When to recheck serum bilirubin levels in patients undergoing phototherapy?

Monitoring Serum Bilirubin Levels During Phototherapy

Serum bilirubin levels should be rechecked based on the initial TSB level: every 2-3 hours if TSB ≥25 mg/dL, every 3-4 hours if TSB 20-25 mg/dL, and every 4-6 hours if TSB <20 mg/dL until there is clear evidence of declining levels. 1, 2

Initial Monitoring Schedule

The frequency of serum bilirubin monitoring during phototherapy depends on several factors:

• For TSB ≥25 mg/dL (428 μmol/L):

  • Recheck TSB within 2-3 hours
  • Continue frequent monitoring until clear evidence of decline

• For TSB 20-25 mg/dL (342-428 μmol/L):

  • Recheck TSB within 3-4 hours
  • If declining, subsequent checks can be spaced to 4-6 hours

• For TSB <20 mg/dL (342 μmol/L):

  • Recheck TSB in 4-6 hours
  • If continuing to fall, subsequent checks can be done every 8-12 hours 1

Expected Response to Phototherapy

Understanding the expected response helps determine monitoring frequency:

• With intensive phototherapy, expect a decline of 30-40% in the initial bilirubin level within 24 hours 1
• The most significant decline occurs in the first 4-6 hours 1
• Effective phototherapy should produce a decline of >2 mg/dL within the first 4-6 hours 2
• With standard phototherapy systems, expect a decrease of 6-20% of the initial level in the first 24 hours 1

Special Considerations

• Extremely high bilirubin levels (>30 mg/dL): A decline of up to 10 mg/dL can occur within a few hours, with a decrease of at least 0.5-1 mg/dL per hour expected in the first 4-8 hours 1

• Infants with hemolytic disease: These infants may have a less predictable response and require more frequent monitoring 1

• Infants requiring escalation of care: TSB should be measured at least every 2 hours from the start of the escalation of care period until the escalation of care period ends 1

When to Discontinue Phototherapy

• Phototherapy may be discontinued when the TSB has declined by 2-4 mg/dL below the hour-specific threshold at which phototherapy was initiated 1, 2

• For infants readmitted after birth hospitalization (usually for TSB levels ≥18 mg/dL), phototherapy may be discontinued when serum bilirubin falls below 13-14 mg/dL 1

Post-Phototherapy Monitoring

After discontinuing phototherapy, follow-up TSB measurements are essential:

• High-risk infants (received phototherapy <48 hours of age, gestational age <38 weeks, positive DAT, or suspected hemolytic disease): Check TSB 8-12 hours after discontinuation and again the following day 1

• Other infants: Check TSB within 1-2 days after discontinuation 1

• If phototherapy was used for hemolytic disease or initiated early and discontinued before the infant is 3-4 days old, a follow-up bilirubin measurement within 24 hours after discharge is recommended 1

Common Pitfalls to Avoid

1. Inadequate monitoring frequency: Failing to monitor frequently enough in cases of severe hyperbilirubinemia can miss rapid rises in bilirubin levels

2. Premature discontinuation: Stopping phototherapy too early can lead to rebound hyperbilirubinemia

3. Relying on transcutaneous bilirubin (TcB) during phototherapy: TcB measurements are not accurate enough for treatment decisions during phototherapy unless measured on patched skin areas 1, 3

4. Failing to identify underlying causes: Not evaluating the cause of hyperbilirubinemia in infants requiring phototherapy, particularly when response to therapy is suboptimal 1

5. Missing signs of acute bilirubin encephalopathy: Failing to recognize signs that would necessitate immediate exchange transfusion regardless of TSB trends 1

By following these evidence-based monitoring protocols, clinicians can effectively manage hyperbilirubinemia while minimizing unnecessary blood draws and optimizing patient outcomes.