries, not a reason to withhold treatment from a rising hemolytic infant. Thresholds are lower when neurotoxicity risk factors are present. Commonly listed factors include isoimmune hemolytic disease, G6PD deficiency, asphyxia, lethargy, temperature instability, sepsis, acidosis, and albumin below about 3.0 g/dL. Gestational age itself is built into the graphs (a 35-week infant is not plotted as if term).

Escalation of care in AAP 2022 language is the zone approaching exchange, often discussed as about 2 mg/dL below the exchange threshold, where intensive phototherapy, hydration, and preparation for exchange happen now. Exchange transfusion remains the intervention when TSB is at or above the exchange graph despite intensive phototherapy, or when acute bilirubin encephalopathy is present even if the number has not “caught up.”

Infants under 35 weeks are not the 2022 term/late-preterm figure. Units use separate expert guidance and local curves. Do not import a 40-week number onto a 28-week infant.

What you must not do on this exam: invent a table of fake milligram-per-deciliter cutoffs and label it AACN official. The Neonatal CCRN Test Plan names hyperbilirubinemia as a patient problem. It does not reprint AAP figures. Independent OpenExamPrep teaching describes AAP 2022 principles (hour of life, gestation, risk factors, intensive phototherapy, exchange for dangerous unconjugated levels or encephalopathy). Your unit protocol is the bedside law.

DAT and hemolysis

The direct antiglobulin test (DAT, direct Coombs) detects antibody or complement on the infant’s red cells. A positive DAT supports isoimmune hemolytic disease (ABO, Rh, or other minor antibodies). Pair it with blood types, a reticulocyte count, a hemoglobin/hematocrit, a smear, and the rate of TSB rise. Chapter 7 taught Rh versus ABO patterns and IVIG as an adjunct to reduce hemolysis. This section’s job is: positive DAT plus a fast-rising unconjugated bilirubin is not “physiologic,” phototherapy must be intensive, and exchange plus IVIG enter the conversation sooner.

A negative DAT does not exclude hemolysis. G6PD, hereditary spherocytosis, and other intrinsic red-cell disorders can destroy cells without antibody on the membrane. Ethnicity, family history, a high reticulocyte count, and a bilirubin that outruns phototherapy still count.

Conjugated versus unconjugated

Definitions of a “high” direct fraction vary (for example, a direct bilirubin above about 1.0–2.0 mg/dL or more than about 20% of total, depending on the lab and the guideline you are using). AACN does not pick the percentage. The clinical rule is: a predominantly conjugated picture is not physiologic jaundice of the second day of life.

Kernicterus and acute bilirubin encephalopathy

Bilirubin-induced neurologic dysfunction (BIND) is the spectrum. Acute bilirubin encephalopathy can begin with lethargy, hypotonia, and a poor suck, then progress to hypertonia, retrocollis, opisthotonos, a high-pitched cry, fever, and seizures. That progression is an exchange conversation, not a “increase lights in the morning” conversation. Chronic kernicterus is permanent injury: choreoathetoid cerebral palsy, upward-gaze palsy, sensorineural hearing loss / auditory neuropathy, and dental enamel dysplasia. Prematurity, hemolysis, hypoalbuminemia, and acidosis lower the threshold at which unbound bilirubin crosses a vulnerable blood-brain barrier. Prevention is timely TSB, intensive phototherapy, IVIG when isoimmune hemolysis is driving the rise, and exchange when indicated—not withholding milk to “let the jaundice declare.”

Intensive versus fiberoptic phototherapy, eyes, and milk

Phototherapy converts unconjugated bilirubin in the skin to lumirubin and other isomers that can be excreted without conjugation. Efficacy depends on wavelength (blue-green, often discussed around 460–490 nm), irradiance, surface area, and distance from the source.

Intensive phototherapy means high spectral irradiance—commonly taught as at least 30 μW/cm²/nm in the relevant band—using LED banks or equivalent, maximizing exposed skin (diaper as small as safety allows), and often a second source (overhead plus undersource). Measure irradiance with a meter; do not assume a decorative blue glow is intensive.

Fiberoptic blankets and pads deliver lower irradiance to a smaller area. They are useful as adjuncts, during transport, or for mild elevations in well infants. They are not a substitute for intensive overhead (plus extra surface) therapy when TSB is near escalation. Combining a high-intensity bank with a fiberoptic pad can be part of an intensive setup; the blanket alone usually is not.

Eye protection is mandatory while overhead lights are on. Check that shields have not slipped and that they are not occluding the nares. Remove shields periodically for bonding and eye checks per protocol. Monitor temperature: lights can overheat, and undressing can cool an ELBW infant (section 13.2). Phototherapy increases IWL; do not treat that with bottles of free water. Feed milk (or IV dextrose-containing fluids if the infant cannot feed) to maintain hydration and stooling, which interrupts enterohepatic recirculation. Extra water does not conjugate bilirubin and can cause hyponatremia (section 13.1).

Turn the infant, watch for bronze-baby syndrome if conjugated bilirubin is high, and expect a rebound TSB after lights stop—especially with hemolysis. Re-plot. Follow hearing screening in infants who had severe hyperbilirubinemia.

Worked scenario: a 36-week infant at 20 hours of life is jaundiced, DAT-positive, TSB already near the AAP 2022 phototherapy line for a 36-week infant with isoimmune risk. This is intensive phototherapy, hydration with milk, a hematocrit and reticulocyte count, IVIG discussion, and a plotted trajectory—not a fiberoptic wrap in a bassinet and a TcB in the morning.

Exam traps: treating TcB as the treatment number after lights start; quoting a fake AACN nomogram; phototherapy as treatment of biliary atresia; missing G6PD because the DAT is negative; calling a fiberoptic pad “intensive”; skipping eye shields; giving free water; and waiting out opisthotonos. Practice: /practice/ccrn-neonatal.