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“Approach to Fever” by Eli Freiman for OPENPediatrics

November 8, 2019


Approach to Fever,
by Dr. Eli Freiman. By the end of this
video, the learner will be able to summarize
the clinical basics of fever, describe the physiology of
body temperature regulation and the pathogenesis
of fever, and discuss the approach to
evaluation and management of a fever in a child. Introduction. Body temperature is
generally measured in four different ways– oral, rectal,
axillary and infrared. Rectal measurement is
considered to be the reference standard for measuring
body temperature, but is contraindicated
in neutropenic patients and is generally avoided
in older patients due to patient discomfort. Oral temperatures
run about 0.6 degrees Celsius lower and are
heavily influenced by recently ingested liquids
and respiratory rate. Infrared measurements
utilize technology to measure heat produced by
either the tympanic membrane or temporal artery,
and are widely used in the hospital and
emergency department setting. However, data are not conclusive
about diagnostic utility. Axillary measurements
are considered to be the least reliable
and often run lower than rectal temperatures. The mean normal
temperature for adults is 37 degrees Celsius, while
children and infants have a higher average temperature. Fever is defined differently
in different age groups, in part, because
of the epidemiology of invasive,
bacterial infections. In children under
three months old, we have a lower
temperature threshold to trigger an infectious workup. Some institutions choose to
call a fever 38 degrees Celsius. For older children,
the temperature that might trigger
an infectious workup may be higher, like
38.5 or 39 degrees. Remember however,
that fever should only be a piece of the larger
clinical evaluation when deciding how deeply to
investigate a certain patient presentation. And lower temperature should
not preclude investigation of an ill-appearing patient. Patients with specific
underlying conditions that increase the risk of
infection such as sickle cell disease, neutropenia,
or HIV, should be investigated thoroughly
with any concerning elevation in temperature. Physiology. Fever is an elevation
in body temperature mediated by
hypothalamic pathways in the central nervous system. The hypothalamic
thermoregulatory center controls body temperature
through three mechanisms. One– controlling
heat production mainly in the muscles and liver, two–
controlling heat dissipation from the skin and
lungs, and three– setting the normal
body temperature. Fever is a physiologic process
where the hypothalamus sets a higher body temperature set
point in response to endogenous signaling. The body then rebalances heat
production and dissipation to elevate the body temperature
to the new set point. This is why patients
with new fevers often feel cold and
experience rigors. Their current body
temperature, although elevated above true normal, lives below
the newly elevated hypothalamic set point and lead to the
subjective feeling of cold. Pathogenesis. Peripheral phagocytes release
various cytokines in response to encountered foreign
antigens or injury, including IL-1, IL-6,
TNF-alpha, and interferon. These cytokines then act on
the anterior hypothalamus, resulting in the upregulation
of prostaglandins, especially PGE-2, which results
in an increase in the hypothalamic set
point for body temperature. With a new higher set point, the
body increases heat generation through processes such as
increased metabolic rate, increasing muscle
tone or contraction, and decreasing
epidermal heat loss by modulating skin perfusion. Combined, these result in
higher body temperature to meet the newly increased
hypothalamic set point and result in clinical fever. Initial Fever Evaluation. Initial evaluation of all fevers
starts with a thorough history and physical exam with an
emphasis on the adequacy of cardiopulmonary physiology. Thorough histories
and physical exams can, with the
exception of neonates, often pinpoint the
likely source of fever. Signs of other underlying
diseases should be evaluated. Remember that response
to antipyretic therapy does not differentiate between
viral or bacterial etiologies. In the pediatric
history, important pieces of information to
elicit are, but are not limited to, headache
and photo phobia, ear tugging or pain, sore
throat, neck pain, swelling, or decreased range of
motion, cough and shortness of breath, costovertebral
angle tenderness or dysuria, focal abdominal
pain, vomiting, or diarrhea, rash, or focal limb or
joint pain or swelling. On exam, be mindful
to assess for evidence of altered perfusion
by evaluating for abnormal vital signs,
altered mental status, mottled skin, or delayed
capillary refill. Patients who are ill-appearing
or have unstable vital signs should have a broad infectious
workup, empiric antibiotics, and be admitted to
higher levels of care. Infants younger than 90
days are at significant risk for serious
bacterial infections, or SBI, for example, urinary
tract infection, bacteremia, or meningitis, or
even disseminated herpes simplex virus,
or HSV infection, without overt symptoms. There are specific
protocols governing the evaluation of
febrile infants 90 days of age and younger. Protocols vary by institution,
but generally involve blood, urine, and
cerebrospinal fluid, or CSF, tests via
lumbar puncture with bacterial cultures. The youngest infants are
also commonly evaluated for invasive HSV infection,
specifically HSV meningitis, by sending HSV PCR from the CSF. Decision whether to test
for HSV meningitis often depends on age,
specific risk factors, and whether there is
a CSF pleocytosis. The goal of such evaluations
is to identify infants at risk for SBI and HSV for
hospitalization and empiric antimicrobials. However, common viral
illnesses, such as respiratory syncytial
virus, RSV, or enterovirus remain the most common
cause of fever in infants under 90 days of age. Unlike infants less
than three months old, children ages three
to 36 months old are epidemiologically
at lower risk for serious bacterial
illness and are more able to communicate
their symptoms. Children in this age group
who, after a thorough history and physical exam, are
well-appearing but do not have a clear source
of fever, are often identified as having fever
without a source, or FWS. The majority of
patients with FWS have self-limited
viral infections or quickly develop a
recognizable source of bacterial infection. Fever without a source
is different than fever of unknown origin, or FUO,
which is when a fever has been present for eight or more days. FUO will not be discussed here. Types of serious bacterial
illness in this age group include meningitis, periorbital
or orbital cellulitis, septic arthritis,
osteomyelitis, UTI, pneumonia, and skin infections. Initial evaluation of
well-appearing children between three to 36
months old with FWS includes urine testing
for higher risk patients, such as girls less
than 24 months, uncircumcised boys
less than 12 months, and circumcised boys
less than six months. Routine laboratory evaluation
and empiric therapy for patients outside of
the high-risk age groups is not recommended. It is very important
that immunization status is included in the history
for these patients. Patients with FWS who have
not been completely immunized should routinely receive
screening blood and urine infection studies. Many guidelines recommend
empiric antibiotics in incompletely immunized
patients with leukocytosis. Management of Fever. As we previously discussed, the
first step in treating fever is determining the
cause, as the underlying etiology will guide management. Treatment for all of the
potential causes of fever will not be covered
in this video. Instead, we will focus
on symptomatic management of fever. In otherwise healthy children
with minimal symptoms, treatment of fever with
antipyretics is not required. Despite multiple studies,
there is no conclusive evidence that treating fever, as opposed
to the underlying condition, reduces morbidity or
mortality, except in cases where reducing metabolic
demand is important. The decision to
treat fever should be made on a case-by-case basis. The benefits of
antipyretic therapy include improvement in
the child’s discomfort, a decrease in insensible
losses to prevent dehydration, and analgesia. Potential downsides include
delayed identification of the underlying etiology,
drug toxicity, and allergy. The most commonly
used oral antipyretics are acetaminophen and ibuprofen. Antipyretics work in part
by blocking prostaglandin synthesis and restoring the
hypothalamic thermoregulatory set point to normal. Remember not to use
aspirin in children due to the risk of
Reye’s syndrome, except under very
specific circumstances. Sometimes, providers
will choose to not use antipyretics in order to monitor
the trajectory and amplitude of the patient’s fever curve. Thank you for watching this
video on approach to fever.

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1 Comment

  • Reply bye bye April 24, 2019 at 5:03 pm

    Measurement in the ear?

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