Friday, 3 March 2017

Why has no one told me this before? Confirmation bias - It lies to you. It lies to everyone. What has it been telling you about children? (Part 1)

Recently, after I had explained why something was a medical myth, a colleague in Primary Care looked at me and with genuine exasperation said, "Why has no one told me this before?"

Good question.  The answer to this is complicated.  A lot of the time there is a big 'Emperor's New Clothes' factor.  Declaring a myth to be untrue requires someone to burst the bubble and it is not always the case that someone is listening or that anyone wants to change their belief.

Myths start for various reasons but only persist if they are fed.  For example, very few people actually believe in the existence of fairies.   Seeing a fairy or hearing from someone who claimed to see one might change that.   People do however believe that mice like cheese without any good evidence to support this.  Where does this belief come from?  Surely we can't all have taken Tom and Jerry cartoons at face value?  Since there was never any reason to doubt what we were told we continued to believe it. Well, it turns out that, whatever the basis for the belief, it is wrong when tested scientifically (Yes, this has been researched and published!).

The best ingredients for a myth are plausibility and confirmation.  Take the old chestnut about not being allowed to use adrenaline with anaesthetic in fingers as an example.  This myth originated when lidocaine and adrenaline were commonly mixed with various things to aid anaesthesia and asepsis.  The mix often contained cocaine, procaine and boric acid.  When skin necrosis developed in fingers, the cause was not isolated, but the idea that a vasoconstrictor (adrenaline) was the cause was credible.  In fact, the other ingredients were probably to blame.  Thus a myth  has persisted for roughly a century was created by a plausible theory and repeated episodes which seemed to confirm this theory. (1)

Confirmation bias comes in several forms.  It affects how we search for, interpret and retain information.  They have been responsible for misleading us about quite a few things in paediatics.  There are so many, in fact, that it would be ambitious to put them all in a single post.  Instead I will divide them roughly into two groups - those where we have been misled about cause and those where we are misled about effect.

  • We tend to consider what the cause of something is when we witness an event.  
  • We concentrate on an effect when we think we can influence events.

For now, I am going to run through some examples of presumed cause.  Lets start with the things that you may have been told are caused by something else, but probably are not.  It works like this:

Of course sometimes, the presumed cause is real.  We have confirmation bias for a reason and in most cases it is teaching us, not lying to us.  Assumption has a bad name for itself, but is a necessary part of how we work and learn.
(No disrespect to Mrs. Sullivan, who taught me that to assume makes and ass of you and me.  Mrs. Sullivan was an English teacher and the spelling mnemonic is valid even if the statement is completely wrong in the context of exploratory learning.)

In certain circumstances, the reality is very different from our assumptions.  This is usually due to a factor that is not as obvious as the two that we have associated.

There are several examples of this below.  The one that often surprises many people is finding out that it is a fallacy that fever causes febrile convulsions.  I know, right?  I mean it's in the name and everything!  It makes sense that fever causes febrile convulsions since a child develops a fever and then has a convulsion.  We even see a correlation between febrile convulsion and fever that comes on particularly quickly (or so we think).

The only problem is that the evidence goes against this being true.  When children are treated for their fever, it seems that they have the same number of fits.  (2) So what is the cause of the fits?  Probably badness.  Badness is the stuff that infections make which causes the fever, the flu symptoms and all that.  You know, chemicals and stuff.  So even when we treat the symptoms of the infection, badness still causes the seizure to occur.  We can't get rid of viral badness.  In most cases we just make children feel better until they make themselves well.

How does this change our practice?  When I found this out, it completely changed my approach to children who had suffered a febrile seizure.  I no longer worry that treatment needs to be focused on the fever rather than the child's wellness.  Most importantly, I now tell parents that the seizure was not preventable.  Often, the parent blames themselves for failing to treat the fever adequately.  They need to know that this convulsion was not their fault.

Next up is the apparent epidemic of allergy to amoxicillin.
We have to work this one backwards from the evidence.  Approximately 95% of children who have a label of amoxicillin allergy have no allergy when tested or challenged. (3) The explanation for this poor correlation is that children of a certain age frequntly develop a rash (which is often urticarial) while ill with a virus.  Viral and bacterial infections are difficult to tell apart, so it is not uncommon for a child to be given antibiotics while unwell with a viral illness.  When a culprit is sought for the rash, the antibiotics may be blamed, though the reality was that the virus caused it.

Finding this out completely changed my practice.  By careful case selection, I take every opportunity to undiagnose penicillin allergy.

Next up: another much maligned medicine - Ibuprofen.   Ibuprofen is often avoided in children who have history of wheeze.  I suspect that this is one of the biggest cases of (wrongly) presumed cause currently in paediatric practice.  You may have been told that ibuprofen causes wheeze or that ibuprofen should be avoided in children with a history of wheeze.  Well, it turns out that this is another myth that has persists despite being disproved.

Once again, the association in space and time of the medicine and the symptoms leads to a very rational fear that it is the ibuprofen causing the wheeze.  When large groups are studied, it seems that Ibuprofen may even be protective against wheeze. (4)  I'll just leave that one with you for a minute...

So after that bomb shell, something a little more palatable but still interesting.  Growing pains are not caused by (wait for it........) growing.  In fact no one knows what causes children to have growing pains.
Feel free to file this under 'how does that change my practice?'  I just think that it is interesting that we feel the need to have an explanation for a symptom which has no known cause and no effective treatment - a bit like colic really!

Next up is something a bit more meaty.  Based on the sessions that I do for GPs here and there, I would approximate that roughly three quarters of primary care clinicians are aware that there is a concern about using ibuprofen for children with chickenpox.  I also know that the basis for this concern is poorly understood.

The truth is that this concern was raised based on a cluster of cases of children who developed severe complications of secondary infection about 20 years ago (5).  No causal link has ever been convincingly shown and the fact that huge numbers of children continue to have ibuprofen in this context makes me think that more robust evidence would have emerged if there was genuine cause and effect.

Invasive streptococcal infection during varicella infection is something that all clinicians should know about.  It is also true that most children who have chickenpox are not very unwell and so paracetamol should be all that is needed.

So why does this matter?  It matters when someone is blamed for something based on poor evidence.  So, let's be clear.  The Emperor appears to be naked, but if anyone else can see that he's got clothes on, I am prepared to be convinced.

Edward Snelson
Non-steroidal guardian of the year 2014-2016

Disclaimer- I would never use any of the treatments listed above.  For many years now I have only used fairy magic to treat my patients and any prescribed medication is a pretence.  No one can prove to me that fairies don't exist. 

  1. Bradon et al, Do Not Use Epinephrine in Digital Blocks: Myth or Truth?, Plastic & Reconstructive Surgery, February 2001
  2. A Sahib El-Radhi, W Barry, Do antipyretics prevent febrile convulsions?, ADC, Volume 88, Issue 7, 2003
  3. Caubet JC et al., The role of penicillin in benign skin rashes in childhood: a prospective study based on drug rechallenge, J Allergy Clin Immunol. 2011 Jan;127(1):218-22.
  4. Kanabar et al., A review of ibuprofen and acetaminophen use in febrile children and the occurrence of asthma-related symptoms, Clinical Therapeutics, Volume 29, Issue 12, December 2007, Pages 2716-2723
  5. Zerr DM. et al., A case-control study of necrotizing fasciitis during primary varicella, Pediatrics. 1999 Apr;103(4 Pt 1):783-90.

Thursday, 9 February 2017

Dates for your diary – Constipation in Children

If (like me) you are still sorting out your 2017 diary, I have some important dates for you to add.  They all relate to that child who you are about to see with constipation.

Constipation is very common in children over the age of one year old, being prevalent in around 20% of children.  It is responsible for many presentations to GPs, Emergency Departments and other unscheduled care providers.  Sometimes the family knows that constipation is the problem but often they are perplexed by symptoms that they do not necessarily associate with constipation.

By far the most common perplexing symptom of constipation is abdominal pain.  This pain can be acute, chronic or both.  It can be severe or mild enough that the child does not articulate their discomfort to the parents.

So, back to the diary: this child who is presenting with what turns out to have constipation has a timeline.  Assuming that they presenting for the first time, now in February 2017, these are the relevant dates:

August 2016

This is the time that the child began to become constipated.  It is often the case that it seems that the problem has been there for a much shorter period.  When the child eventually comes to see you, the parents may have been aware of the abdominal pain for a few days or hours, but it takes a long time to become constipated to the point that symptoms occur.  Think of it like a massive ship.  It takes a long time for one of these to come to a full stop.  Likewise, it takes months for bowels to reach the point that they are loaded and unable to function, which is the point at which they will present to you.

February 2017

The parents will present now because they recognise a problem.  This maybe abdominal pain or perhaps they have seen blood on the toilet paper.  Often, there will be a reluctance to accept that constipation is the cause of these things.  This is for a variety of reasons.

Parents are unlikely to know exactly what a child's bowel habit is.  Asking if the child opens their bowels and if this is normal is unlikely to unmask constipation as the villain here.  Instead it is important to ask specific questions.

  • Does the child strain to pass stool?
  • Is it painful for the child to open their bowels?
  • Is there ever blood on the stools or toilet paper?
  • What do the stools look like?

If they identify type 1, 2 or 3 stool from the Bristol chart, this indicates constipation.  If the child is passing only liquid stools, this may be overflow due to severe constipation.

If the problem is most likely constipation, it is also very probable that it is idiopathic constipation.  In the absence of red flags, it is usually appropriate to treat without any need for investigation.

The best treatment is macrogol laxatives (1) in increasing doses to achieve easy passage of formed stools.  It may be necessary to see this child on a few occasions to get the dose of laxative perfect.  The aim is to have the child passing soft, well formed stools easily.

There is a lot to explain in the first consultation.  Parents and children often disbelieve that constipation may be causing the child's symptoms.  I find that pictures help.

Pictures taken from The Essential Handbook of Common Paediatric Cases and used with permission from BPP learning media. (2)

March 2017

By now the symptoms of idiopathic constipation should be improving or possibly gone.  This is an important visit because there are two essential outcomes for this child.

1 - Do not stop the macrogol laxatives.  It takes a long time to become so constipated that you will go to see a doctor.  By the time children present, they have a stretched, weak and numb bowel.  If you stop their laxative now it is too soon.  NICE recommends 4-6 months of treatment in order to restore the shape, strength and sensation to the colon before the child is weaned off medication.

2 - Reinforce the message about the importance of diet and toileting.  Of course you covered this when you first started the medication, but for ten different reasons, it is unlikely that this message has been fully heard and understood.

August 2017

This may seem like a long time away, but this is when it might be time to reduce and stop the laxatives.  If the child has been taking their macrogol for about six months, then the shape, strength and sensation should have returned.  This gives them the best possible chance of being constipation free.  Diet and lifestyle are just as important at this stage as when they were first diagnosed.  Treating and preventing constipation is a lot of hard work  but the results are worth it.

Edward Snelson
Specialist Spitilomancer

Please note that babies who struggle to pass stool are often  experiencing a normal physiological phenomenon called dyschasia.

  1. Constipation in children and young people: diagnosis and management, NICE CG99
  2. The Essential Clinical Handbook for Common Paediatric Cases: A Practical Guide to Assessing Children in General Practice, the Paediatric Assessment Unit and the Emergency Department, BPP Learning Media

Wednesday, 25 January 2017

The Well Covered Wheezer

Guidelines almost always dedicate themselves to 'what to look out for'- the red fags and risk factors.  Often, we go to a guideline in order to learn about a condition, only to find that we should be afraid, very afraid.  I think that the tendency for the glass-half-empty factor in guidelines is almost certainly due to the understandable desire to err on the side of caution.  When you are writing a guideline, you are very aware that if (when) a patient has a bad outcome, the guideline's recommendations will be critiqued.

However, I don't want my doctor to intentionally err at all. To be honest, the error being on the side of caution is very little consolation.  Unnecessary tests, treatments, referrals and admissions are not what I want.  I want my clinician to be thoughtful and careful, but courageous, not risk averse.   I believe  that calculated risk is a necessary part of practicing medicine well, and so struggle with guidelines that give us the impression that we have to follow a certain pathway even when our instinct tells us that this is not needed.

Of course, I know that many of you will now be thinking, “Guidelines are just guidelines.  You don’t have to follow them.”  While this is of course a true statement, try telling this to a clinician who has been to court regarding an adverse outcome.

I don't want to return to an era bereft of guidelines.  That was no fun at all.  Someone else knew what you were supposed to do, most of the time.  It was your job to guess what was expected of you and then find out afterwards if you were right, rather that to be told beforehand.  However, we need to be aware of the negative effects of guidelines, so that we can protect against these.  (1,2)

I do feel that the guideline era has taken some of what used to be taught and allowed this to drift into mythology.  So, in the interest of history, I thought that I would explore what the guidelines often miss out – the signs that are reassuring.  When marking some assignments for the Primary Care Paediatrics course at Sheffield Hallam University, I was delighted to find the oldest reference that I have ever seen in one of these submissions.

Cassell’s Household Guide to Domestic Medicine (1886) - “…on the minutest air-tubes the cells of the lungs are placed… inflammation of these tubes is one of the most fatal diseases in our climate…The child is quickly bereft of its usual liveliness… the breathing is quick and the nostrils expand more or less… All these symptoms are worse if they occur in delicate children…”(3)

The first thing that struck me about this was that in Victorian Britain, the pathophysiology of bronchiolitis was already known.  The second was that they recognised that scrawny babies with bronchiolitis were the ones to worry about.  This brings me onto the well covered wheezer.
In the days before guidelines, I learned paediatrics by trial and error with a degree of question and answer.

Me: “This child is very wheezy.”
Consultant:  “They’ll be fine.  They’re a fat, happy wheezer.”
Me: “So because they’re a bonnie baby and smiling, they’ll be fine?”
Consultant: “Pretty much.”

I don’t know of any research demonstrating the protective benefits of an extra pound of subcutaneous fat when suffering with bronchiolitis.  What I can tell you is that 20 years on, I’ve never had cause to feel misled by this conversation.  That is partly because I leaned the difference between red flags and those that were more of a blood orange colour.

I would say that it is only the 'significant tachypnoea or recession' which could be negated by other reassuring factors such as being well covered and cheerful.  I also think that this is probably self fulfilling: children with the other red flags are too significantly affected to actually have any reassuring features.

What is also interesting is that, in a straw poll of ten junior doctors, none had heard the term ‘fat happy wheezer.’  This is not down to modernity either.  None of the doctors in question had heard it said that habitus was worth considering when assessing a child with bronchiolitis.  I put this down to an overemphasis on red flags and risk factors, without justice being given to reassuring signs.

So, I am going to appeal to two groups of clinicians to help restore balance to The Force:

Firstly – all you experienced, common sense clinicians, please comment below and let me know what other things are reassuring signs which might be unproven but tell you not to be so worried.

Secondly – all you academics, please research these things and get us the evidence to back up what we all know to be true.  After all, this stuff has been known for 130 years now. It’s time we proved it.

Tuesday, 3 January 2017

Your New Year's Resolution - Undiagnose a Child This Year

If you’re wondering what to do for your New Year’s resolution, don’t give something up or join a gym.  Neither will work out anyway.  This year, do something truly worthwhile - promise yourself that you will undiagnose a child or three.

Paediatrics is particularly prone to the pitfalls of overdiagnosis and overtreatment.  Although this is a problem, the reasons for overdiagnosis are actually good ones:

When there are no good tests available to tell between two possibilities, we sometimes give a therapeutic trial to help answer the question.  That is a strategy which will lead to misdiagnosis if symptoms improve despite our treatment rather than because of it.

With therapeutic trials, it is often best to challenge the assumption that it was the treatment that worked.   The two best examples that I can think of are childhood asthma and cow’s milk protein allergy in infants.

Let me give you a case to illustrate what I mean:

A 3 month old has been treated unsuccessfully for symptoms of gastro-oesophageal reflux disease (GORD).  A clinician suspects non-IgE Cow’s Milk Protein Allergy (CMPA) because first and second line treatment for GORD has been unsuccessful and because they notice that the baby has quite significant eczema.  (Click here to see a guide to diagnosing feeding problems in this age group)  The clinician decides to trial an extensively hydrolysed feed.  Over the next few weeks, the child’s symptoms of being unsettled and bringing back feeds improve considerably.  The eczema is responding to topical treatment.

In this situation, it is easy to assume that the change of milk was what made the difference.  Often, this is simply confirmation bias.  Colic, reflux and other symptoms of infancy have a tendency to self-resolve.  Of course the treatment may have been what worked but at this point in time, we genuinely have no idea.

This is the time to stop the hydrolysed formula and reintroduce a standard formula.  (Only do this for Non-IgE CMPA.  IgE CMPA is the kind that has urticaria and wheeze etc.  The children with this type of allergy need to be referred to an allergoligist.)   If the original symptoms of being unsettled and vomiting lots return in the next couple of weeks, the diagnosis is now more robust.  If the child remains well despite a return to standard formula, you have undiagnosed a thing.  Marvellous.

The second clinical scenario is the 7 year old with a nuisance cough.  The cough has been there for somewhere around 2-3 months.   There are no associated symptoms such as wheeze or altered exercise tolerance, but the cough is waking the family up at night.  The chest is clear on examination.

So, what is the likely diagnosis?  Surprisingly, in research land, coughs like this turn out to be caused by pertussis infection more often than asthma or reflux disease. (1,2)  It seems that although the pertussis vaccination is successful, infection is still relatively common.  Instead of causing a more significant respiratory illness, what we see in vaccinated children is often just the cough that lasts 100 days.  There are other, similarly benign reasons for chronic cough in children.  Also, there are plenty of significant pathological causes of chronic cough that are not asthma.

Diagnosing ‘cough variant asthma’ is possibly the biggest reason for the current debate about overdiagnosis of asthma in children, fuelled by an article in the BJGP earlier this year. (3)   Many children in the UK are prescribed inhaled steroids for chronic cough symptoms.  If they get better, this is taken as evidence that they had asthma, but there are other possible reasons for this resolution of symptoms.  The evidence suggests that the most likely thing is that the cough has resolved with time rather than with treatment.

This is therefore another opportunity to undiagnose a thing.  As well as stopping inhaled steroids after (Snelson makes up a number quickly…) three months it is probably a good idea to get some sort of objective assessment before, during and after the therapeutic trial.  Peak flows are great if you can get the child to do these well.  In many cases a symptom score (4) is more achievable.  If the only complaint was cough, then a symptom diary is all that is required.

If when you stop the steroids, the child’s cough is still resolved, you have a winner.  Your New Year's resolution is fulfilled.  Of course, once you start, undiagnosing an become a bit addictive.  If you find it becomes a problem, why not join a gym instead?

Edward Snelson

Disclaimer: My New Year's resolution is to get a better disclaimer.

  1. Marchmont et al, Evaluation and Outcome of Young Children With Chronic Cough, Chest Journal, May 2006, Vol 129, No. 5
  2. Wang et al, Whooping cough in school age children presenting with persistent cough in UK primary care after introduction of the preschool pertussis booster vaccination: prospective cohort study, BMJ, 2014;348:g3668
  3. Looijmans-van den Akker et Al, Overdiagnosis of asthma in children in primary care: a retrospective analysis, BJGP, 1 March 2016
  4., Child Asthma Control Test

Monday, 19 December 2016

If you can't decide between turkey and goose... Pertussiolitis and other animals - when a child has noisy breathing

Recently I learned a good way to find the answer to a question.  It happened like this-

On a walk in Sheffield I saw this strange bird:

Unable to find this creature described in a ‘Birds of Britain’ book, I posted the picture to Facebook and commented that (to me) it looked like a cross between a turkey and a goose.  Most other Facebookers were similarly unfamiliar with the species but within a short period of time, I received a response from my niece who declared the bird to be a Muscovy duck.  After quickly confirming this to be true, I asked how she recognised this bird which is not native to the UK.  The response that came back was simply that she had searched the internet for "birds which look like a cross between a turkey and a goose". 


I had the chance to complete this lesson, for myself in a clinical context, shortly afterwards when faced with another unfamiliar animal, this time in the form of a baby with an ambiguous presentation.  The child had developed a cough and feeding difficulties and had now become wheezy.  Preemptively, my diagnostic centres had skipped forward to the disease that I thought I merely needed to confirm: bronchiolitis.   This mental process was interrupted by a cough from the child, and what a cough it was.  It went on and on and on…  At the end of the period of coughing, the child’s face was properly red. The mother informed me that more often than not a spectacular vomit followed these paroxysms of cough.

With the new possibility of whooping cough suggesting itself, I examined the child with a new mission: confirm findings that are consistent with pertussis infection.  I was therefore, properly annoyed to find a wheeze which I felt was more in keeping with bronchiolitis.  Faced with this puzzle and remembering my niece’s methods, I asked the internet and found that, while not a typical feature of pertussis infection, wheeze has been well described in a large number of cases of children with whooping cough. (1)

This case reminded that, as primary care clinicians, we don’t really diagnose infections- we diagnose syndromes.  Bronchiolitis, for example, is not RSV infection.  Bronchiolitis is a syndrome of wheeze, poor feeding and cough which can lead to severe respiratory distress, apnoea and feeding or respiratory failure.  RSV is one possible cause amongst many untreatable viruses.

Similarly, despite what I was once taught, croup is not caused by parainfluenza virus.  Any virus can cause the upper airway swelling that leads to barking cough, possibly stridor and varying degrees of respiratory distress.

Just to keep me on my toes, children seen to present from time to time with features of multiple syndromes.  The most common bedfellows are croup and viral induced wheeze.  When faced with a child who has a barking cough and a wheeze, one initially questions whether the noise is in fact a stridor (and rightly so).  If it is a wheeze, then it is a wheeze.  If the child has both croup and viral induced wheeze, ther is no point trying to limit the diagnosis.  Just get on and treat both.  It occasionally causes a bit of confusion if the child needs admission.  I think that some junior doctors take the referral of a child with the diagnosis of viral wheeze and croup together to be a sign of uncertainty, or perhaps dementia.

I would suggest that perhaps wheeze is not a feature of whooping cough but that it is possible for a baby to have bronchiolitis at the same time as whooping cough, both caused by pertussis infection.  It doesn't really matter though, since the cause of the infection is only of interest if it can be treated, or transmission prevented.

There are so many infectious causes of noisy breathing in children. Here is a simple guide to what’s what and what to do about it:

Many thanks to my niece for teaching me what the internet is for.

Edward Snelson

Disclaimer: I take full credit for inventing the use of evidence based medicine in the consulting room.

  1. Taylor Z.W. et al, Wheezing in children with pertussis associated with delayed pertussis diagnosis, Pediatr Infect Dis J. 2014 Apr;33(4):351-4.
Acknowledgement: This is a slightly different version of a post which I wrote for the Network Locum Blog earlier this year.

Wednesday, 7 December 2016

How to spot a made up number and what to do with it

Paediatrics is absolutely full of made up numbers - we rely on them every day.  If you think about it, many of the numbers that we have been given to work with are too conveniently rounded to be believable.  I don’t want to spoil the movie for you, but you have been lied to an awful lot.

The question is then. what do we do with the made up numbers?  Knowing where they come from is the key to the answer to that question.

Lie number 1 – For a baby, the normal milk intake is 150ml/kg/day

This one goes way back.  It actually comes from a number of fluid ounces per pound per feed which was a rough guide produced back in the bad old days.  The thing is that no-one has ever done a robust study finding out how much the average breast fed baby takes in 24hrs because there has been no good way of checking.  Not only is the number 150 a bit conveniently round and decimal, no one can tell you what the 5th and 95th centiles are. These facts would be essential for you know if a baby is taking an abnormal amount of feed.  The reality is that the mean (which this may or may not be) is not what we need to know in the first place if we are trying to assess whether feeds are too much or two little.

Luckily, you don’t need to know.  The best way to tell if the feed is enough is by the effect it has on the baby.  If it is too little, the baby won’t grow.  If it is too much the baby might exhibit signs of reflux disease due to overfeeding.

This brings us back to the question of what to do with a made up number.

Just because a number has never been validated by research doesn’t mean it’s not at all valid.  This particular number has been in use for decades now and is a useful landmark even if we don’t know which side of the truth it sits on.  The fact that it is accepted practice tells you that it has value - if it was frankly misleading, someone would have noticed.  The 150ml/kg/day number does at least tell us whether a child might be having too much or too little feed.  Knowing that you’re nowhere close to that figure is also useful.  For example, if a baby has faltering growth and is found to be taking 50ml/kg/day of milk, then lack calories would be a reasonable diagnosis.

Lie Number 2 – A normal heart rate between the ages of 0 and 1 is 110-160

For many years there have been three main lists of ‘normal values’ for physiological values in children.  We rely heavily on these as warning signs when it comes to recognising ill children.  Those reference ranges were all different for a reason – they were decided upon by experts rather than being based on definitive evidence.

Two published papers (1,2) have shown that the numbers in pooled population data conflict in places with the normal values in these reference ranges.  Notably however, the authors of these papers acknowledge that (I paraphrase) there is no such thing as a normal value when it comes to heart rate or other parameters in children.  There are just too many variables each of which can have a huge effect: sleep, activity, fear, pain, fever...  You get the idea.  Do we need to have normal values for a three year old who has just eaten an ice cream but is upset because a sibling has taken a toy off them?  I would love to have an app that takes into account variables like tiredness and temperature.  In the meantime, what I have is a lot of numbers that give me some idea of what normal might be, if only there was such a thing as normal in a child.

In many ways, the studies referenced show that consensus or expert opinion can be pretty good at coming up with the answers.  The correlation between the study findings and the made up numbers is remarkable.

I find it liberating to know that a heart rate can’t be treated as a piece of information out of context.  After all, we should always be looking at the child.  If their numbers are lying to you, hopefully their smile will tell you the truth.

Lie number 3 – a baby should lose no more than 10% of their birth weight in the first week of life

By now, you should be able to spot these numbers for what they are:

  • Made up
  • Still useful
  • Only helpful in context

It’s that simple.

The lies go on and on.  I couldn’t even begin to list the drug doses that are either plucked out of nowhere or at best based on some research where a number plucked from nowhere was shown to work.  Adrenaline for cardiac arrest is in the former group amazingly.  Fortunately for most drugs, we are protected by a wide therapeutic margin of error.

I like numbers.  Unfortunately children are themselves hugely variable and rarely normal.  I certainly wasn’t.

Edward Snelson
Chaos conspiricist

Disclaimer - If you can't trust numbers, what can you trust?  Certainly not me.


  1. O'Leary, F at al, Defining normal ranges and centiles for heart and respiratory rates in infants and children: a cross-sectional study of patients attending an Australian tertiary hospital paediatric emergency department, ADC, 2015
  2. Fleming et al, Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies, Lancet 2011;377:1011–18

Wednesday, 23 November 2016

Empirical Paediatrics – What is the best rehydration fluid for children with gastroenteritis?

When children have an uncomplicated gastroenteritis, dehydration is the enemy.  There are lots of things that we can give children to drink, but what is the best rehydration fluid to keep children out of hospital?

There are many things said about which fluid is best.  NICE recommends water or milk to maintainhydration but says to avoid fruit juice and carbonated drinks. (1)  In children who require rehydration they recommendoral rehydration solution (ORS).  In my previous post I listed 10 myths about gastroenteritis and used that to point out the NICE recommendations.  This advice conflicts with a study published in the JAMA (2) this year which showed that half strength apple juice was more likely to work than oral rehydration solution.

So, I’ve had another look at the basis of the NICE recommendation that we should “use ORS solution to rehydrate children” and the reason given is: “Although there were no clinical trials on the effectiveness of fluids other than ORS solution in the treatment of dehydration, the GDG considered that the composition of such fluids was generally inappropriate.  In dehydration due to gastroenteritis, both water and electrolyte replacement is essential, and non-ORS solution fluids do not usually contain appropriate constituents.  ORS solution was considered the appropriate fluid for oral rehydration.”

In other words, there was no evidence to support other fluids than ORS and there was reason to suspect that they are not ideal.  The trouble with two plus two is that it only equals four if there are no unknown variables.  The empirical approach dictates that instead of trying to figure out what should be true, we only believe what can be evidenced.  That removes the risk that there are unknown unknowns.  In the case of keeping a child hydrated, there is a big wildcard- the child.
One of the more interesting results of the apple juice vs oral rehydration fluid study was that the effect (half strength apple juice being more effective) was more pronounced in children over the age of 2 years.  I think that phenomenon is easily explained by two things:
  • Children develop the ability to choose for themselves
  • Oral rehydration fluid has a disgusting taste

When looking after children, we often have to choose between the treatment that is best on paper and the treatment that the child will take.  In this case, taste beats logic hands down.

So what do you do when your guideline tells you not to do something?  I would say that we need to recognise that while guidelines have strengths, they also have weaknesses.  NICE and other similar guidelines require a huge amount of searching through evidence, appraising applicability of the literature, and ultimately a decision to be made by people, with everything that entails.  What we get from that is a load of recommendations from people who have worked really hard to give us the best answers that they can come up with.   Now that there is evidence for apple juice, this will no doubt be considered when the guidelines are revised - a process that will take a very long time.

Even when a guideline is up to date, it is up to us to apply it to the child in front of us.  For example, where is the guideline for treating gastroenteritis in a child with autistic spectrum disorder?

Will flat cola be the next thing to be shown to be effective after all?  Who knows?!  What I do know is this: we now have an evidence base for a rehydration fluid that is palatable, readily available and doesn’t require a trip to the pharmacy or the doctor’s surgery.  That has got to be a win for de-medicalising and a victory for self-care.

What do you do if the child doesn’t like apple juice?  Don’t give them that then.  What is clear is that (within reason) the best rehydration fluid for a child is the one that they will take.

Edward Snelson
Eventual empiricist

Disclaimer - I was taught the theory of empricism by my daughter.  If this is all wrong, it's her fault.

  1. Diarrhoea and vomiting caused by gastroenteritis in under 5s: diagnosis and management, NICE CG84, Published date: April 2009
  2. Freedman, S et al, Effect of Dilute Apple Juice and Preferred Fluids vs Electrolyte Maintenance Solution on Treatment Failure Among Children With Mild Gastroenteritis, JAMA. 2016;315(18):1966-1974