What is the comprehensive management plan—including ampicillin and gentamicin dosing, supportive care, newborn screening, immunizations, and discharge criteria—for a 13‑day‑old late‑preterm infant (37 weeks + 5 days gestation) weighing approximately 3 kg (≈60th percentile) who is undergoing a septic work‑up with blood cultures?

Comprehensive Management Plan for 13-Day-Old Late-Preterm Infant with Suspected Sepsis

Antibiotic Therapy

Ampicillin plus gentamicin is the recommended empiric antibiotic regimen for this infant, providing coverage against Group B Streptococcus and gram-negative organisms including E. coli. 1, 2, 3

Dosing Regimen (assuming weight ~3 kg)

• Ampicillin: 50 mg/kg IV every 8 hours (for infants 8-28 days of age without meningitis) 1
• Gentamicin: 4-5 mg/kg IV every 24 hours (extended-interval dosing for infants >7 days and >34 weeks gestational age) 2

Key consideration: At 13 days of age, this infant falls into the 8-28 day age category where ampicillin and gentamicin remain first-line, though broader-spectrum therapy with ceftazidime may be considered if there is concern for ampicillin resistance. 1 However, avoid routine use of cefotaxime as it is associated with increased mortality compared to gentamicin (adjusted OR 1.5,95% CI 1.4-1.7) and promotes emergence of resistant organisms. 4, 5

Duration of Therapy

• If blood cultures are negative at 48 hours and infant is clinically well: Discontinue antibiotics 6
• If cultures are positive: Continue therapy for 7-10 days for bacteremia without focus, 14 days for meningitis 1
• Monitor: Obtain gentamicin trough level before 3rd dose to ensure <2 mcg/mL; monitor renal function and hearing 2

Septic Work-Up Components

Laboratory Evaluation Completed

Full diagnostic evaluation should include: 1

• Blood culture (obtained before antibiotics) 1, 2
• Complete blood count with differential and platelet count (ideally at 6-12 hours of life for initial evaluation, but at presentation for late evaluation) 1, 6
• Lumbar puncture with cerebrospinal fluid analysis if infant is stable enough to tolerate procedure and sepsis is suspected 1
• Chest radiograph if respiratory abnormalities are present 1
• Urine culture (for late-onset sepsis evaluation in infants >7 days) 1

Expected CBC Findings to Monitor

• Abnormal findings suggesting sepsis: WBC <5,000 or >25,000/mm³, absolute neutrophil count <1,500/mm³, I:T ratio >0.2, thrombocytopenia <100,000/mm³ 1, 2
• Thrombocytopenia does not contraindicate ampicillin-gentamicin use 2

Supportive Care

Monitoring Requirements

• Vital signs every 4 hours: Temperature, heart rate, respiratory rate, blood pressure 1
• Continuous cardiorespiratory monitoring for apnea, bradycardia, desaturation 1
• Daily weights and strict intake/output monitoring 1
• Serial CBCs: Repeat at 24-48 hours if initial values abnormal 1
• Blood glucose monitoring every 6-12 hours initially 1

Nutritional Support

• Continue feeding if tolerated (oral or gavage) unless signs of NEC or hemodynamic instability 1
• Target intake: 150-160 mL/kg/day by 13 days of age for term/late-preterm infants 1
• Monitor for feeding intolerance: Abdominal distension, emesis, bloody stools 1

Newborn Screening Requirements

Metabolic Screening

For a 13-day-old infant, verify completion of: 1

• Initial newborn screen (typically done 24-48 hours after birth)
• Repeat newborn screen (recommended at 1-2 weeks for late-preterm infants born at 37 5/7 weeks due to risk of false negatives from early discharge) 1
• Conditions screened: PKU, hypothyroidism, galactosemia, sickle cell disease, cystic fibrosis, and 25+ other metabolic disorders depending on state 1

Hearing Screening

• Automated auditory brainstem response (AABR) or otoacoustic emissions (OAE) should be completed before discharge 1
• Gentamicin exposure requires follow-up hearing evaluation at 6 months due to ototoxicity risk 2

Critical Congenital Heart Disease Screening

• Pulse oximetry screening should have been completed after 24 hours of age but before discharge from birth hospitalization 1
• If not done: Perform now, though sensitivity decreases with age 1

Immunization Status

Hepatitis B Vaccine

For a 13-day-old infant at 37 5/7 weeks gestation: 1

• If birth weight ≥2 kg: First dose should have been given before initial hospital discharge 1
• If not yet given: Administer first dose now (can be given during sepsis evaluation if infant is stable) 1
• Schedule: Second dose at 1-2 months, third dose at 6-18 months 1

Other Vaccines

• No other vaccines are due until 2-month visit 1
• Delay routine 2-month vaccines if infant remains hospitalized or acutely ill 1

Discharge Readiness Criteria

Clinical Stability Requirements

Infant must meet ALL of the following before discharge: 1

• Afebrile for ≥24 hours (temperature 36.5-37.5°C) without antipyretics 1
• Stable vital signs for ≥24 hours (HR 100-160, RR <60, no apnea/bradycardia) 1
• Feeding well with adequate intake (>100 mL/kg/day) and appropriate weight gain or stable weight 1
• Blood cultures negative for ≥48 hours (ideally 72 hours for late-onset sepsis) 1
• Clinical improvement: Resolution of lethargy, improved perfusion, normal activity level 1

Minimum Observation Period

• At least 48 hours of observation after initiating antibiotics, even if cultures are negative 1
• For this 13-day-old infant: If cultures remain negative and clinical course is reassuring, antibiotics can be discontinued at 48 hours and discharge considered at that time 1, 6

Laboratory Requirements Before Discharge

• Repeat CBC showing improvement or normalization of abnormal values 1
• Negative blood cultures at 48-72 hours 1
• Bilirubin level if jaundice present (late-preterm infants at higher risk) 1
• Newborn screening results reviewed and follow-up arranged for any abnormal results 1

Social and Follow-Up Requirements

Before discharge, ensure: 1

• Parent education on signs of sepsis recurrence: fever, lethargy, poor feeding, irritability, respiratory distress 1
• Car seat safety test completed (required for infants <37 weeks at birth) 1
• Follow-up appointment scheduled within 24-48 hours of discharge 1
• Primary care provider identified and notified of hospitalization 1
• Access to medical care readily available and parent able to comply with home observation instructions 1

Special Considerations for Late-Preterm Infant (37 5/7 weeks)

Increased Risk Factors

• Late-preterm infants have 3-fold higher risk of early-onset sepsis compared to term infants 1
• Higher risk of feeding difficulties, hypoglycemia, hyperbilirubinemia, and temperature instability 1
• Immature immune system increases susceptibility to infection 1

Common Pitfalls to Avoid

• Do NOT use cefotaxime routinely in place of gentamicin due to increased mortality risk and emergence of resistant organisms 4, 5
• Do NOT delay antibiotic initiation while awaiting lumbar puncture if infant is unstable 1, 2
• Do NOT discharge before 48 hours of observation even if initial cultures are negative 1
• Do NOT assume adequate intrapartum prophylaxis eliminates sepsis risk; this infant is 13 days old and at risk for late-onset sepsis from different pathogens 1
• Do NOT forget gentamicin level monitoring to prevent nephrotoxicity and ototoxicity 2

Maternal History Considerations

Review maternal records for: 1, 3, 6

• Group B Streptococcus status and adequacy of intrapartum prophylaxis (≥4 hours of penicillin, ampicillin, or cefazolin before delivery) 1
• Chorioamnionitis (maternal fever, fetal tachycardia, uterine tenderness) 1, 3, 6
• Duration of membrane rupture (≥18 hours increases risk) 1
• Maternal antibiotics received during labor 1