What is the management approach for a 5-week-old infant presenting with fever?

From the Guidelines

A 5-week-old infant with fever requires immediate medical evaluation in an emergency department, as this represents a medical emergency. The management includes a full sepsis workup with blood, urine, and cerebrospinal fluid cultures, followed by empiric antibiotic therapy, typically ampicillin (150 mg/kg per day divided every 8 hours) plus either ceftazidime (150 mg/kg per day divided every 8 hours) or gentamicin (4 mg/kg per dose every 24 hours) 1. The infant should be hospitalized for observation and treatment pending culture results, typically for 48-72 hours. Acetaminophen (10-15 mg/kg every 4-6 hours) may be used for fever control. Fever in infants under 8 weeks is considered high-risk because their immature immune systems make them vulnerable to serious bacterial infections, including meningitis, bacteremia, and urinary tract infections. Their inability to localize infections and limited ability to demonstrate specific symptoms necessitates this aggressive approach. Parents should never delay seeking medical attention or administer antibiotics at home, as prompt treatment is essential to prevent serious complications. Some key considerations in the management of febrile infants include:

• The risk of serious bacterial infections, such as urinary tract infections, bacteremia, and meningitis, is higher in younger infants 1
• The use of a local antibiogram can guide antibiotic choices 1
• The importance of obtaining a full sepsis workup, including blood, urine, and cerebrospinal fluid cultures, to guide antibiotic therapy 1
• The need for hospitalization and observation pending culture results, typically for 48-72 hours 1
• The use of acetaminophen for fever control, with dosing of 10-15 mg/kg every 4-6 hours 1

From the FDA Drug Label

It is recommended that there be at least 10 days’ treatment for any infection caused by Streptococcus pyogenes to prevent the occurrence of acute rheumatic fever Due to incompletely developed renal function affecting elimination of amoxicillin in this age group, the recommended upper dose of amoxicillin is 30 mg/kg/day divided every 12 hours. Treatment should be continued for a minimum of 48 to 72 hours beyond the time that the patient becomes asymptomatic, or evidence of bacterial eradication has been obtained.

The management approach for a 5-week-old infant presenting with fever is not directly addressed in the provided drug label, as the label provides dosage recommendations for pediatric patients aged 3 months (12 weeks) and older, and a separate recommendation for pediatric patients aged less than 12 weeks (3 months) which includes the 5-week-old age group.

• The recommended upper dose of amoxicillin for pediatric patients aged less than 12 weeks is 30 mg/kg/day divided every 12 hours 2.
• Treatment should be continued for a minimum of 48 to 72 hours beyond the time that the patient becomes asymptomatic, or evidence of bacterial eradication has been obtained 2. However, the provided label does not give specific guidance on the evaluation or initial management of fever in a 5-week-old infant.

From the Research

Management Approach for a 5-Week-Old Infant Presenting with Fever

• The American Academy of Pediatrics (AAP) guidelines published in 2021 provide recommendations for the evaluation and management of well-appearing febrile infants from age 8 to 60 days 3.
• For infants younger than one month, factors that suggest serious infection include poor arousability, petechial rash, delayed capillary refill, increased respiratory effort, and overall physician assessment 4.
• Urinary tract infections are the most common serious bacterial infection in children younger than three years, so evaluation for such infections should be performed in those with unexplained fever 4.
• Abnormal white blood cell counts have poor sensitivity for invasive bacterial infections; procalcitonin and C-reactive protein levels, when available, are more informative 4.
• When empiric treatment is appropriate, suggested antibiotics include ceftriaxone or cefotaxime for infants one to three months of age and ampicillin with gentamicin or with cefotaxime for neonates 4.

Considerations for Fever Management in Infants

• Protocols such as Step-by-Step, Laboratory Score, or the Rochester algorithms may be helpful in identifying low-risk patients 4.
• Rapid influenza testing and tests for coronavirus disease 2019 (COVID-19) may be of value when those diseases are circulating 4.
• The choice of antibiotics should reflect local patterns of microbial resistance 4.

Limitations of Current Evidence

• The AAP guidelines do not specifically address the management of fever in infants younger than 8 days 3.
• There is limited evidence on the management of fever in infants younger than 5 weeks, and more research is needed to inform clinical practice.