Pediatric emergency medicine trisk 363

CHAPTER 73 ■ SEPTIC-APPEARING INFANT
STEVEN M. SELBST, BRENT D. ROGERS

INTRODUCTION
A young infant may be brought to the emergency department (ED) because he or
she “just doesn’t look right” to the parents. Inexperienced parents will notice
when their newborn is unusually sleepy, fussy, or not drinking well. To the
clinician, such an infant may appear quite ill with pallor, cyanosis, or ashen color,
and have noted irritability, lethargy, fever, or hypothermia. Tachypnea,
tachycardia, hypotension, or signs of poor perfusion may also be apparent.
Generally, an ill-appearing infant will be immediately thought to have sepsis
and managed reflexively. Although this is the correct approach, several other
conditions can produce a septic-appearing infant. This chapter establishes a
differential diagnosis for infants in the first 2 months of life who appear ill. An
approach to the evaluation of such infants is discussed.

DIFFERENTIAL DIAGNOSIS
Numerous disorders ( Table 73.1 ) may cause an infant to appear septic. The most
common of these diseases ( Table 73.2 ) include bacterial and viral infections.
The remaining disorders demand diagnostic consideration because although
uncommon, they are potentially life-threatening and treatable.

Sepsis
Sepsis should always be considered when managing an ill-appearing infant (see
Chapters 7 A General Approach to the Ill or Injured Child , 10 Shock , and 94
Infectious Disease Emergencies ). The signs and symptoms of sepsis may be
subtle, and include lethargy, irritability, diarrhea, vomiting, and anorexia. Fever is
often present, but some septic infants younger than 2 months will be hypothermic
instead. (See ED Clinical Pathway for Evaluation/Treatment of Febrile Young
Infants (0-56 Days Old); ). The history may vary, and some infants
are ill for several days whereas others deteriorate rapidly. On physical

examination, a septic infant may be pale, ashen, or cyanotic with cool and mottled
skin due to poor perfusion. The infant may be lethargic, obtunded, or irritable.
There is often marked tachycardia, (heart rate approaching 200 beats per minute)
and tachypnea (respiratory rate more than 60 breaths per minute). If disseminated
intravascular coagulopathy (DIC) has developed, scattered petechiae or purpura


may be evident. A bulging or tense fontanel may be found if meningitis is
present. Otitis media, abdominal rigidity, joint swelling, tenderness in one
extremity, or chest findings such as rales indicate the infection has localized. Soft
tissue infections from MRSA are becoming a more common cause of sepsis.
Always examine the neonate for signs of omphalitis, an ascending infection
originating in the umbilicus. Finally, if the disease process has progressed, the
infant may develop shock and hypotension.
The laboratory is often helpful in suggesting a diagnosis of sepsis; however,
definitive cultures require time for processing. Potential abnormal laboratory
studies include a complete blood count (CBC) with a leukocytosis or leukopenia
with left shift, a coagulation profile with evidence of DIC, and blood chemistries
with hypoglycemia or metabolic acidosis. Recent risk stratification criteria utilize
elevated c-reactive protein (CRP) and procalcitonin (PCT) to identify infants at
high risk for serious bacterial infection. If localized infection is suspected,
aspiration and Gram stain of urine, joint fluid, spinal fluid, or pus from the middle
ear may reveal the offending organism, and a chest radiograph may show a lobar
infiltrate if pneumonia is present. Cerebrospinal fluid (CSF) cultures are
diagnostic for meningitis, and polymerase chain reaction (PCR) tests for CSF are
now readily available to screen for the most common viral and bacterial
etiologies. A promising new approach, in development, is the identification of
differing host mRNA response patterns to specific pathogens, which can be
determined more quickly than waiting for culture results.

Other Infectious Diseases
Overwhelming viral infections may cause systemic inflammatory response
syndrome (SIRS) and sepsis (see Chapter 10 Shock ). Approximately, 25% of
infants younger than 1 month with enteroviral infections develop sepsis, with
high mortality. Respiratory distress, hemorrhagic manifestations of the
gastrointestinal tract and skin, seizures, icterus, splenomegaly, congestive heart
failure, and abdominal distention often occur. Viral isolates from stool and CSF or
enterovirus PCR of the CSF may confirm the offending enterovirus.
Epidemics of respiratory syncytial virus (RSV) occur in the wintertime,
leading to respiratory distress, cyanosis, or apnea. Premature infants or those with
previous respiratory or cardiac disorders are especially susceptible to apnea.
Knowledge of illness prevalence in the community and wheezing on chest
examination may lead to the suspicion of RSV bronchiolitis. Some infants
develop wheezing later in the course, making the initial diagnosis in these
patients difficult. A rapid nasal wash test for RSV will be quickly diagnostic, and
a more expensive respiratory viral panel will diagnose other viral pathogens


within a few hours. A CBC may show a lymphocytosis with a left shift, and chest
radiographs may sometimes demonstrate diffuse patchy infiltrates or lobar
atelectasis.
Herpes simplex infections usually cause systemic symptoms and encephalitis at
7 to 21 days of life. Neonates present with fever, coma, apnea, fulminant
hepatitis, pneumonitis, coagulopathy, and seizures. History of maternal genital
herpes should lead to suspicion of systemic herpes infection in the neonate,
though the mother may be completely asymptomatic. Focal neurologic signs and
ocular findings (conjunctivitis, keratitis) may be noted. Vesicular lesions on the
skin are highly indicative of this infection, but they are present in only one-third
to one-half of patients. Rapid diagnostic studies include antigen detection tests
and enzyme-linked immunosorbent assay (ELISA) antibody tests. The Tzanck

preparation has low sensitivity and is not recommended. Direct fluorescent
antibody staining of vesicle scrapings is specific but less sensitive than culture.
PCR is a sensitive method to detect the virus from CSF in infants suspected of
herpes encephalitis and an electroencephalogram (EEG) or computed tomography
(CT) scan may also be helpful to reveal abnormalities of the temporal lobe. The
Magnetic Resonance Imaging (MRI) is preferred over CT but may be logistically
difficult. The diagnosis is confirmed by culture of a skin vesicle, mouth,
nasopharynx, eyes, urine, blood, CSF, stool, or rectum.


TABLE 73.1
DIFFERENTIAL DIAGNOSIS OF THE SEPTIC-APPEARING INFANT