Hello Evil Readers! I have returned!
Welcome back to the Ask Dr. Dina series of posts covering medical issues in your writing.
For those just joining us for this series, so far we've covered:
Loss of Consciousness
Altered Levels of Consciousness
Soft tissue injuries like sprains and strains
Cuts and Punctures
and infection, which was divided into four parts: bacterial, viral, fungal, and treatment.
Now that you're up to speed on all we've done so far, let's go on.
Today I want to talk about body temperature.
Humans are an interesting species. They're homeostatic creatures (remember science class? "Homeostasis" [loosely defined] = keeping things the same [stable] inside despite what's going on outside), which is important when it comes to things like body temperature.
What this means is that, no matter the weather, humans body temps need to stay about the same in order for them to function. Unlike reptiles ("cold-blooded" animals whose body temp is regulated by the environment they're in) , mammals (humans are mammals, in case you've forgotten) and birds (not mammals, in case you've forgotten) need their body temperature to stay at a certain level in order to survive. Too cold (hypothermia) or too hot (hyperthermia) and things go awry. Sometimes they get bad, sometimes they don't.
Let me explain.
Say you have your character trudging valiantly through frozen tundra. They're not properly dressed and their teeth are chattering from the cold and they are wandering around delirious.
Yeah, you might want to look to that. You see, teeth chattering and shivering stops after a certain degree of hypothermia. If your character is cold enough that they're shivering and their teeth are chattering, they're not, in reality, cold enough to be delirious. They're very cold and, while miserable, still in possession of their mental faculties, though they may not be as sharp as when they're not butt-cold. Those mental faculties might only be "fuck it's cold holy fuck oh my god shit shit shit it's freezing out here!" but their brain is still functioning. Delirium usually only occurs as hypothermia gets worse. Your mileage may vary.
Now, how cold are we talking about? Well, here are some numbers for you, directly from Wikipedia:
Normal human body temperature generally runs somewhere between 97.7–99.5 °F (36.5–37.5 °C) [Note – some guidelines increase this to 94–100 °F (34.4–37.8 °C) because again, your mileage may vary]. For example, my own personal temp runs somewhere around 97.6°F (36.4°C), so when I start getting chills/"running a temp" of 99°F (37.2°C), I have a fever. Why? Because my internal body temperature has gone up by two degrees, and that's at the threshold of "low-grade fever."
It's when things outside your normal happen (your homeostasis is disrupted) that stuff starts getting weird. Now, were my internal body temperature affected by those two degrees in the opposite direction, I'd be heading toward hypothermia. Again, I run about 97.6°F (36.4°C), so two degrees would put me at 95.6°F (35.5°C). Now, remember:
Hypothermia – temperature lower than 95.0°F (35.0°C).
Hypothermia is basically fancy medical speak for "the body can't warm itself faster than it's being chilled." (Remember that "homeostasis" thing? Yeah. The "stasis" part is being fucked up.) Warmth takes a lot of internal work, and when things outside get too much for the inside to keep up with (like, say, your wandering charrie out there in the cold) its grip on homeostasis starts to slip. By that reckoning, lowering my normal temperature by just two degrees puts me in the early stages of hypothermia.
What are those signs and symptoms?
(Note: "signs" are things that can be seen by others, while "symptoms" are things that are felt by the person affected.)
Signs of mild hypothermia may include shivering, cold to the touch, teeth chattering and so on. Obvious signs that someone is cold. Symptoms may include things like increased blood pressure, heart rate and respirations (this is the body working harder to warm itself – the heart beats faster and harder to get more blood out to the cold bits, and so on). There might be a bit of confusion mentally as well, but that's getting down into the more moderate version.
Moderate signs include more violent shivering, slurred speech, slow movement, stumbling, obvious coordination issues, clear confusion/disorientation, and pallor, while lips, toes, fingers, and ears take on a bluish tint. People in this stage can get really pissy too ("combative"), because hey…wouldn't you be pissed off if you were cold and everyone was in your face and you didn't know why?
Severe hypothermia (we're talking 82 °F [28 °C]) is when the person can barely speak, move, or think. Any skin exposed to the cold is blue and looks swollen, walking is all but impossible, and if they have any kind of mental ability at all, they do weird shit like try and hide in small spaces and take off their clothes. (The "getting naked" thing is really common in severe hypothermia, and is called "paradoxical undressing." You'd think when you're cold you'd want more clothes on, but for some reason, something short-circuits and your brain confuses cold with hot and you start getting naked, exposing your body MORE to the cold, so…yeah. That's why it's called "paradoxical" – because it makes no damned sense.) The thing about severe hypothermia is that it's tough to get back from. Severe hypothermia is what we call "freezing to death." No, really. I mean it. Your core temp dips below 85 °F (29.4°C), that's a long trip to make back. I know ten degrees doesn't sound like a whole lot, but really…in the grand scheme of things it is for homeostatic creatures.
Temperature regulation is critical for our species. When it's out of whack for whatever reason, it gets bad. Too hot is just as bad as too cold. Too hot in the fancy medical speak is called "hyperthermia." (See how fun that is? "Hypo" = low/less/below/under/beneath/down, "hyper" = high/more/excessive/above/beyond – you get it)
Hyperthermia is when body temperature is above 99.5–100.9 °F (37.5–38.3 °C) [Note: hyperthermia is different than fever, which is called "pyrexia." The difference is the cause of the temperature change. Fever is an internal change in temperature while hyperthermia is outside temps elevating it, like heat stroke.]. Hyperthermia is the exact opposite of hypothermia in that the body absorbs more heat than it can dissipate (instead of more cold than it can deal with).
Ever had heat stroke/heat exhaustion? Congratulations – you've experienced hyperthermia. (Some drugs can do this too, as can certain hormonal/medical conditions, but we're not going to get into that.)
Signs of hyperthermia include redness, flushing, hot dry skin (no sweating), nausea, vomiting, and headaches. Maybe some dizziness and fainting if the affected person gets up or is moved too quickly.
In cases of severe hyperthermia, it might seem like the person is drunk off their ass. They're slow to respond, confused when they do, are aggressive or grouchy, maybe even hostile. Don't worry – it's just the heat affecting their brain. Literally. This is a bad, bad situation. They need to be rehydrated and cooled down before their brain cooks itself to death (and the brain is a sensitive organ). If they fall unconscious, it may be too late.
Now I'm not going to get into treatment for these things now. That's another post in itself and this thing is already really long. Let's talk a little about fever then we'll call it.
Loads of things can cause a fever – a lot of exercise in a hot room, eating certain things, wearing too many clothes (remember that "paradoxical undressing" thing? Yeah.), medications, infection, humidity…and lots, lots more. I could do a post itself on fever, but here's the gist:
Fever by the numbers-
Fever is a body temperature greater than 99.5–100.9 °F (37.5–38.3 °C). We've all had a fever. It's miserable, and while you're hot, you actually feel cold sometimes. This is because your body is trying hard to get rid of whatever it is that's screwing with your normal thermoregulation, be that a virus or bacteria or whatever, and since your temperature fluctuates, the constant change makes you feel hot, then cold, and so on.
A little fever won't hurt you. In most cases, fevers are actually good, because they're working on your side to get things (your thermoregulation) back to normal (homeostasis). It's when fevers get out of hand that they become a problem.
Hyperpyrexia (excessive fever) is when the body temperature is greater than 104–106.7 °F (40.0–41.5 °C). This is getting into the "brain damage" area. Temps this high can cause seizures (usually in children but not exclusively) and even death if they're not dealt with immediately.
So, if you have your character trudging through a hot desert (or even just a hot sunny day in the city, where all that heat is reflected off tall buildings and so on) without any water for hours, they're going to be pretty parched if they're not going to suffer the effects of heat stroke/exhaustion. (Also, side note – you don't want to rehydrate them too quickly or they'll just vomit it back up which just adds to the "liquid loss" issue. Further, your character can't sweat if they haven't had anything to drink to sweat out, so…yeah. Research, people!)
That concludes our discussion on temperature. Well, actually, this does:
Questions about medical issues with your writing? Leave them in the comments below and I'll get back to you as soon as I can. (THESE MUST APPLY TO FICTIONAL SITUATIONS ONLY. I AM NOT YOUR DOCTOR, NOR A SUBSTITUTE FOR ONE.)