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 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 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 months will be hypothermic instead (See ED Clinical Pathway for Evaluation/Treatment of Febrile Young Infants (0-56 Days Old); https://www.chop.edu/clinical-pathway/febrile-infantemergent-evaluation-clinical-pathway ) 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 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 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