What is the appropriate workup for a fussy 2-day-old infant?

Workup for a Fussy 2-Day-Old Infant

A fussy 2-day-old infant requires a focused clinical assessment prioritizing vital signs, feeding adequacy, and identification of serious illness indicators, with laboratory workup reserved for infants with specific concerning features rather than routine testing for all fussy newborns. 1

Initial Clinical Assessment

The evaluation should focus on identifying signs that predict severe illness in this age group:

Critical Warning Signs (0-6 Days Old)

The following findings mandate immediate further evaluation and potential hospitalization 2:

• History of difficulty feeding (strongest predictor, OR 10.0) 2
• History of convulsions (OR 15.4) 2
• Lethargy or movement only when stimulated (OR 6.9) 2
• Respiratory rate ≥60 breaths per minute (OR 2.7) 2
• Severe chest indrawing (OR 8.9) 2
• Temperature ≥37.5°C or <35.5°C (OR 3.4 and 9.2 respectively) 2
• Prolonged capillary refill (OR 10.5) 2

Physical Examination Components

Perform a systematic head-to-toe examination focusing on 1:

• Skin assessment: color, perfusion, jaundice, rashes, or lesions 1
• Fontanelles and head shape: assess for bulging or abnormalities 1
• Cardiovascular: heart rate, rhythm, murmurs, and perfusion status 1
• Respiratory: rate, pattern, work of breathing, lung sounds 1
• Abdominal: organomegaly, masses, tenderness, distention (consider pyloric atresia if bilious vomiting) 3
• Umbilical site: healing status and signs of infection 1
• Neurological: tone, posture, primitive reflexes, spontaneous movements 1

Risk Stratification and Laboratory Workup

Well-Appearing Infants Without Warning Signs

Minimal or no laboratory testing is appropriate for well-appearing 2-day-old infants with normal examination findings and no specific warning signs 4. These infants are unlikely to have conditions requiring intervention and should receive close clinical follow-up rather than extensive testing 4.

Infants With Fever (Temperature ≥38°C)

If the 2-day-old has documented fever, proceed with full sepsis evaluation 3:

Laboratory workup includes 3:

• Urinalysis and urine culture (obtained by catheterization or suprapubic aspiration, never bag specimen) 3
• Blood culture 3
• Complete blood count 3
• Cerebrospinal fluid analysis (cell count, glucose, protein, Gram stain, culture) 3

Empiric antimicrobial therapy for febrile 8-21 day old infants 3:

• Ampicillin IV/IM 150 mg/kg/day divided every 8 hours PLUS
• Either ceftazidime IV/IM 150 mg/kg/day divided every 8 hours OR gentamicin IV/IM 4 mg/kg every 24 hours 3

If bacterial meningitis is suspected, increase ampicillin to 300 mg/kg/day divided every 6 hours 3.

Infants With Specific Concerning Features

For lethargy or poor feeding with abnormal vital signs or examination 4:

• Consider hematologic disorders (most common, 6.6% of cases): check bilirubin if jaundiced 4
• Assess hydration status: if dehydrated (2.9% of cases), check electrolytes 4
• If ill-appearing: perform full sepsis workup as above 4, 2

For excessive vomiting or feeding difficulties 5:

• Assess feeding technique and maternal-infant interaction 6, 5
• Evaluate for anatomical issues (tongue-tie, palate abnormalities) 1, 6
• Consider gastroesophageal reflux only after ruling out serious causes 5
• Check for pyloric atresia if bilious vomiting or abdominal distention 3

Management and Follow-Up

Hospitalization Criteria

Admit infants with any of the following 3:

• Any of the seven critical warning signs listed above 2
• Documented fever requiring empiric antibiotics 3
• Inability to feed adequately 3
• Abnormal laboratory results 3
• Parental inability to provide close monitoring 3

Outpatient Management

For well-appearing infants without warning signs 3:

• Provide verbal and written instructions for monitoring 3
• Schedule follow-up within 24 hours 3
• Ensure parents can recognize warning signs and access emergency care 3
• Phone contact should be attempted within 24 hours 3

Common Pitfalls

Avoid these errors 4, 2:

• Do not perform extensive laboratory testing on well-appearing infants with normal examinations—76% of conditions requiring intervention are clinically evident 4
• Never use bag-collected urine specimens for culture; they have unacceptably high false-positive rates 3
• Do not dismiss parental concern about feeding difficulties—this is the strongest predictor of severe illness in this age group 2
• Do not attribute all fussiness to colic or reflux without first excluding serious bacterial infection 5, 2
• Remember that a normal appearance does not completely rule out serious bacterial infection, but makes it significantly less likely 4, 2