What are the bilirubin management guidelines (thresholds for phototherapy and exchange transfusion) for a newborn during the first five days, considering gestational age and risk factors?

Bilirubin Management Guidelines for Newborns in the First 5 Days

All newborns should have total serum bilirubin (TSB) or transcutaneous bilirubin (TcB) measured before discharge, with all bilirubin levels interpreted according to the infant's age in hours—not days—using hour-specific nomograms to determine phototherapy and exchange transfusion thresholds. 1, 2

Universal Screening and Initial Assessment

• Measure TSB or TcB on every jaundiced infant in the first 24 hours after birth, as jaundice appearing before 24 hours is pathologic until proven otherwise. 1, 3
• Obtain a confirmatory TSB when TcB is within 3 mg/dL of phototherapy threshold, exceeds the threshold, or is ≥15 mg/dL, as visual estimation is unreliable, particularly in darkly pigmented infants. 1, 2
• Never rely on visual assessment alone—a bilirubin level of 5 mg/dL at 10 hours is pathologic, whereas the same level at 23 hours may be normal. 1, 3

Risk Stratification Before Discharge

• Use the Bhutani nomogram to plot hour-specific bilirubin values and assign risk zones: high risk (≥95th percentile), intermediate risk (40th-95th percentile), or low risk (<40th percentile). 1
• Identify major risk factors that lower treatment thresholds: gestational age 35-37 6/7 weeks, isoimmune hemolytic disease (positive direct Coombs' test, ABO or Rh incompatibility), G6PD deficiency, sibling with neonatal jaundice requiring phototherapy, and exclusive breastfeeding with poor intake. 1, 2
• Check blood type and Coombs' test on cord blood or infant blood for all infants with ABO incompatibility (mother O, infant A or B) or Rh incompatibility. 1

Laboratory Evaluation When Jaundice is Present

• For any infant with jaundice in the first 24 hours or excessive jaundice for age, obtain: TSB, blood type (mother and infant), direct Coombs' test, complete blood count with smear, and reticulocyte count. 1
• Add G6PD testing if the infant is of Mediterranean, African, Middle Eastern, or Asian descent, or if bilirubin rises despite phototherapy or rebounds after initial decline. 1, 2, 3
• A reticulocyte count ≥6% signals active hemolysis and mandates urgent evaluation including G6PD and repeat TSB every 2-3 hours. 2
• Measure serum albumin if TSB ≥13 mg/dL; consider the bilirubin-to-albumin (B/A) ratio if albumin <3.0 g/dL, as this increases neurotoxicity risk. 1, 2

Phototherapy Thresholds (Hour-Specific)

For Term Infants ≥38 Weeks Without Risk Factors:

• At 24-48 hours of life: initiate phototherapy at approximately 12-15 mg/dL 2
• At ≥72 hours of life: initiate phototherapy at approximately 15-18 mg/dL 2

For Infants 35-37 6/7 Weeks or With Any Risk Factor:

• Thresholds are 2-3 mg/dL lower than for term infants at each time point 2
• For isoimmune hemolytic disease or G6PD deficiency: phototherapy threshold is approximately 10-12 mg/dL at 24-48 hours 2

Critical Context After Day 5:

• Beyond day 5-7, healthy term infants generally do not require phototherapy even if bilirubin exceeds conventional thresholds, because neurotoxicity risk declines sharply with postnatal age. 2
• Exceptions requiring continued vigilance: ongoing hemolysis (bilirubin rising ≥0.2 mg/dL/hour), signs of acute bilirubin encephalopathy, or TSB approaching exchange transfusion levels. 2

Intensive Phototherapy Technique

• Use blue-green LED light (430-490 nm wavelength) delivering irradiance ≥30 μW/cm²/nm over maximal body surface area. 1, 2
• Maximize skin exposure: remove the diaper when bilirubin approaches exchange levels, position light source as close as safely possible, and line the bassinet with reflective material (aluminum foil or white cloth). 1, 2
• Add a fiber-optic pad beneath the infant as an adjunct to overhead phototherapy for maximum irradiance. 2
• Continue breastfeeding or bottle-feeding every 2-3 hours during phototherapy; supplement with formula or expressed breast milk if weight loss >12% or signs of dehydration. 2

Expected Response to Phototherapy

• Normal response: TSB should decline by >2 mg/dL within 4-6 hours of initiating intensive phototherapy. 2
• For extremely high levels (TSB ≥25 mg/dL): expect a decline of 0.5-1 mg/dL per hour in the first 4-8 hours. 2
• Failure to respond (TSB not decreasing or continuing to rise despite intensive phototherapy) strongly indicates ongoing hemolysis and requires immediate escalation. 1, 2

Monitoring During Phototherapy

• For TSB ≥25 mg/dL: repeat TSB every 2-3 hours 2
• For TSB 20-25 mg/dL: repeat TSB every 3-4 hours 2
• For TSB <20 mg/dL: repeat TSB every 4-6 hours 2
• Monitor continuously for signs of acute bilirubin encephalopathy: poor feeding, marked lethargy, high-pitched cry, abnormal muscle tone (hypo- or hypertonia), opisthotonus, retrocollis, or fever. 1, 2, 4

Discontinuation of Phototherapy

• Stop phototherapy when TSB has fallen 2-4 mg/dL below the hour-specific threshold that prompted treatment initiation. 2
• For readmitted infants: discontinue when TSB falls below 13-14 mg/dL. 2

Post-Phototherapy Follow-Up

High-Risk Infants (phototherapy started <48 hours, gestational age <38 weeks, or hemolytic disease):

• Obtain TSB 8-12 hours after phototherapy cessation, followed by another measurement the next day. 2

Standard-Risk Infants:

• Obtain follow-up TSB within 1-2 days; TcB is acceptable if ≥24 hours have elapsed since phototherapy stopped. 2

• Rebound hyperbilirubinemia is uncommon but possible, especially with hemolytic disease; a rise ≥0.2 mg/dL per hour after discontinuation suggests persistent hemolysis. 2

Exchange Transfusion Thresholds

For Infants ≥38 Weeks Without Risk Factors:

• Exchange transfusion threshold: TSB ≥20-25 mg/dL depending on age in hours 4

For Infants 35-37 6/7 Weeks or With Risk Factors:

• Exchange transfusion threshold: TSB ≥18-20 mg/dL for isoimmune hemolytic disease or G6PD deficiency 4

Absolute Indications Regardless of TSB Level:

• Any signs of acute bilirubin encephalopathy (lethargy, hypotonia, poor feeding, high-pitched cry, hypertonia, opisthotonus, seizures, fever) mandate immediate exchange transfusion. 1, 4
• TSB ≥25 mg/dL is a medical emergency: admit directly to a pediatric service (not the emergency department) for immediate intensive phototherapy and preparation for exchange transfusion. 1, 4

Adjunctive Therapy for Isoimmune Hemolytic Disease:

• Administer intravenous immunoglobulin (0.5-1 g/kg over 2 hours) if TSB is rising despite intensive phototherapy or is within 2-3 mg/dL of exchange level. 1

Follow-Up Timing Based on Discharge Age

• Discharged before 24 hours: see by 72 hours 1
• Discharged between 24-47.9 hours: see by 96 hours 1
• Discharged between 48-72 hours: see by 120 hours 1
• Infants with risk factors may require two follow-up visits: first between 24-72 hours, second between 72-120 hours. 1

Critical Pitfalls to Avoid

• Do not treat 35-37 week infants as term infants—they are four times more likely to develop TSB >13 mg/dL and require lower treatment thresholds. 3
• Do not discharge 35-week infants before 48 hours without guaranteed follow-up. 1, 3
• Do not subtract direct (conjugated) bilirubin from total bilirubin when making treatment decisions, unless direct bilirubin is ≥50% of total (which requires specialist consultation). 1, 2
• Do not use homeopathic doses of phototherapy—inadequate irradiance is ineffective and delays appropriate treatment. 3
• Do not ignore prolonged jaundice beyond 2-3 weeks: measure total and direct bilirubin to rule out cholestasis, and verify normal thyroid screening. 1, 3
• Remember G6PD deficiency causes late-rising bilirubin (often after day 3-5), particularly in males of Mediterranean, Middle Eastern, African, or Asian descent. 1, 3

Special Considerations for ABO Incompatibility

• A first-day (6-hour) TSB ≥4 mg/dL has 86% sensitivity for predicting significant hyperbilirubinemia in ABO-incompatible infants. 5
• A 6-hour TSB ≥6 mg/dL has 100% sensitivity for identifying severe ABO hemolytic disease requiring intensive treatment. 5
• Predictors of severe hemolytic disease: reticulocyte count ≥6%, positive direct Coombs' test, and sibling with neonatal jaundice. 5