What is Fever in a Neonate?
The World Health Organization divides a condition called neonatal sepsis into two categories, early and late, based on when it starts. Early neonatal sepsis affects babies who are less than 72 hours (some experts use 7 days as the cut-off). On the other hand, late-onset infections occur in babies who are older than 72 hours up to 28 days old. It’s crucial to spot and treat this condition quickly, as it can have serious health implications and could be fatal for the babies in this age range.
What Causes Fever in a Neonate?
Early-onset newborn sepsis, a serious infection in babies less than a week old, is mostly caused by a bacteria called Group Beta Streptococcal (GBS), and followed by another bacteria named Escherichia coli. The chances of a baby getting this infection are higher if the mother has the Group B streptococcal bacteria, develops an inflammation of the fetal membranes due to infection (chorioamnionitis), has a premature or prolonged (more than 18 hours) breaking of waters, or gives birth too early (before 37 weeks).
On the other hand, late-onset newborn sepsis refers to a severe infection occurring in babies who are more than a week old. This can be caused by several types of bacteria including Group B strep, E. coli, Coagulase-negative Staphylococci, Staphylococcus aureus, Klebsiella pneumonia, Enterococci (particularly common in preterm infants), Pseudomonas, and Candida albicans. Babies born prematurely, those with low birth weight, those who have had a catheter in for a long time, or those who had to undergo medical procedures are at a higher risk. Similarly babies who have complications like ventilator-associated pneumonia, or who have been treated with antibiotics for a long time are also more susceptible to late-onset newborn sepsis.
Risk Factors and Frequency for Fever in a Neonate
According to WHO statistics, there are over one million newborn (neonatal) deaths every year due to neonatal sepsis/pneumonia, making it the biggest cause of infant mortality globally. In the United States, the CDC estimates that early-onset neonatal sepsis (an infection that occurs early in a newborn’s life) affects 0.77 to 1 per 1,000 live births. Guidelines for universal screening and treating maternal GBS colonization (a bacteria that can cause severe infections in newborns) have led to fewer cases of early-onset sepsis in full-term babies, bringing it down to around 0.3 to 0.4 per 1,000 live births. However, the occurrence of late-onset sepsis (an infection that occurs later in a newborn’s life) remains the same, at approximately 0.4 per 1,000 live births.
Signs and Symptoms of Fever in a Neonate
Neonatal sepsis, a possible life-threatening condition in newborns, can be hard to spot due to signs being varied. The infant might have high or low body temperature, be excessively irritable or lethargic, and have rapid respiratory rate or even momentary absence of breath. Additional signs might include abnormal heart rates, difficulty feeding, being excessively sleepy, or acting fussy. Conditions like Necrotizing enterocolitis, pneumonia associated with the use of breathing equipment, and urinary tract infections are more common in premature babies. A physical check might be normal or show signs of neonatal sepsis.
Gathering a thorough history is crucial. This includes looking into risk factors related to both the mother and the baby. Risk factors tied to the mother include missed or late prenatal care visits, having group B strep bacteria, use of antibiotics during labor. The mother’s own medical history, such as having conditions like diabetes, high blood pressure, thyroid issues, or drug misuse could also add risks. For the baby, being born prematurely or with low birth weight increases risk. Detailed information about the baby’s time in neonatal intensive care unit, if the mother’s water broke prematurely, and exposure to any sick persons is also important to consider.
- High or low body temperature
- Excessive irritability or lethargy
- Rapid respiratory rate or absence of breath
- Abnormal heart rates
- Difficulty feeding
- Being excessively sleepy or fussy
Testing for Fever in a Neonate
When a newborn baby is thought to possibly have sepsis, a type of severe infection, they will need to have several tests. These tests may include a complete blood count, chemistry panel, and tests to check for the presence of certain diseases in the blood, urine, and cerebrospinal fluid (the fluid around the brain and spinal cord). Two other tests, named C-Reactive Protein (CRP) and procalcitonin, may also be used in combination with other factors to identify babies who are at risk of severe bacterial infection.
Depending on the baby’s symptoms, doctors may also want to test for respiratory or gastrointestinal pathogens (disease-causing microorganisms), RSV and influenza viruses, and might even do a chest X-ray. There are certain criteria, named after the cities they were developed in – Rochester, Philadelphia, and Boston – which suggest checking for sepsis in all babies less than 28 days old who have a fever, no matter what other risk factors they may have.
After a vaccine for streptococcus infection became widespread, the prevalence of bacteremia (bacteria in the blood) in babies with fever decreased. A ‘Step by Step’ approach, which involves assessing the risk for severe bacterial infection, is now being used to identify infants who are at a lower risk. Babies with fever who are at high risk for serious bacterial infection may have certain signs such as white blood cells in the urine, and elevated levels of procalcitonin (greater than 0.5 Ng/ml), CRP (greater than 20 mg/L) and ANC (a type of white blood cell, greater than 10,000/mm3).
Research has shown that the occurrence of bacterial meningitis (a severe brain and spinal cord infection) in combination with urinary tract infection is rare. Some babies who seem well but have a fever may not need laboratory studies done immediately, as only about a quarter of them will end up having a severe infection.
Recently, some medical centers are using a test that checks for pathogens in the CSF, which gives results in just two hours. This test is particularly useful during times of the year when enteroviruses are common, or if the CSF sample is contaminated with blood, as it can help distinguish between bacterial and viral infections.
Treatment Options for Fever in a Neonate
When a newborn appears unwell, it’s crucial to perform a thorough check-up for any type of infections. Broad-spectrum antibiotics like ampicillin and cefotaxime are usually administered because they can cover almost all types of bacteria causing early and late onset infections in newborns. However, there are some bacteria which cefotaxime cannot treat, and its use in the neonatal intensive care unit (NICU) can also lead to outbreaks of infections resistant to antibiotics. In certain cases, if there are concerns of a possible herpes infection in the newborn, treatment with the antiviral drug Acyclovir may be started. Newborns that appear unwell, or possess risk factors for an infection, are usually hospitalized and treated while tests are conducted to identify the specific bacterial cause.
If a newborn has septic shock, a serious condition that occurs when an infection leads to dropping blood pressure and organ failure, the treatment involves administering fluids rapidly. This is faster and involves more fluids in term newborns (born at the right time) compared to preterm newborns (born early). If this doesn’t work, then medications called vasopressors, which help tighten blood vessels and increase blood pressure, are used.
Based on test results, febrile infants (those with a fever) over 21 days old, who appear well and have no risk of severe infections, can be classified into three categories: high risk, medium risk, and low risk. This helps in deciding the course of treatment. Low-risk infants can be cared for at home or in the hospital without immediate treatment, while high-risk infants need to be treated in the hospital. Medium-risk infants can be observed at home or in hospital before deciding the need for empirical treatment. However, if there’s any confusion, it’s better to admit them in the pediatric unit for continuous observation while waiting for the culture test results to identify the specific bacterial cause.
What else can Fever in a Neonate be?
When a doctor is trying to make a diagnosis, these are some possible conditions they might consider:
- Low blood sugar (Hypoglycemia)
- Heart defects present at birth (Congenital heart disease)
- Genetic disorders that affect metabolism (Inborn defects of metabolism)
- Inability of the adrenal glands to generate enough hormones (Congenital adrenal insufficiency)
- Underactivity of the thyroid gland from birth (Congenital hypothyroidism)
- Child neglect/abuse
What to expect with Fever in a Neonate
The outlook is usually very good if a full-term newborn is treated early. However, the outlook can be different for premature or extremely premature infants.