Fever of Unknown origin

Question 1

Fever generally is defined as a core temperature of at least

Answer 1

38.0ºC (100.4ºF)

Question 2

Fever is believed to provide an evolutionary
advantage in fighting off infection.

Answer 2

Bacteria and viruses are
heat sensitive and exhibit temperature-dependent toxin production, growth, and response to antibiotics.

Question 3

This age group is highly vulnerable to overwhelming infection

Answer 3

0-28 Days of Age. Infants in this age group can progress in a matter of hours from vigorous to moribund. For this reason, all infants under 28 days of age with temp >= 100.4 (definition of fever) are evaluated with a full ‘septic work-up.
These infants are then promptly treated with Cefotaxime and Ampicillin IV plus acyclovir pending HSV results. All of these infants are admitted

Question 4

Septic workup

Answer 4

CBC, BC, cath UA/UC, and Lumbar Puncture (LP). A CXR should be obtained if there is a cough or signs of lower respiratory tract disease. Herpes Simplex Virus PCR should be obtained if Herpes is suspected by history (maternal herpes) or a vesicular rash.

Question 5

In the otherwise healthy infant younger than three months of age, fever of concern generally is defined by rectal temperature

Answer 5

≥38.0°C (100.4°F).

Question 6

In children 3 to 36 months, fever generally is defined by rectal temperatures ranging from

Answer 6

from ≥38.0 to 39.0°C (100.4 to 102.2°F) and fever of concern by rectal temperatures ≥39.0°C (102.2°F)

Question 7

In older children and adults, fever may be defined by oral temperatures ranging from

Answer 7

from ≥37.8 to 39.4°C (100.0 to 103.0°F) and fever of concern by oral temperatures ≥39.5°C (103.1°F).

Question 8

Children are more comfortable when fever is reduced
Therefore…OVER WHAT TEMPERATURE SHOULD BE TREATED

Answer 8

fevers over 102 degrees F rectally should be treated

Question 9

Fever Myths

Answer 9

Fever “fries the brain”
The response of the fever to antipyresis is predictive of serious disease.
The duration of fever correlates with severity of disease

Question 10

A febrile seizure has the following characteristics

Answer 10

age 6mos-6yrs
< 15 minutes
Generalized
no respiratory compromise

Question 11

FEVER IN 28-60 Days of Age

Answer 11

Most of these infants will receive a full septic work-up and either IV antibiotics and admission or, if all aspects of the work-up are benign, then IM Ceftriaxone and close follow-up.
Some infants with a totally normal evaluation up to, but not including lumbar puncture, may be discharged without a lumbar puncture. However, under no circumstances may an LP be omitted if the infant is on antibiotics at presentation or if the discharge plan includes antibiotics (for OM for example).
close follow-up is important – PCP or repeat visit in ER

Question 12

Infants with an antigen-proven viral infection

Answer 12

may not need a full septic work-up if they are vigorous and a more limited work-up is benign.
close follow-up is important – PCP or repeat visit in ER

Question 13

The Hemophilus and Pneumovax vaccines have

Answer 13

dramatically reduced the incidence of Occult Bacteremia. One might think that in the 2-6 month age group the risk remains high because most of these infants are not fully immunized

Question 14

2-6 Months of Age

Answer 14

Occult Bacteremia (positive blood culture in a febrile infant who has a benign examination) has been a major concern in this age group and, in fact, in infants up to 24 months of age.
That said, Occult Bacteremia cannot be entirely ignored. There is no immunization or herd immunity protection from bacteremia secondary to meningococcus or salmonella. And Pneumovax does not protect against every strain of pneumococcus (and the strains not covered are becoming more prevalent).
Most of these infants have not received their full complement of Hemophilus and Pneumovax immunizations – a fact that has medical implications when deciding on the need to search for and possibly treat infants in this age group for Occult Bacteremia

Question 15

6-24 Months of Age

Answer 15

There are only two significant differences between this age group and the younger age group.
First, the need to pursue Occult Bacteremia lessens considerably if the infant’s Hib and Pneumovax immunizations are complete (3-4 vaccinations of each). Obtaining a CBC and blood culture is no longer routine based on the height of fever.
Behavior after fever control becomes the primary indicator of the need for these tests.
Secondly, the indications that demand a UA to rule out UTI become somewhat less aggressive.

Question 16

Over 24 Months of Age

Answer 16

The evaluation of fever in children over 24 months of age keys off of specific historical and physical findings such as: cough, rash, pharyngitis, ear pain, etc.
If there are no specific historical or physical findings around which to develop a list of possible diagnoses and the duration of fever is short-term (< 5 days), then the primary occult infection to be ruled out is a UTI in the female.

Question 17

Diagnostic Tests

Answer 17

As indicated by history and physical findings:
CBC with differential
ESR
Chemistry
U/A with culture
Blood culture
Spinal tap
Stool for blood and culture

Question 18

Differential Diagnosis

Answer 18

Bacterial infections
Viral infections
Elevations resulting from normal deviation – physical activity, ovulation, environmental heat, excess clothing
Leukemia
RA
CNS disorders affecting the hypothalamus

Question 19

Plan/Management

Answer 19

Assess parent’s ability to take and interpret temperature correctly
Oral temperature - for most children 5 years of age and older
Fever peaks about 6PM and is at its lowest point about 4AM
For each degree of fever, pulse increases 10 beats/minute
Respirations increase 2 cycles/minute
Encourage fluids to prevent dehydration
Clear are easiest to retain
Frequent, small amounts

Question 20

Anticipatory Guidance

Answer 20

Fever is not an illness but a physiologic response.
In otherwise healthy children, most fevers are self-limited and benign, provided that the cause is known, and fluid loss is replaced; fever does not cause brain damage. If there are signs of serious illness, a health care provider should be consulted.
There is no evidence that fever makes the illness worse.
Initial measures to reduce the child’s temperature include provision of extra fluids and reduced activity.
Fever may merit treatment with an antipyretic agent if the child is uncomfortable (as indicated by decreased activity level, decreased fluid intake, etc).
Decreased temperature after receiving an antipyretic agent does not help to determine whether the child has a bacterial or viral infection.
Children who are receiving treatment for fever do not need to be awakened to receive the antipyretic agent.
Children who are receiving antipyretic medications should not be given combination cough and cold preparations, which often contain antipyretic medications; giving both medications may lead to inadvertent overdose.

Question 21

Antipyretic Use

Answer 21

Fever in and of itself, secondary to an infectious cause, does not require antipyretic therapy. That said, there are many reasons to treat a fever.
These include:
1) reduce the risk of dehydration
2) improve the child’s comfort and most important
3) assess the child’s behavior independent of high fever.
Acetaminophen and ibuprofen are the two main antipyretics used in children.

Question 22

Antipyretic Use

Answer 22

Acetaminophen is given in a dose of 15mg/kg lean body weight up to the adult max of 500mg every 4 hours - (after 3 months of age)

Ibuprofen is given in a dose of 10mg/kg up to the adult max of 400 mg every 6 hours. That it can be administered every 6 hours is a definite advantage - (after 6 months of age)

**So important to calculate out the dose and write it down for the parents/caregivers

Question 23

Antipyretic Use

Answer 23

Alternating ibuprofen and acetaminophen is discouraged because ibuprofen decreases glutathione (an anti-oxidant) in the kidney, and the risk of renal damage from acetaminophen increases when glutathione levels are reduced.
Tylenol – 160mg/5mL
Ibuprofen – 100mg/5mL

Question 24

Follow-Up

Answer 24

Depends on degree of fever and etiology
With no established diagnosis, telephone contact should be maintained every 12-24 hours
Child should be re-evaluated if fever continues beyond 24 hours, if signs of toxicity occurs, or if any signs or symptoms of infection occur

Question 25

Consultation/Referral

Answer 25

Fever persisting over 5 days (FUO)
Acute high fever or prolonged high-or-low-grade fever
Infant under 6 months of age
Child with stiff neck, petechiae, swollen or inflamed joints, or dehydration
Tachypnea out of proportion to temperature elevation
Fever associated with seizure

Question 26

FW

Answer 26

Fever without source - fever for ≤1 week without adequate explanation after a thorough history and physical examination; FWS can progress to FUO if it lasts >1 week.

Question 27

FUO

Answer 27

Fever of Unknown Origin – fever in children >38.3°C (101°F) at least once per day for ≥8 days with no apparent diagnosis after initial outpatient or hospital evaluation that includes a detailed history, thorough physical examination, and initial laboratory assessment.