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
Diagnosectomist
@sailordoctor

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

References:
  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. Asthma.com, 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". 

Boom.

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
Ornithopathologist
@sailordoctor

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


Reference:
  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
@sailordoctor

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


References

  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
@sailordoctor


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

References
  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



Thursday, 13 October 2016

Why bronchiolitis doesn't get better with inhalers and how understanding "why?" is better than "do that!"

There was interesting debate this week about using inhalers for bronchiolitis.  The interesting features included how heated it became (there was mild name calling and much "prove it" involved, rated PG) and how confident people were in expressing their views on social media about their differing clinical practice.  (Take it from me that you should be fairly sure of yourself before you put something out onto the interweb.)  To me what was most interesting was that the views, despite being polar opposites, where seen as fact.  I am going to assume that all involved want to practice the best possible medicine, but someone must be wrong mustn't they?

What do the guidelines say?  The American Academy of Pediatrics and the UK's National Institution of Clinical Excellence along with other institutions, have produced guidelines in the past few years, specifying that beta agonists and ipratopium should not be used, so why are such debates still happening?  I think that there are a few reasons.  One of these is that for medics, knowing what to do is not as powerful as knowing why, especially when it comes to changing practice.  For me, understanding a disease is much more effective as a learning process than being told, "This is the disease and this is the treatment."   I suppose it is because I already understood the reason why I was doing what I was doing (even if the understanding was flawed), so a diktat is not as powerful a persuader as a new and better understanding.


There is a perpetuated myth regarding beta-receptors and infants.  This myth comes from early studies that failed to find evidence of beta-receptors in infants.  Since then, (as early as 1987) research of better methodology (3) has proven that these receptors are there from birth.  The myth persists because (just as the news reports plenty of crises but not so many resolutions) we are often told things, but rarely does anyone untell us something.

Perversely, the beta-receptor folklore has done us no favours when it comes to trying to understand bronchiolitis and viral wheeze.  The uncertainty created by this myth makes clinicians think that a lack of beta receptors has caused the lack of response to salbutamol.  In fact, the child would respond just fine if only they had bronchospasm.

In bronchiolitis, there is no bronchospasm so salbutamol does not help.  In viral wheeze, ipratopium is a poor treatment and the old myth about ipratropium leads some to believe that ipratropium is the first line treatment for this age group when what they really need is plenty of salbutamol if they really do have bronchospasm.

When discussing the management of wheeze in infants, I often get the impression that people believe that bronchiolitis is just what you call viral wheeze in a child under the age of 12 months.  In fact this is not true.  Bronchiolitis is a separate entity, with different histopathology and a unique clinical pattern of illness.  There is a gradual unset of symptoms, peaking at day 3-4 and beginning to resolve at day 7-10.  Doesn't sound very spasmy does it?

Of course the confusion arises from the fact that both bronchiolitis and viral wheeze are caused by a viral illness.  They can both occur in a child around the age of 12 months old and they cause similar symptoms.  There is however a subtle but helpful difference in the way that they present.

The reason for this difference is a difference in mechanism.  While bronchiolitis and viral wheeze share a cause, the pathology is different because the effects on the airways are different.


I suppose that since it is unrealistic to think that all uncertainty can be removed, the question remains, what is the harm in trying a bronchodilator in all every case, just in case?  Here are a few possible reasons why it is going to make things worse if it isn't going to make things better:


It's always difficult when two illnesses have so much overlap, but there are genuinely good reasons to avoid unnecessary treatment for bronchiolitis.  Hopefully understanding why bronchodilators don't work helps the thinking clinicians to decide for themselves, rather than just being told what to do by guidelines.

Edward Snelson
Mytharchivist
@sailordoctor


Disclaimer:  I would like to express my appreciation to the children who allowed me to perform lung biopsies on them during their wheezy episodes.  Science thanks you.


References
  1. Clinical Practice Guideline: The Diagnosis, Management, and Prevention of Bronchiolitis, American Academy of Pediatrics, October 2014
  2. NG9 Bronchiolitis in children: diagnosis and management, NICE, June 2015
  3. A Prendiville et al., Airway responsiveness in wheezy infants: evidence for functional beta adrenergic receptors, Thorax. 1987 Feb; 42(2): 100–104.

Thursday, 29 September 2016

The Internet Has Ruined Everything (Easter Egg - Things You need to Know About Chickenpox)


Things were so much easier when life consisted of being told something by an authoritative figure, after which you could go on indefinitely, believing that fact to be true.  That is how most of medicine has been taught and learned.  The trouble is that much of what we are told is either untrue or unfounded.  Of course to ruin it all, there in now a way to check up on what you are told.  That has made life very difficult for anyone in a medical educational role.

Let me give a non-medical example to illustrate my point.  A few years ago, after watching the film Guardians of the Galaxy, I was commenting on the way that Vin Diesel's role as an animated character was a departure from his roots in gritty action thrillers.  My daughter politely told me that this was untrue, since he had played the title role in the rather brilliantly animated Iron Giant film (1999).  Since I am big and she was little, I felt it only reasonable to set my daughter straight, pointing out that said film was intelligent and Vin Diesel was a hard core meat head who at that stage had not yet begun his career as an actor in any meaningful way.

In my childhood, that would have been the end of the matter.  Faced with such an argument I would have accepted my wrongness or at least agreed to differ with said parent.  This is no longer how these things play out and I was confronted immediately by my wiki-error and proved wrong.

Imagine if we should start to do that with what we think we know about anything in medicine.  Take chickenpox for example: Let's explore some of the things that you might have been told about one of the most common childhood infections.

1. Chickenpox (varicella) is a benign, self limiting viral illness

While that is mostly true, Chickenpox has a surprisingly bad track record.  here are a few chickenpox stats that may surprise you:

  • Hospital admission rate of up to 6 per 1000 cases (2)
  • Mortality of 2-3 per 100,000 cases (1,2)
  • Risk of death four times higher in infants (2)
  • 70% of deaths occur in otherwise healthy cases (2)

What causes these admissions and deaths?  It turns out that chickenpox has an alarming number of potential complications.  The most common complication of chickenpox infection is secondary bacterial infection.  This can be the obvious culprit: stapphylococcus aureus.  However probably more commonly and certainly more significantly, group A streptococcal (GAS) infection is the real enemy.  Children with chickenpox are particularly prone to this infection which accounts for the majority of varicella associated deaths.


Other acute and serious complications include encephalitis and pneumonia.  The morbidity and mortality of all of these has been significantly reduced where varicella vaccination has been introduced.

2. You should not give Ibuprofen to children who have chickenpox

If you haven't come across this chestnut then I apologise for being the bearer of bad and rather confounding news.  There has been a controversy about ibuprofen and chickenpox for a long time.  Around the same time that Vin Diesel was voicing the Iron Giant (1999), there was a case controlled study published in which a significant number of children with chickenpox developed necrotising faciitis. (3)  For whatever reason, the authors suspected a link with ibuprofen use and indeed found an association.

This has led many to recommend that ibuprofen is not used as an antipyretic for children with chickenpox.  I believe that the case for this avoidance is based on flawed information.  Firstly, there is the confirmation bias of the original work.  Some of the cases in the study were the same cases that led the authors to ask the question: 'Is there a link?'  Secondly, although it was a case controlled study, the children in the control group had less fever.  Could that be a confounder when looking for an association with an antipyretic one wonders...  Indeed, at the time ibuprofen was a prescribed drug.  In many ways, you could say that the conclusion could easily have been 'Children with chickenpox who were sick enough to see a doctor had a ten times greater risk of developing necrotising faciitis.'  Finally, the association (if there was one) was mainly with ibuprofen being given after there were signs of invasive GAS infection.

The case for avoiding ibuprofen in children with chickenpox is far from convincing.  I certainly don't think that anyone should be accused of bad medicine if they have used ibuprofen for a child with uncomplicated chickenpox.

My advice is this:  Use paracetamol as first line treatment for fever in children with chickenpox.  If a second antipyetic is being considered, ask 'Why does this child need a second medicine?'  Symptoms of uncomplicated chickenpox are normally controllable with one antipyretic.  If the child is unwell despite this, consider the possibility of a secondary infection.


3. Chickenpox causes a rash for a week and a fever for a few days and then it gets better

Except when it doesn't...

While the vast majority get better without complications, chickenpox causes a suprising number of children to get a rather unusual neurological condition: cerebellitis (also called post viral ataxia).  This is a post-infective phenomenon which tends to present in the weeks immediately after the infection, often as the lesions are well crusted or even fading.  Typically the child presents with ataxia.  Other symptoms include clumsiness and difficulty maintaining posture.  Nystagmus and other cerebellar signs may be obvious.  There is no treatment needed but children should be assessed by a specialist to confirm the diagnosis.  Imaging is not needed as long as there are no atypical features and the symptoms begin to improve after a couple of weeks. (4)


So, the internet ruins any attempt to hold onto our faith in simple facts.  This is partly because facts are rarely simple and often wrong.  All of the three bold statements above were things that I was told and believed at some point in my career.  Finding out the truth takes a little looking and a lot of thinking but you get to find out some worthwhile things along the way.  Or, you could just let an expert tell you the facts...

Edward Snelson
So very not an expert
@sailordoctor

References
  1. Atkinson, William (2011). Epidemiology and Prevention of Vaccine-Preventable Diseases (12 ed.). Public Health Foundation. pp. 301–323. ISBN 9780983263135
  2. Heininger, U., Varicella, The Lancet, Vol 368, Iss 9544, 14–20 Oct 2006, p1365–1376
  3. Zerr DM. et al., A case-control study of necrotizing fasciitis during primary varicella, Pediatrics. 1999 Apr;103(4 Pt 1):783-90.
  4. Nussinovitch M. et al., Post-infectious acute cerebellar ataxia in children, Clin Pediatr (Phila). 2003 Sep;42(7):581-4.


Sunday, 4 September 2016

Gastroenteritis in Children - Ten Myths


Vomiting and diarrhoea in children is usually caused by viral gastroenteritis.  There are lots of myths surrounding gastroenteritis and how best to manage it.  I find myself repeating things that I was once told years ago and have to check from time to time whether the 'fact' is in fact based in any reality.  When I find out that it was all a myth, it makes me feel so much better when I later hear other people who hold those same myths to be true.  Hopefully, between us we can dispel a few of them.  Here are a few non-truths that I regularly come across:

1.  It's just a virus.  I know that I said it is usually a viral infection in children and that is true.  However that should not fool people into thinking that it is a benign illness.  Even in well nourished children, dehydration is a real risk and every year previously healthy children with gastroenteritis suffer renal failure and other consequences of severe dehydration.  Avoiding dehydration makes for most of the dos and don'ts of gastroenteritis.

2.  Paracetamol should be avoided because it makes the child vomit.  Not so.  What is more nauseating: 5 mls of liquid vitamin P or fever and abdominal pain?  Giving paracetamol is likely to help resolve the vomiting and make the child feel more like they could cope with drinking a few sips of water.  Certainly, children often do vomit shortly after being give paracetamol but when it works, it is well worth it.

3. You shouldn't give milk to children who are vomiting.  The best fluid depends on two factors.  One factor is the level of hydration.  If a child is at risk of or is becoming dehydrated then oral rehydration fluid (ORF) is recommended.  The second factor is the question of what the child will take.  Oral rehydration is really important, so better a bottle of milk that is drunk than a bottle of ORF that is continually refused.  The important thing to avoid is the list of drinks that will make matters worse.  Milk is not on that list.  Just because milky vomit is nasty compared to when the child is drinking clear fluids doesn't mean you should avoid milk if that is what they will take.  Milk contains carbs and electrolytes and for babies it is the fluid of choice.

4.  Flat cola is great for rehydration.  What makes a poor rehyration fluid?  Acidity to worsen gastritis as well as hyperosmolality and added chemicals that will drive diarrhoea.  Flat cola ticks all of these boxes which is why it gets a special mention in the 'don't do it' bit of the NICE guidelines for gastroenteritis in the under five year olds. (1)


5.  You can't give antiemetics to children.  Now we are getting into more controversial territory.  Antiemetics such as prochorperazine and metoclopramide (where would I have been as a house officer without these two drugs?) are traditionally avoided in ill children due to the risk of dystonic reactions.  It has threfore been the case that gastroenteritis has always been in that category of illnesses that just has to get better on its own.  That may be why the world of paediatrics has failed to reconsider this view despite the appearance of newer and safer antiemetics.  There is good evidence for example that ondansetron reduces vomiting and may aid rehydration (2).  So why don't we use that when a child is failing to rehydrate orally?  NICE considered this when writing its guideline and noted that ondansetron is also associated with increased diarrhoea.  The answer was therefore that it could not yet be recommended, but possibly with more research, ondansetron will be recommended in specific circumstances.

6. You can't give antidiarrhoeals to children.  Again, NICE considered the pros and cons of this option.  There are various types of antidiarrhoeal medicines, each of which was decided against in turn, mostly on the basis that there was no evidence for benefit.  In the case of loperamide, there is reasonable evidence that it does help (3).  So what's the problem?  Loperamide is not licensed for use in children in the UK (and I think the same is true in the USA and Australia but I'm not sure about elsewhere).  However, the BNFc does list doses and acknowledges the license issue.  I don't intend to medicalise self limiting gastroenteritis, but if I thought it would help, it is good to know that it is therapeutic option.

7.  A period of starvation can resolve vomiting or diarrhoea.  The only clinical value to an enforced period of starvation for a child is that it is a great way to diagnose MCADD.  Witholding food or drink will not change the course of viral gastroenteritis.  However, some children do have underlying, yet hidden metabolic disorders of energy production.  These children have often had no manifestaion of their disorder because they have never run out of immediately available energy.  When they are unwell and rely on ketones, everything goes wrong and hypogylcaemia can come on profoundly and unexpectedly early into a period of fasting.  Any ill child who is not getting calories and who becomes subdued or agitated should have a blood glucose checked.


8.  It's a 24 hr bug.  In fact who knows how long it will last.  I don't believe that you can make something go wrong just by saying a thing.  For example, I am very happy to walk around at work commenting on how lovely and quite it is and enjoy seeing the superstitious flinch at this.  However predicting the length of a gastroenteritis is a recipe for perplexed parents.  Vomiting usually settles by day 3 and diarrhoea should be at least much improved by day 7.  Should be...
If diarrhoea is not resolving at day 7 then consider doing a stool sample.

9.  It's probably food poisoning.  Thankfully not.  The vast majority of vomiting and diarrhoea in children is viral gastroenteritis.  Bacterial infections are more likely if the child has been to an area with endemic infection.  A history of consuming foods that are likely to have been contaminated is also important.  A sudden onset of vomiting does not imply food poisoning though.  Norovirus for example typically causes sudden and severe symptoms.

10.  Dehydration requires intravenous fluids.  Rehydration is best provided through the gut, not a vein.  Although guidelines are changing in order to avoid dangerously hypotonic fluids, intravenous rehydration will always be risky.  Every effort should be made to achieve oral hydration.  If this fails then nasogastric rehydration has a good evidence base.


Of course these are only the myths that I used to believe before my faith was destroyed by reasoning and evidence.  Do you have any of your own?  If you know of a wrong but popularly held belief to do with gastroenteritis then please post it in the comments below.  Cheers!

Edward Snelson
Grade 'O' in Care of Magical Creatures at O.W.L.
@sailordoctor

Disclaimer: It feels a bit strange to be in agreement with so much of a NICE guideline.  I may be coming down with something.

References
  1. Diarrhoea and vomiting caused by gastroenteritis in under 5s: diagnosis and management NICE guidelines [CG84]
  2. Szajewska H et al., Meta-analysis: ondansetron for vomiting in acute gastroenteritis in children, Aliment Pharmacol Ther. 2007 Feb 15;25(4):393-400.
  3. ST Li et al., Loperamide therapy for acute diarrhea in children: systematic review and meta-analysis, Database of Abstracts of Reviews of Effects (DARE)