Be Still My Beating Heart: 5 explanations for an elevated pulse that you should know
Today I want to talk about some vital signs. These are important, right; they’re VITAL. And we need to have them all working (fairly) smoothly in concert to remain vertical, so I think it’s fair to give them some attention. Most of the time at work, before I even go into a room to examine a patient, I take a look at the vital signs as a way to frame up my assessment.
Let’s first say what the vital signs are:
- Pulse (or heart rate)
- Respiratory rate
- Blood pressure
One thing that I want everyone to know is that normal vital signs are different for different ages.
Kind of like in the animal kingdom, where little animals like hummingbirds have usual heart rates of over 200 beats per minute and elephants have rates of 40 per minute: the larger the creature gets, the slower the heart rate is. Same deal in humans. A heart rate of 145 in a baby is perfectly normal, but when I see that number for a teenager I get very concerned, or at least need a reasonable explanation for it.
Temperature and weight get addressed a lot, don’t they?
Between fever and obesity, many a blog has been written. Respiratory rate is a vital sign that usually makes itself known when there’s a problem: it’s hard NOT to notice when a child is in true respiratory distress. They’re breathing so fast that their chest and abdominal muscles are visibly moving in and out, and they can barely feed (baby) or speak (older child) due to that rapid respiratory rate. Blood pressure is a squirrely one in children: high blood pressure in kids is relatively uncommon, but as the childhood obesity epidemic grows, we are starting see more of it. See how vital signs interrelate?
Let’s get back to pulse.
That’s the number of times the heart beats in a minute. What I want to focus on today is on the heart rate, and specifically, a fast heart rate. The 25 cent word for this is tachycardia (pronounced ta-kick-ard-ee-uh), and it always gets my attention. I’m happy to say that most of the time in pediatrics it is easily explained by reasons OTHER than the heart, but that doesn’t diminish its importance. There are FIVE key reasons for the heart rate to be elevated in kids (adults too, for that matter):
Elevation of the body temperature alone causes the heart rate to increase. The chemicals in our cells that are associated with inflammation (due to whatever cause: infection, auto-immune reactions, etc.) produce a cascade of reactions that ultimately elevate our body temperature “set point”, and that’s why we have fever that hangs on until a fever-reducer medicine is given (acetaminophen or ibuprofen) or the infectious or inflammatory process goes away. Along with those chemical reactions come an increase in pulse, as the heart does its job to help pump along all the infection fighting inflammatory cells in the blood to the rest of the body where they are needed. Thanks, heart, for pitching in and doing your job.
When we exercise, our muscles need more oxygen to keep going, and as such, the heart rate increases to make sure the oxygen delivery is adequate. Simple as that. As we get better conditioned our muscles “process” oxygen more efficiently and that’s why athletes have lower resting heart rates. Totally normal.
When the body is low on fluids, the circulating volume of blood and plasma in your body decreases, and this causes the heart to pump faster in order to get that smaller amount of oxygenated blood to the other organs and tissues where’s it’s needed. Refer to the animal analogy from earlier: the smaller the body, the less volume reserve the body has. That’s why babies get dehydrated quicker than older kids. And it’s one of the MOST common reasons that the heart rate goes up. Again, thanks heart. See #1.
Actual heart problems
Kids can get abnormal heart rhythms, called dysrhythmias (diss-rith-mee-uhs…25 cents!) that cause the heart rate to increase. These are typically quite dramatic; I’ve had families say that they could see their child’s heart beating rapidly underneath their shirt from across the room! It’s not unusual for a rapid heart rate due to an actual cardiac cause to yield markedly high heart rates of over 200 beats per minute (BPM), compared to only moderately elevated heart rates due to other causes. Needless to say, a heart rate elevated over 200 BPM in ANY age group warrants an immediate and emergent evaluation, usually with heart monitoring and an ECG (electrocardiogram) tracing. I’m not gonna thank the heart for this one, since it needs to straighten up and act right.
Special shout out to THE most common medicine for causing kids to feel like their hearts are thumping away: ALBUTEROL, the friendly neighborhood wheezing medicine. Available in nebulizer or inhaler form, this medicine, while doing a beautiful job dilating and opening up the constricted airways, also has a direct effect on the heart to speed up the rate. In children, this is usually not a big deal and it goes away on its own after a bit of time, but it can be very annoying and distracting. I’ll take it temporarily though, if it means that breathing improves.
Other substances can cause the heart rate to increase: cocaine (yep, I’ve seen it in kids), and one that we always need to keep in the back of our mind- accidental ingestion of an adult family member’s medication. This happens more than we all think, even with our best intentions of keeping medicines away from children. Make sure you have the Poison Center’s phone number handy: 800.222.1222. Those folks are fantastic, and are available 24/7.
This list covers most of the important highlights of what goes through my mind when I see a child with an elevated heart rate. As you can probably conclude from a few of the points above, not every child who comes in with the complaint of “heart palpitations” needs a fancy ECG or X-ray. What they DO need is a full set of vital signs (and maybe a repeat set or two, to catch any potential discrepancies during the first set) and a thorough assessment by a solid clinician to determine the most likely cause. And now that YOU have some insight into what could be the explanation, you’ll be able to follow along the rationale without a stressful increase in YOUR heart rate as well.