68
U N I T 1
Cell and Tissue Function
Fever in Children
Fever occurs frequently in infants and young children
(i.e., ages 1 day to 3 years) and is a common reason for
visits to the clinic or emergency department.
42,43
The dif-
ferential diagnosis of fever is broad and includes both
infectious and noninfectious causes, with the majority
of febrile children having an underlying infection. The
most common causes are minor or more serious infec-
tions of the respiratory system, gastrointestinal tract,
urinary tract, or central nervous system. The epidemiol-
ogy of serious bacterial disease has changed dramatically
with the introduction of the
Haemophilus influenzae
and
Streptococcus pneumoniae
vaccines in developed
countries.
H. influenzae
type b has been nearly elimi-
nated and the incidence of pneumococcal disease has
declined substantially. Febrile children who are younger
than 1 year of age and females between 1 and 2 years of
age should be considered at risk for a urinary tract infec-
tion (see Chapter 24).
While most children have identifiable causes for their
fevers, many have fevers without localizing signs or
symptoms. These fevers, which are usually of rapid onset
and present for less than a week, are commonly referred
to as
fever without source
. The American College of
Emergency Physicians has developed clinical guidelines
for use in the treatment of previously healthy infants
and children ages 1 day to 3 years with fever without a
source. The guidelines define fever in this age group as a
rectal temperature of at least 38°C (100.4°F). The reli-
ability of other methods of temperature measurements
(e.g., axillary, ear) is lower and must be considered when
making decisions about the seriousness of the fever.
43
The approach to the young child who has fever with-
out a source varies depending on the age of the child
(neonate [0 to 28 days], young infant [1 to 3 months],
and older infants and toddlers [3 to 36 months]).
44
All
have decreased immunologic function and are more com-
monly infected with virulent organisms. Neonates are at
particularly high risk for serious bacterial infections that
can cause bacteremia or meningitis. Also, neonates and
young infants demonstrate limited signs of infection,
often making it difficult to distinguish between seri-
ous bacterial infections that require immediate medical
attention and other causes of an elevated temperature.
Fever without source in children younger than age
3 months requires careful history and physical exami-
nation.
42
The temperature-lowering response to anti-
pyretic medications does not change the likelihood of a
child having a serious bacterial infection and should not
be used as an indicator of infection severity.
45
Neonates
with signs of toxicity (and high risk) including leth-
argy, poor feeding, hypoventilation, poor tissue oxy-
genation, and cyanosis usually require hospitalization
and treatment with antibiotics. Diagnostic tests such as
white blood cell count, blood and urine cultures, chest
radiographs, and lumbar puncture usually are done to
determine the cause of fever. Infants with fever who
are considered to be at low risk for bacterial infections
often are managed on an outpatient basis provided the
parents or caregivers are deemed reliable. Older chil-
dren with fever without source also may be treated on
an outpatient basis.
Fever in the Elderly
In the elderly, even slight elevations in temperature may
indicate serious infection, most often caused by bacteria,
or disease. This is because the elderly often have a lower
baseline temperature (36.4°C [97.6°F] in one study)
than younger persons, and although their temperature
increases during an infection, it may fail to reach a level
that is equated with significant fever.
45,46
Therefore, it
has been recommended that the definition of fever in the
elderly be expanded to include an elevation of tempera-
ture of at least 1.1°C (2°F) above baseline values.
The absence of fever may delay diagnosis and initia-
tion of antimicrobial treatment. Unexplained changes in
functional capacity, worsening of mental status, weak-
ness and fatigue, and weight loss are signs of infection
in the elderly and should be viewed as possible signs of
infection and sepsis when fever is absent. A thorough
history and physical examination are critically impor-
tant.
47
The probable mechanisms for the blunted fever
response include a disturbance in sensing of tempera-
ture by the thermoregulatory center in the hypothala-
mus, alterations in release of endogenous pyrogens, and
the failure to elicit responses such as vasoconstriction
of skin vessels, increased heat production, and shiver-
ing that increase body temperature during a febrile
response.
Another factor that may delay recognition of fever in
the elderly is the method of temperature measurement.
Oral temperature remains the most commonly used
method, but research suggests that rectal and tympanic
membrane methods are more effective in detecting fever
in the elderly.
47
This is because conditions such as mouth
breathing, tongue tremors, and agitation often make it dif-
ficult to obtain accurate oral temperatures in the elderly.
SUMMARY CONCEPTS
■■
The systemic manifestations of inflammation
include the effects of the acute-phase response,
such as fever and lethargy; increased erythrocyte
sedimentation rate (ESR), levels of C-reactive
protein (CRP), other acute-phase proteins, and
white blood cells; and enlargement of the lymph
nodes that drain the affected area. In severe
bacterial infections (sepsis), large quantities
of microorganisms in the blood result in the
production and release of enormous quantities
of inflammatory cytokines and development of
what is referred to as the systemic inflammatory
response syndrome.
