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

  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.

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

  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)