Hi everyone, Jessica here, and welcome to CritIC.
Elevated body temperature can have detrimental effects on the body, so it should be regarded
as an alarm symptom for further investigation.
This video covers a structural approach to hyperthermia.
For simplicity, I’m excluding fever.
Don’t forget to check out my other video on hyperthermia in which we cover the definition,
why it’s dangerous and what you should do.
Now let’s go.
Hyperthermia can cause life threatening multi organ failure, so it’s vital to try and
figure out the cause.
In this video I’m providing you a structural overview that’s helped me remember the causes
of hyperthermia.
As mentioned in my previous video, you could definitely make the argument that there shouldn’t
be a distinction between fever and hyperthermia, based on both pathophysiology as well as the
fact that it’s difficult to differentiate between the two in clinical practice.
However, since I’m trying to convey an easy overview for you all, I’ve chosen to use
the classical definitions of fever and hyperthermia.
But you’ll find overlap.
Check out my One Critical Minute video for the definitions.
Causes of hyperthermia can be subdivided into 4 main categories:
drug induced,
environmental,
endocrine
and neurogenic.
Let’s start backwards.
Neurogenic causes of hyperthermia are due to damage to your hypothalamus, i.e. your
thermostat.
This can be seen in brain trauma, ischemic or hemorrhagic stroke,
or an increase in intracranial pressure
Endocrine disorders that cause hyperthermia are rare, and they don’t necessarily cause hyperthermia either.
Examples are thyrotoxicosis aka thyroid storm, pheochromocytoma and Addison’s.
Other symptoms will help you in figuring out these diagnoses: tachyarrhytmias like atrial
fibrillation in thyroid storm, severe hypertension in pheochromocytoma attacks, and the triad
of hypotension, hyponatremia and hyperkalemia in Addison’s.
To name a few.
Environmental hyperthermia can be split into exogenous warming
(like in heat stroke, when outside temperature is high)
and endogenous warming, caused by extreme sports with inadequate cooling.
Usually it’s a combination of both:
for instance, running a marathon on a hot sunny day
or doing Crossfit in a gym with inadequate ventilation.
love Crossfit btw ;)
Another important cause of endogenous warming is epilepsy.
Drug induced hyperthermia can be subdivided into 3 categories:
drug hypersensitivity, altered thermal regulation, and idiosyncratic drug reactions.
Let’s focus on these a bit more.
Drug induced hyperthermia caused by a drug hypersensitivity reaction, is actually considered
fever as it is an inflammatory response to a drug.
Drug hypersensitivity reactions are classified by the Coombs and Gell allergy types, one
through four.
I plan on making a separate video on drug hypersensitivity, so we won’t be going into
this too deeply right now.
For now, it’s important to remember that it can occur with just about any drug, especially
antibiotics.
If a hypersensitivity reaction occurs, your main action is to discontinue the drug and
provide supportive care.
In rare cases, drug hypersensitivity causes multi organ failure.
Examples are type IV reactions like TEN and DRESS.
Something for another video.
The second category of drug related hyperthermia are due to altered thermoregulation.
Examples are anticholinergic agents (which disturb hypothalamic function) and sympathomimetics
(which not only disturb hypothalamic function, but also cause secondary heat production
due to increased muscle activity).
The third category of drug related hyperthermia are the idiosyncratic drug reactions.
Idiosyncratic drug reactions are unpredictable, bizarre drug reactions, that can occur irrespective
of the given dose.
Notable ones that cause hyperthermia are the neuroleptic malignant syndrome, the serotonin
syndrome and what we call malignant hyperthermia.
Malignant hyperthermia occurs in response to general anesthesia
in patients with a rare autosomal dominant gene defect.
If you’re in anesthesia, it’s vital that you know about this syndrome.
An interesting article linked in the description.
Serotonin syndrome (SS) is a group of symptoms including hyperthermia, agitation and hyperreflexia,
with varying severity, but could be life-threatening.
It is caused by serotonergic agents, like SSRI antidepressants.
Treatment consists of discontinuation of the drug and supportive measures.
Symptoms then usually resolve within 24 hours.
The serotonin antagonist cyproheptadine can be considered in severe cases.
Neuroleptic malignant syndrome (NMS) is a life-threatening condition associated with
neuroleptics like haloperidol and risperidone, or the withdrawal of dopamine agents (i.e.
anti-Parkinson agents).
The pathophysiology is unknown, but probably has something to do with the blockage of dopamine.
It develops in a few days after exposure.
It is considered a medical emergency, and most patients require ICU admission.
Stop the neuroleptic, start cooling and rehydration and consider dantrolene or bromocriptine.
Now if you’re attending a patient that presents with a toxidrome, and he or she has hyperthermia,
it’s your job to differentiate between these causes.
Take a look at this table and notice the similarities and differences.
Vital signs won’t help you.
So how to go about distinguishing them?
Of course, a decent history will help you greatly.
I then start out by checking muscle tone.
If it’s normal, it’s either anticholinergic or sympathomimetic.
Note that sometimes it’s really hard to tell, especially if your patient is agitated.
To distinguish between anticholinergic and sympathomimetic, check the skin and mucosa.
Dry means anticholinergic.
I have a few videos on these toxidromes in which we go through assessment, complications
and treatment!
Check them out!
If there’s increased muscle tone, check reflexes and mental status.
Depressed means NMS, increased means SS.
Go back to the patient’s history and list of medication to see if the onset corresponds
with when the medication was started, or the dose was upped.
In summary.
When your patient presents with hyperthermia, beware of possible multi organ failure, go
through your ABC’s and start cooling.
When figuring out the cause, get a history to figure out if it’s drug related, environmental,
endocrine or neurogenic.
If it’s drug related, follow the mentioned steps to figure out the cause, discontinue
the drug and start appropriate treatment.
Let me know what you think about this video.
If you liked it, give it a thumbs up.
Thanks!