Posted tagged ‘thermometer’

The best thermometer for measuring fever in a child is….

May 9, 2013

The Pediatric Insider

© 2013 Roy Benaroch, MD

There are lots of choices, so which one is best? Which kind of thermometer should parents buy and use?

Keep in mind that body temperature is one measurement—but it’s certainly not the only measurement, and it’s far from the most important way of knowing if your child is ill. Kids can be seriously sick without a fever; and almost all ordinary children with fever do not have a serious illness. There’s far too much “fever phobia” out there, and there’s already far too much preoccupation with whether Junior has a fever and how high the temperature is. Fever itself doesn’t hurt anyone. It doesn’t cause any damage, and won’t hurt your child. But fever can make your child feel sick, so it’s worthwhile to treat it. Safe medicines for fever can help your child feel more comfortable.

Also, any discussion of fever needs a caveat: all of this information is only for healthy, otherwise-well children with no immune-compromising condition. That means children who have NOT gotten all of their vaccines are NOT healthy and otherwise-well, and have a much greater risk of serious, even overwhelming infection. If your child isn’t up to date on vaccines, I offer no advice on how to measure or handle temperatures. Call your doctor. Better yet, unless there is a medical contraindication, get your child caught up on vaccines, pronto. You wouldn’t drive without your child in a safety seat, would you?

Another fun fever fact, before we get to the meaty stuff: if anyone has told you that 98.6 F is the “normal” temperature, they’re wrong. It’s not normal, it’s average. 98.6 is no more the normal than saying 5’10” is the normal male height. As with every other measurement in nature, temperatures vary among individuals, and temperatures vary throughout the day. 98.6 is the average, meaning that normal ranges from below this to above this. In most circumstances, most pediatricians consider anything measured at 100.4 or above to be a fever. Values measured below that threshold are not “low grade fevers”—they’re normal temperatures. And don’t start adding degrees, depending on how you measured the temp. That just confuses everyone.

So what are the choices for thermometers, and which should you choose? I’m going to include links here to Amazon products, just so you know what I’m talking about. (I have no financial relationship, and I don’t care if you buy through these links, etc.)

Mom or dad’s hands: These actually make a reasonably good thermometer, at least for “ruling out” fever. If you touch your children, and they do NOT feel warm, they almost certainly do not have a fever. The inverse of this, by the way, is not true: often your child will feel warm, and won’t actually have a fever—so touch can rule out fever, but cannot confirm or measure a fever. But it’s a start, and for busy people with older, healthy kids, using your hands alone is not an unreasonable way to check.

Rectal thermometer: These work, though they’re slow. They’re also the only method used in most studies of small babies less than 2-3 months of age, so typically that’s what pediatricians want you to use at that age. But please, no rectal temps in older kids, OK? It’s just creepy and unnecessary.

Axillary thermometer, AKA “The Chicken Wing”: These work, though they’re also kind of slow. Not bad for an estimate. Kids feel silly sitting there holding their arms still, but that’s the price they have to pay.

Oral thermometer: Those old, mercury-filled ones you have to shake back down have gone the way of the dinosaurs. They’re all digital now, and they read faster. And if you shake one down after reading it people will edge away from you and give you odd looks. These work about as well as the others in this list.

So far, rectal/axillary/oral, it’s all good, at least when they’re appropriate for the age. But they’re all old school. Isn’t there something newer that’s better?

Binky-temps (AKA: a digital thermometer built into a pacifier): Please. This measures, maybe, the temperature of the top of the tongue, wherever that’s been lately. Don’t waste your money.

Forehead tape thermometers: These have vague glowing numbers that indicate, well, where the vague glowing numbers are. Might as well make up a temperature rather than rely on these things.

Infrared thermometers: The ones marketed to parents are sometimes called “non-contact” thermometers, because these don’t actually touch your child. They’re also sold at hardware stores to measure the surface temps of things from quite a long way away, like industrial transformers or crème brulee. They are not suitable for people-use, because they only measure surface temperature. We want core temperature, or the temperature of the blood as it exits the chest. The temperature of the skin is NOT an acceptable or accurate way to measure core temps.

Forehead thermometers:  One company sells a digital version of what’s essentially your hand, touching your child’s forehead. Use your own appendages instead, they’ll be just as accurate, and they’re much more handy! (Get it? Handy?! Hahahahaha. Hem. Sorry.)

Ear thermometers: Supposedly these measure the temperature in the middle ear, where the monkeys live (or so I’ve been told.) Several years ago, a company that will remain nameless (hint: the name rhymes with mermo-flan) gave my practice a dozen or so of these, so we could try them out. I guess they figured we’d love them, and patients would see us using them, and they’d rush out and buy them too. Trouble is, the darn things were terrible—they missed high temps, they inflated no-temps, they gave children random fevers. So we threw them all away. If you’ve already bought one, maybe you can repurpose it as a chicken cutlet pounder or decorative paperweight.

Temporal artery thermometer: I’ve save the best for last! It’s quick, it’s easy, and a recent study showed that it’s pretty much as good as a rectal temp.

So: if your child feels warm, and you’d like to measure the temp, a temporal artery thermometer may be the best way to go. They’re more expensive than an ordinary digital thermometer for oral or axillary use, but they’re faster and I think they’re easier to use.

We have a winner!

More about fevers:

The fever action plan

Why do people get fevers?

Medicines for treating fever

Should temperatures rise during sleep?

July 30, 2012

The Pediatric Insider

© 2012 Roy Benaroch, MD

“My son is 5 and he has no signs of being sick. But I have been noticing that his body is hot to the touch and his temperature is high (101 – 102) while he is sleeping. In the daytime he is usually around 98.6 or 99, but it worries me when he sleeps because it always goes high. Is this normal?”

Normal body temperature varies throughout the day. The lowest point is usually from 2-6 am, rising about 1 degree F through the day until a peak in the late afternoon. Measured temperature also varies with activity and ambient temperature, and can be influenced even by hunger and sleepiness.

It is a myth that 98.6 is “The Normal Temperature,” just like it would be a myth that 5’10” is “The Normal Height” for adult men. 98.6 is considered the middle of the range of normal, but even that isn’t very accurate, as different people will vary around their own “normals”. The 98.6 is more of historical interest than a medically exact measurement. It was figured out in the 19th century using thermometers that were incorrectly calibrated, and it’s actually wrong– but we’re kind of stuck with it now.

Since your son isn’t acting sick at all, why are you taking his temperature? An elevated measured body temperature can be a sign of illness, but really that’s only when a child is acting sick with symptoms. A measured temperature that’s higher than expected in a child who’s acting well and feeling well is probably just normal variation rather than a sign of disease.

If you’re worried, take him in for a good exam with his doctor, and bring your temperature logs. Write down the actual numbers from the thermometer, and write down how you measured them (what kind of thermometer). Don’t rely on ear temps or those skin-sensor devices, they don’t work to accurately measure temperatures.

More about fever:

What is it?

Why do kids run fevers

Dispelling fever phobia

The Fever Action Plan

Fever part 2: Why?

June 8, 2009

Normal body temperature is regulated in an area at the base of the brain called the hypothalamus. By the release of hormones and neurologic signals, the hypothalamus can instruct the body to raise its temperature (by gearing up heat-producing metabolic pathways), or lower the temperature (by shivering. sweating, and increasing blood flow to the skin.) Conceptually, we think that the hypothalamus has a very sensitive temperature “set-point”, and that it continuously monitors the temperature of the blood to make adjustments in the body, keeping the temperature as close to the set-point as possible.

Fever occurs when the hypothalamic set-point is temporarily changed. This can occur via a variety of mechanisms, often involving molecules called “pyrogens” than can be released by a variety of immune cells in the body. Pyrogens are also found as components of certain bacteria.

“Hyperthermia” occurs when the body’s temperature rises above normal, but it is different from fever. In fever, the hypothalamus’ set-point is altered, and the body “wants” to get to the new set temperature by using normal physiologic mechanisms. In hyperthermia, excess heating occurs because heat from the environment is so high and sustained that it overwhelms the body’s ability to cool itself off. Think of a football player in full gear in August—it might be 100 degrees out, and if dehydration occurs there won’t be any sweat left to cool the body off.  The hypothalamus wants to cool off, but there isn’t any way to do this. In hyperthermia, the body’s temperature can get so high that tissue damage occurs. The best way to avoid hyperthermia is to consume plenty of fluids, and to get out of the hot sun at the first signs of heat illness (often nausea, headaches, and warm & dry skin.)

Unlike in hyperthermia, during a fever there is no outside source of heat, and the body cannot heat up enough to cause itself damage. As long as a child or adult with a fever stays well hydrated, the fever itself will not cause any harm, though it can make the person feel lousy.

So what’s the point of a fever—why does the body have mechanisms in place to raise the set-point? There is evidence that fever may be beneficial in fighting at least some infections. Fever allows white blood cells to proliferate faster, and helps them migrate through tissue better. It also increases the virus-fighting ability of interferons, and may decrease the ill effects of some bacterial toxins. It’s also thought that an overly warm environment may be less hospitable to bacteria that have developed in a way to thrive best at normal body temperatures. However, despite these observations there isn’t strong data that fevers overall really change the outcome of most infections, at least in the developed world where general health, nutrition,  and access to health care is good.

If fever is at least theoretically helpful in fighting infections, should we be using medicines to reduce fevers? I think so. Fever does cause some tangible ill effects in people, especially children. It increases fluids losses (contributing to dehydration), and increases metabolic energy demands. More importantly, though, it makes people feel bad. People with fevers can be achy and miserable. In my mind, helping the child feel better trumps any theoretical benefit from allowing the fever to continue untreated.

Most commonly, fever is treated by using medications to lower the hypothalamic set-point back towards normal. This is how ibuprofen and acetaminophen work. Alternatively (or in addition), parents can try to help their children reduce excessive heat by using cool (not cold) packs, or bathing in tepid water (never cold water, and never alcohol.)

Fevers occur when the body decides to reset the temperature at a higher level, most commonly as part of fighting an infection. It may serve a useful purpose, though the evidence for a practical benefit in most circumstances is sparse. Ordinary fevers can’t hurt anyone, but if your child feels bad with a fever, using medicine to help him feel better is a good idea.

Fever part 1: What is it?

June 1, 2009

The normal human body temperature is thought to average 98.6 F. We all remember this from elementary school, and I’ll bet many of you remember the old glass thermometers, the one your mom used with the little red line right at 98.6. If you could top that, you got to stay home! But, like so many things we were told in elementary school, the truth is more complex and murky.

The classic 98.6 is based on a book by Carl Reinhold (sometimes his name is given as “Carl Reinhold August Wunderlich,” a wonderful name that I hope comes up in casual conversation this week). In 1868 he published The Course of Temperature in Diseases, in which he hand-calculated the averages of about a million measurements in 25,000 patients, coming up with 37 C (=96.8 F). He also declared that based on his observations, 38 C (100.4 F) was the upper limit of the normal temperature, essentially defining “fever” for the first time. It turns out that his thermometers weren’t calibrated very well, and were probably off by at least 1 or 2 degrees, but he gave it a good try—especially considering that his thermometer was a foot long, and took twenty minutes to register a stable measurement. (I don’t know where he put that in his patients, and I’m not sure I want to know.) More recent research pegs the average temperature at 98.2 F, but even this varies at least one degree between individuals. One’s own temperature can also vary at least one degree based on the time of day (normal temperatures are lowest first thing in the morning, unless you’re ovulating.) There is also evidence that carefully measured temperature averages vary between human races and genders (women tend to run hotter than men—no surprise there.) Thought it’s not technically correct, 98.6 F (37 C) still remains widely accepted as the “normal” human body temperature for everyone at any time.

If 98.6 F is the traditional (though inexact) definition of “normal”, then what’s a fever? There isn’t a universal definition. Most pediatricians consider a rectal temperature above 100.4 to be a fever; in adults, the number 100 is more often used, usually referring to an oral temperature (though in the elderly, normal “resting” temperatures may considerably lower than 98.2 F). Measuring rectal temperatures becomes more difficult past a few months of life, so often an armpit, oral, or forehead temperature is measured. To be clear in communicating with your pediatrician, say the number that the device recorded, followed by the method you took it: “Junior was 100.8 degrees measured orally.” Don’t add or subtract degrees to “correct” the temperature, just tell us what the number is. In most cases outside of the newborn period, the exact number is not actually very important, but we do like to have a general idea of how high the fever was.

Fever occurs in children most commonly from infections, but can be a result of many other rarer problems (such as adverse reactions to medicines, inflammatory arthritis, cancer, and thyroid disease). Fever can also occur as part of “heat stroke,” when dehydration combined with exposure to heat overwhelms the body’s capacity to control its temperature. Victims of heat stroke feel warm and dry—not sweaty—and are often delirious or sleepy.  This is a true medical emergency that can lead to kidney failure, brain damage, and death. It’s the only health condition where fever itself contributes to harm.

This is the first post in a little series I’m writing on fevers. In future posts, we’ll explore what fevers are for, why parents don’t need to fear fevers, and a super-simple “pediatric insider” action plan for parents to follow when their child runs a fever. Stick around!