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

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Introduction0:00–0:39

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.

Unstable patient0:39–1:07

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.

Stable patient1:07–2:10

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.

Stable fever - Labs2:10–2:31

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.

Assess age 2:31–2:42

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.

Age < 8 days2:42–3:24

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. Here’s a clinical pearl to remember!
Don’t delay initiation of antibiotics to get a lumbar puncture for CSF cultures.Now, let’s focus on the evaluation of infants between 8 and 21 days of age.

Age 8-21 days3:24–4:23

First, you'll need to send urine for culture, perform a lumbar puncture, and send CSF for analysis, which includes gram stain and culture, cell count, and protein and glucose levels.
Don’t forget to consider HSV infection, so assess your patient's risk factors, which include maternal fever or genital lesions during the perinatal period.
Additionally, be on the lookout for signs of HSV infection, such as mucous membrane ulcers, skin vesicles, seizures, or hypothermia.
If you identify any of these risk factors, order HSV testing as well. Next, admit your patient to the hospital, and start empiric parenteral antibiotics such as ampicillin in combination with gentamicin or cefotaxime, as well as IV acyclovir if you are suspecting an HSV infection.Finally, let’s turn our attention to infants between the ages of 22 and 60 days.

Age 22-60 days4:23–4:47

For this age group, you’ll need to assess the inflammatory markers and urinalysis to guide additional decision-making. Urinalysis is abnormal if the leukocyte esterase is positive, or if there are more than 5 WBCs per high power field in a centrifuged sample.Let’s first consider what to do if either the CRP or procalcitonin is abnormal, regardless of urinalysis results.

Abnormal IMs, +/- abnormal UA4:47–5:37

In this case, you should order urine cultures only if the urinalysis is abnormal, otherwise, you should primarily focus on CSF analysis.
More specifically, if your patient is 22 to 28 days old and has abnormal inflammatory markers, you should always perform a lumbar puncture and order a CSF analysis and culture.
On the other hand, if your patient is 29 to 60 days old and has abnormal inflammatory markers, you should consider ordering CSF analysis and culture after weighing the risks and benefits.
Next, admit your patient to the hospital and begin empiric parenteral antibiotics, while you are waiting for culture results.On the other hand, if the CRP and procalcitonin are normal, but the urinalysis is abnormal, you should first order a urine culture.

Normal IMs, abnormal UA5:37–7:00

Next, apply clinical judgment and shared decision-making with the patient’s caregiver, to determine whether to obtain CSF analysis and culture.
Regardless of whether you decide to perform a lumbar puncture, administer parenteral antibiotics to all febrile infants 22 to 28 days of age, and admit them to the hospital, pending culture results.
For febrile infants 29 to 60 days of age with normal inflammatory markers and abnormal urinalysis, use shared decision-making to decide whether to hospitalize your patient and treat with empiric parenteral antibiotics; or discharge your patient home with oral antibiotics and follow-up within 24 hours.
Now here’s a clinical pearl to keep in mind! Some well-appearing febrile infants with normal inflammatory markers and normal CSF without pleocytosis can be observed carefully at home, as long as the caregiver has reliable methods of communication and transportation, and they are able to return for follow-up within 24 hours.
Whenever there are 2 or more potential options for testing or management, decision-making should be a shared process between caregiver and provider, after discussing risks and benefits of testing and treatment.
Finally, if a febrile infant between 22 and 60 days old has normal inflammatory markers and urinalysis, you do not need to order a urine culture.

Normal IMs, normal UA7:00–7:48

However, if your patient is 22 to 28 days of age, using shared decision-making, you could consider performing a lumbar puncture and sending CSF for analysis and culture.
Next, admit them to the hospital and begin empiric parenteral antibiotics, pending culture results. For infants 29 to 60 days of age with normal inflammatory markers and normal urinalysis, use shared decision-making when deciding whether to admit the patient to the hospital or discharge them with close observation and follow-up within 24 hours.Alright, now it’s time to review the information you’ve gathered and carefully assess for an underlying cause.

Assess underlying cause 7:48–8:01

The history and physical exam, as well as laboratory findings, can help you identify the source of infection.First, if a febrile infant presents with nonspecific physical exam findings, and the labs reveal an elevated WBC count, elevated CRP or procalcitonin, and positive blood cultures, you can diagnose bacteremia.On the flip side, if urinalysis is positive for WBCs and leukocyte esterase, and the urine culture grows greater than 50,000 colony-forming units per milliliter, with or without a positive blood culture, diagnose UTI.Next, CNS infections should be on your radar, especially if your patient has an increased WBC count, with elevated procalcitonin and CRP, as well as CSF pleocytosis.

Bacteremia8:01–8:18

UTI8:18–8:37

CNS infections8:37–9:27

With these findings, consider meningitis or encephalitis, and if your patient has risk factors for HSV, also send CSF for a multiplex meningoencephalitis PCR.
If the PCR identifies a virus such as HSV or enterovirus, and the CSF culture is negative, you can diagnose viral meningitis or encephalitis.
On the other hand, if the PCR is negative and the CSF culture grows bacteria, diagnose bacterial meningitis. Moving on to respiratory infections!
If your patient has nasal congestion, cough, or any known sick contacts, and the physical exam reveals tachypnea, retractions, crackles, or wheezing, consider respiratory infection.

Respiratory infections9:27–10:23

In this case, order a multiplex respiratory viral panel and chest X-ray. If there’s an infiltrate or consolidation, you can diagnose pneumonia.
However, if the chest X-ray reveals hyperinflation and peribronchial thickening without an infiltrate or consolidation, with possible identification of a virus on a respiratory panel, you can diagnose bronchiolitis.
Finally, if the chest X-ray is normal, and the respiratory panel does or doesn’t identify a virus, you can diagnose a viral upper respiratory infection.
Now, if your patient presents with diarrhea, consider gastroenteritis, so be sure to send a stool sample for culture and order a multiplex gastrointestinal viral PCR.

Gastroenteritis10:23–11:00

If the culture isolates a bacterial pathogen, or if PCR identifies a virus such as rotavirus, diagnose infectious gastroenteritis.Here’s a clinical pearl!
In the first 2 weeks of life, breastfed babies may have up to 12 bowel movements per day, so to determine if the patient has diarrhea, be sure to ask if stool frequency is above baseline.Finally, if a febrile infant presents with no localizing signs or symptoms, and blood, urine and CSF cultures are negative, diagnose fever without an identifiable focus.Alright, as a quick recap… All febrile infants 60 days old or younger should have screening labs, including CBC, CRP, PCT, blood culture, and urinalysis.

Fever without an identifiable focus11:00–11:15

Review11:15–12:35

For infants 21 days old and younger, also order a urine culture, plus CSF analysis, consider HSV testing and admit to the hospital for empiric parenteral antibiotics.
For infants between 22 and 60 days of age, assess inflammatory markers and urinalysis. If they’re abnormal, or normal in patients between 22 and 28 days, order CSF analysis and culture, hospitalize your patient, and start empiric parenteral antibiotics.
If inflammatory markers are normal and urinalysis is abnormal, send urine culture, begin antibiotics, and use shared decision making to determine whether hospitalization is needed.
If inflammatory markers are normal and the baby is over 28 days old, or if CSF reveals no pleocytosis, after assessing the risks and benefits, use shared decision-making to determine further testing and treatment.
Next, assess for an underlying cause, including bacteremia, UTI, CNS or respiratory infection, and gastroenteritis. Finally, if there’s no focal signs of infection,