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The Informed Parent

Why 100.4 Degrees?

by Louis P. Theriot, M.D., F.A.A.P.
Published on May. 31, 2004
The call came in around 9:30 at night. Mrs. Y. was phoning for some advice about her three-week-old infant, Brittany. “So sorry to bother you at home,” she said. “But I wanted to know the dose of Tylenol for Brittany. I don’t want to be an over-protective mother, but she was a little fussy...I thought she just might have gas,” she went on to explain. “And then she felt a little warm. I took her temperature, and it was only 100.6 degrees. I know that this isn’t much of a fever, but I was wondering if I should give her some Tylenol.”
I assured her that the phone call was most appropriate, and then obtained more information. It seems that Brittany was eating well. There were no respiratory symptoms. There was nothing to suggest diarrhea or vomiting. Her urine output was good which indicated that she was not dehydrated. “Just a bit fussy” was the report from mom. Mrs. Y. assured me that the temperature had been taken with a rectal thermometer. She remembered that this was the most accurate way to get an exact reading.
I had her repeat the temperature while I waited on the phone. Sure enough, it registered 100.6 degrees again. There was dead silence on the other end of the phone when I told Mrs. Y. to pack up some things for Brittany. I would immediately meet her in the office and arrange for the baby to be admitted to the hospital. The silence was interrupted by Mrs. Y. asking, “You’re joking of course...I mean, you’re NOT serious, are you?”
I indicated to her that I was MOST serious and everything would be explained when we met at the office. Both Mr. and Mrs. Y. came shortly after I arrived, with Brittany and diaper bag in hand. After they undress the baby I took her temperature again, myself. It registered 100.5 degrees rectally. Brittany’s exam was perfectly normal. While the parents put back on her clothes I called the hospital to arrange admission with a diagnosis of RULE OUT SEPSIS.
Newborns are defined as infants one month of age or younger. The immune system of these babies is not always fully mature. Their ability to handle an infection may not be reliable. When a newborn has a rectal temperature of 100.4 degrees or greater the standard of care, at least in the United States, is to admit them to the hospital, do the appropriate lab studies, and start them on antibiotics immediately. It may seem like an overreaction, or overkill, but this is to insure that no baby falls through the cracks. A newborn with this low grade temperature may simply have a little viral infection, or perhaps just be overly bundled...but they could also have a serious life-threatening bacterial infection. There is no way to predict which it is.
There are countless horror stories about newborns that were sent home from the emergency room after having a documented temperature of 100.4 degrees or greater. But their exam was completely normal and the baby looked like a rose. Within the next 24 hours that same baby is in the intensive care unit fighting for his/her life because they are septic. This means they have a bacterial infection in their blood stream. 100.4 degrees is a random number, but it allows a high enough level of suspicion to be sure no baby with sepsis will be missed.
Mr. and Mrs. Y. understood clearly why Brittany had to be admitted to the hospital and were comfortable with the decision. The baby had a complete blood count (CBC) and urinalysis, both of which were normal. She then had a blood culture, urine culture and spinal tap to rule out meningitis. These studies were done upon admission. She had an IV inserted and was started on IV antibiotics. I put her on Ampicillin and Gentamicin which are two standard antibiotics used for the treatment of presumed sepsis. This combination will cover all possible bacteria that would infect a newborn.
Brittany did just fine in the hospital. In fact, from the start of admission her temperature never went above 99.8 degrees. After 48 hours the lab indicated that her blood, urine, and spinal fluid cultures were “no growth”. This meant that they were negative. For cultures, the lab will plate the sample on a culture medium and literally incubate the specimen in an oven. These are read daily, and if bacteria is present they will grow after a certain amount of time. This is really the gold standard for identifying whether or not a newborn is infected.
In Brittany’s case the cultures were negative. She did great clinically and she was discharged home by the third day. Brittany’s story is fairly common and the outcome was excellent. Luckily true sepsis does not happen very often, but when it does, the results can be devastating. In the case of a newborn, one is not afforded the luxury of “watchful waiting” or letting things declare themselves as can be done in dealing with a toddler who just has a fever. And, as a clinician, it makes our job much easier because the standard is set. We don’t have to make a judgment call when confronted with a newborn having only a fever. If it is 100.4 degrees or greater it is an automatic admission to the hospital.

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