Fevers, paracetamol, Rigors

#KYJ -Rigors ( Hot shivers )

in a recent paediatric course that I was teaching, a nurse asked me about rigors (pron: rye-gores)

A rigor is  the uncontrolled shivering that a person with extremely high temperature often exhibits. It seems counterintuitive that somebody's temperature is very high they should shiver, but when you stop and look at the pathophysiology that causes this shivering, then it makes a whole lot more sense.  So start with, let's look at how fever is produced. 

The hypothalamus deep in the middle of your brain has a mechanism in it that regulates body temperature. It is a thermostat that maintains normal body temperature between 36 and 38°C. Older texts site 36.5 to 37.5°C.  Let's not split here's what's just say if your temperature is elevated above 38 then you have a fever, also called pyrexia.

Fevers are induced when White blood cells called macrophages release pyrogenic chemicals, as they enfulf dead infected cells, bacteria and viral destruction.   These pyrogens stimulate the release of the inflammatory markers known as prostaglandins particularly prostaglandin E (PGE).

When PGE is released in inflammation, this instructs the hypothalamus to raise the thermostatically set temperature, hence, fever.  As long as macrophages and neutrophils are actively fighting infection, they will continue to release the pyrogen is the cause prostaglandins to be formed.  Fever is therefore your body's natural response to fighting infection and enhances the immune system's ability to do its job.

Now let's have a look at how rigors occur.  When the hypothalamus reacts to PGE by raising body temperature, it actively causes the body to generate heat. This occurs a number of ways.  Reduction in heat loss, by pulling away blood vessels from the surface of the skin- vasoconstriction.  If this alone is not effective enough to bring body temperature up to the new thermostat set temperature,  then the brain initiates shivering which generates more heat thus reaching the new set point sooner. 

Therefore recognising this is a normal response in infective conditions, should a patient be experiencing shivering while febrile, despite seeming counterintuitive, nurses should actually put blankets on the rigoring patient to assist the body to increase temperature in accordance with its immune initiated goal.

Now this doesn't always sit well with us, because for years doctors and nurses have been taught to actively try and reduce temps. So putting a blanket on a febrile shivering person seems so silly, but when we grasp the concept that fever should be facilitated not inhibited, then we recognise that it makes for well informed care.  This issue of whether a fever should be treated or not is one that polarises nurses, doctors and parents. If you are game, you can view my thoughts on this here https://m.facebook.com/Ect4Health/posts/314445358696672

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For now, I hope that you have a greater understanding of rigors and how they occur. 

#KYJ - Febrile Convulsion. The myths vs the truths.

Over the years, few of our #knowingyourjargon topics have sparked as much interest as fever and its treatment. Fever in children seems to be a cesspool for cultivation of strong opinions in nurses.  Well boy, are you gonna hate this post.

If you have experienced caring for a child with febrile convulsion, you will probably remember the fear, trepidation and shear anxiety in the eyes of the parents of that child at the time.  In this post we explore this explosive onset presentation and dispel a few myths. 

Myth 1

Febrile convulsion is caused by high fever in children.

Truth: Febrile convulsion manifests when a temperature in a child aged 6 months- 3 years (rarely up to 6 years), changes rapidly.  It relates to the speed of fluctuation not the height of a temp.  A child with a temp of 41.6 is no more likely to fit than a child with a temp of 38.6.

Additionally, many febrile convulsions are induced during the rapid drop in temp seen post tepid sponging, and administration of antipyretic medication... Yes the ones on TV ads claiming "nothing works faster for pain and fever". Those ads are telling the truth, they cause RAPID drop in temperature.   These drugs prevent the formation of prostaglandins which are those "healing" thermogenic chemicals released during infection and inflammation.  

Myth 2

Febrile convulsion is dangerous.

Truth: a classic (or simple) febrile convulsion is one that follows three rules:

1- Short lived < 15 mins (92% less than 5 mins duration).

2- Convulsion onset is inside 24 hours from the onset of fever illness

3- Child will have only 1 convulsion during the illness.

The febrile convulsion that does not follow these rules is considered complex, and therefore sinister and  neurologically suspect.

Febrile convulsions do not harm the child and do not cause brain damage.  Whilst they are frightening to all who witness them, the hypoxic brain injuries associated with other convulsions and states of status epilepticus, are just not seen in children experiencing febrile convulsions. 

It is therefore safe to allow a febrile convulsion to ride itself out. It is not an emergency.

Myth 3

No antipyretic medication reduces the risk of febrile convulsion.

Truth:  antipyretic drugs (Ibuprofen and paracetamol) have been extensively studied for their prophylactic effects and found to be dismally ineffective.  In fact this is not new. It is a fact we've known since 1995, and was first proposed before many of our readers were born (pre 70s).

There is an interesting claim that they may even cause a convulsion.

Two mechanisms that induce fits.

Think about what neutrophils and macrophages are doing here.  Releasing chemicals to instruct the hypothalamus to raid the temperature. If paracetamol or ibuprofen is given and inhibits the prostaglandin message, more and more pyrogenic chemicals are being released by frustrated WBCs.  Now the antipyretic drug starts to wear off, massive amounts of pyrogenic chemicals released by WBCs now induce a burst of fever inducing prostaglandins, and the temp rapidly shoots up. 

The second mechanism is seen when a dose is given to a febrile child. The antipyretic shuts down prostaglandin production, resulting in a rapid fall of the fever. This in turn can induce the convulsion as they are caused by rapid fluctuation in temperature.

Myth 4

Febrile convulsions must be stopped.

Truth: they just don't.

While it is distressing to stand idle and do nothing, the only real benefit of stopping a febrile seizure is to alleviate the anxiety of the onlooker. So let's say you have a protocol or a mandate to treat, let's look at the standard management for convulsions.  Jurisdictions differ in their approach but always use one of two benzodiazepine drugs. Both are given mucosally, an IV cannula is not needed.

Midazolam is the favourite this month. Given intra-nasally via a mucosal atomisation device (MAD) pictured, the dose is 0.5mg/kg up to max 5mg.

It is a strong short acting sedative that may cause profound ALOC postictally (after the fit stops).  Therefore, lateral position, airway management, +/- oxygen if the kid's sats are below 95%

The other drug is Midazolam's older cousin, Diazepam.  This is usually given PR- low rectal.  10mg seems to be standard. Don't be pushing that stuff too high or it won't work!!  As a drug is administered low in the rectum it absorbed into systemic blood vessels and exerts immediate effect.  In fitting, this is desirable. If you ran it right up high in the rectum, the blood vessels drain first into the liver where diazepam is almost completely destroyed (read up on Hepatic First Pass).

Personally, I'm a fan of Midazolam, but that said, there is no evidence that a simple febrile convulsion needs to be stopped, and the irony here is that this family of drugs are also called anxiolytics, which is true when you think of the parents and nurses anxiety levels after the fit stops. 

Summary:

Febrile convulsions are caused by Rapid fluctuation of temp, not height of fever.

They are rarely harmful or even need to be stopped.

We have known for at least 20 years that antipyretic medications are not preventative.

More reading on this RCH site.

http://www.rch.org.au/kidsinfo/fact_sheets/Febrile_Convulsions/