The risk of serious bacterial illness (SBI) is greatest during the neonatal period, defined as birth to 28 days of life. Some authorities recommend that a child born prematurely should have the degree of immaturity subtracted from the child’s chronological age for this consideration.
It is generally accepted that a fever is a temperature of ≥38°C or 100.4°F taken with a rectal thermometer.
A neonate who had a documented fever by any method but is afebrile in the emergency department (ED) should be treated as a febrile neonate whether or not antipyretics have been given, as other methods of thermometry tend to underestimate the actual temperature.
The most frequent bacterial pathogens in the neonatal period are group B Streptococcus (GBS), Escherichia coli, and Listeria monocytogenes.
Hypothermia is a rectal temperature less than 36°C or 96.8°F, and in the neonatal period may actually be a more common presentation than elevated temperature. All neonates with hypothermia should be treated as septic.
Causes other than SBI, especially herpes simplex virus (HSV) infection, should be considered and, if suspected, treated expectantly.
Noninfectious problems, such as congenital heart disease (CHD), inborn errors of metabolism, and trauma, may present in a similar way and must always be included in the differential diagnosis of the septic-appearing infant.
If the child is exhibiting signs of shock, such as tachycardia, mottling, apnea, or prolonged capillary refill time, aggressive fluid resuscitation must be immediate.
Antibiotics should be started after cultures have been obtained.
If the child is unstable, the lumbar puncture may need to be postponed but should not delay empiric antibiotic therapy.
Fever is one of the most common presenting complaints of children evaluated in the emergency department (ED). Of particular concern to both parents and practitioners is the febrile neonate (0–28 days), since fever is often the only clinical sign of SBI in this age group. Neonates are at a particularly high risk of SBI due to a relatively immature immune system, including decreased T-helper cell activity, opsonization, antibody titers, macrophage, neutrophil, monocyte, and complement activity compared to older infants.1–3 Some authorities recommend that a child born prematurely should have the degree of immaturity subtracted from the child’s chronological age for this consideration. The resultant inability to adequately contain bacterial infections results in higher morbidity for neonates with SBI. In addition, due to developmental immaturity, clinical indicators of wellness are not universally present in the neonate. For example, acquisition of the social smile, one of the most commonly used signs to judge the clinical appearance of infants, generally does not develop until 4 to 8 weeks of age.
Fever is generally defined as a rectal temperature ≥38.0°C (100.4°F). Temperatures obtained by the axillary, otic, temporal artery, or noncontact mid-forehead infrared routes tend to underestimate the rectal temperature and are often unreliable.4 Neonates with a documented rectal fever obtained by a reliable caretaker at home or in the office setting, who are afebrile on presentation to the ED, have the same risk of SBI as those with documented fever who present initially to the ED. Therefore, they should be managed as febrile whether or not antipyretics have been given. Mild temperature elevation can occur secondary to environmental factors such as bundling; however, in this scenario, the neonate should be unbundled and have repeated temperature measurements to determine if there is fever. Subjective (tactile) fever determination by the parent is unreliable and does not place the neonate at higher risk for SBI. Hypothermia (≤36.0°C [96.8°F]) can also be a presenting symptom of SBI, and the evaluation should be the same as for a febrile neonate.
SBI is typically defined as the presence of a pathogenic bacterial organism in the cerebrospinal fluid (CSF), blood, urine, or stool. Many investigators consider the presence of a lobar infiltrate on chest radiograph to be indicative of bacterial pneumonia and therefore considered an SBI. The rate of SBI in the febrile neonate is >20%.5 Focal bacterial infections such as cellulitis, septic arthritis, omphalitis, and otitis media are typically managed as an SBI if the neonate is febrile.
The epidemiology of SBI has changed over the past several decades due to routine childhood immunization against two of the most previously common pathogens implicated in bacterial meningitis and bacteremia—Haemophilus influenzae type B (HiB) and Streptococcus pneumoniae. The incidence of HiB meningitis has decreased drastically since introduction of the vaccine; although S. pneumoniae remains one of the most common causes of bacterial meningitis, an overall decrease in the incidence of invasive pneumococcal disease reflects vaccine efficacy. Currently, GBS and Escherichia coli are the most common causes of bacteremia and bacterial meningitis in neonates. E. coli is the pathogen responsible for the majority of neonatal urinary tract infections (UTIs). Listeria monocytogenes is also a recognized pathogen in younger or premature neonates. Other bacterial pathogens in febrile neonates include Staphylococcus aureus, Salmonella sp., and other gram-negative organisms.
While emphasis is typically placed on identification of SBI in febrile neonates, viral infections occur more frequently than bacterial infections. While most viral infections are benign, some may result in serious illness. Neonatal herpes simplex virus (HSV) infection is rare (estimated 1500 cases/year in the United States); however, it carries risk of significant morbidity (primarily neurologic deficits) and mortality that can be reduced with appropriate antiviral therapy. Three different clinical presentations of neonatal HSV that may overlap exist: skin, eye, and mouth infection (45% of cases); central nervous system infection (30% of cases); and disseminated HSV (25% of cases).6 Respiratory viruses, such as influenza and respiratory syncytial virus (RSV), are fairly common in febrile neonates, especially in the winter months.
The differential diagnosis of the septic-appearing neonate is broad. Conditions other than sepsis are listed in Table 2-1.
Congenital adrenal hyperplasia (Chapter 78) Congenital heart disease (Chapter 40) Dysrhythmias (Chapter 43) Electrolyte disturbances (Chapter 81) Food protein–induced enterocolitis syndrome (FPIES) Hypoglycemia Inborn errors of metabolism (Chapter 80) Nonaccidental trauma (Chapter 145) Toxic exposure Volvulus (Chapter 46) |
