Approach to a fever (0-60 days): Clinical sciences

Fever in infants 60 days of age and younger is defined as a body temperature of 38 degrees Celsius, or 100.4 degrees Fahrenheit, or higher. Infants in this age group have a higher risk of invasive bacterial infection, when compared with older infants, so it’s important to promptly identify and treat the source of a fever. Young infants can be stratified by age and initial lab findings in order to guide the subsequent diagnostic workup and determine the need for treatment.

If a patient 60 days of age or younger presents with a fever, you should first perform an ABCDE assessment. If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access, and consider starting IV fluids. Begin continuous vital sign monitoring, including blood pressure, heart rate, and oxygen saturation, and provide supplemental oxygen if needed.

Okay, now let’s go back to the ABCDE assessment and look at stable patients. First, obtain a focused history and physical exam, and make sure to ask about exposure to sick individuals. Febrile infants often have vague symptoms, like fussiness, lethargy, and poor oral intake. Occasionally, caregivers might report symptoms that suggest a focus of infection, such as diarrhea, vomiting, cough, nasal congestion, or rash. Be sure to ask about perinatal and birth history.

The physical exam will confirm a temperature of 38 degrees Celsius or higher, frequently with an elevated heart rate. Next, you might notice signs of respiratory distress, like nasal flaring, grunting, or retractions, as well as abnormal lung sounds, like crackles and wheezing. Finally, the abdomen exam might reveal distention or tenderness. The presence of a fever, with or without other findings, in an infant 60 days or younger, should make you suspect infection.

To search for a focus of infection, order basic labs, including a CBC, inflammatory markers such as CRP and procalcitonin, and a blood culture. In addition, send urine obtained by suprapubic aspiration or catheterization for urinalysis, and reserve a sample of urine to send for culture if needed.

Now that you’ve ordered initial labs, your next step is to assess your patient’s age in order to determine how to proceed with the diagnostic workup.

First, let’s discuss febrile infants under 8 days of age. For these patients, you’ll need to perform a full evaluation for sepsis, including urine and CSF cultures. Next, hospitalize your patient, and start empiric parenteral antibiotics such as ampicillin in combination with gentamicin or cefotaxime. Additional diagnostic evaluation requires careful consideration of the perinatal history and other individual factors.