Haven’t you assumed that a rectal temperature always would be a more accurate measurement than an axillary reading? It seems to me that the closer one could get to the center of the child’s body, the more likely you would get a true reading – and the less likely you would fall victim to operator error. However, a study reported on the Pediatric News website suggests that our intuition is wrong again (“ Axillary thermometry is the best choice for newborns ,” by M. Alexander Otto, Aug. 24, 2017). In the study of 205 newborns at the University of North Carolina at Chapel Hill Medical Center, multiple temperatures were recorded using three methods over a 15-minute period. Rectal temperatures were accurate but less reliable than axillary readings, while temporal artery measurements tended to “overestimate temperatures by an average of about a quarter of a degree.”
At the Pediatric Hospital meeting in Nashville, Tenn., lead investigator Ketan Nadkarni, MD, stated that, based on the data, “we think axillary [thermometry] is what we should continue to use in the newborn nursery.” At first blush, this sounds like a very reasonable and rational recommendation, which I am sure will be greeted warmly by nursery nurses at his hospital and across the nation, if only as a way to save time cleaning bassinet linen. There are few things as good as a rectal thermometer at triggering an enteric explosion of meconium from a newborn who has been saving it up for a couple of trimesters.
However, before we jump on the no-rectal-temps in the nursery bandwagon, let’s look at the rectal probe not just as a way to assess a newborn’s temperature, but as a tool for examining the baby’s rectum. For a variety of reasons, the newborn perineum often seems to escape the careful examination it deserves, particularly if the initial exam is performed with the parents watching.
Of course, parents are interested in their baby’s hair and eye color, and whether it has the requisite number of fingers and toes. They will wait anxiously until you have lifted your stethoscope off the baby’s chest and given them a nod and smile. However, doing a thorough exam of the infant’s genitalia may appear a bit invasive and improper to some parents. Whether it is because we sense some unspoken parental discomfort or because we are trying to save time, the nether regions of little girls are inadequately examined.
My evidence for this unfortunate observation is the number of times I have discovered nearly complete labial fusion in an infant female who had allegedly had a complete well child exam 3 or 4 weeks previously. We can argue how aggressively one should treat the condition, but the scenario suggests to me that some providers are not doing thorough perineal exam on infants.
But back to rectal temperatures. It seems to me that it would be prudent to adopt a guideline that says that a newborn’s first temperature be taken rectally. Not because it is any more accurate than an axillary temperature – which this study suggests that it is not. But because the process of taking the temperature would make it more likely (I hesitate to say guarantee) that someone will be taking a careful look at the newborn’s rectum. That initial rectal temperature is not going to detect every genital anomaly, but it may help find some in a more timely fashion. If nothing else, it will get that meconium moving.
Dr. Wilkoff practiced primary care pediatrics in Brunswick, Maine, for nearly 40 years. He has authored several books on behavioral pediatrics, including “How to Say No to Your Toddler.”