The TPR paradox - how do I know if a child might have sepsis?

When I assess an ill child, I am primarily making a decision about whether the child has possible sepsis.  To a certain extent, everything else is detail.  The sepsis question determines which door the child leaves through.  Just like in primary care, I send the vast majority of children presenting to the ED back out the way they came, whether they have pneumonia, urinary tract infection or just a cold.  A small number of ill children are admitted, with the possibility of sepsis as the primary reason.  The question is: How do I decide which door to send each child through?  Once you answer that, I believe that you can begin to understand how to use the many guidelines and decision tools designed to help us make this choice.

In 1935, Einstein and two of his buddies published a paper detailing some problems with quantum physics theories.  In effect they were saying that their own advances had explained a lot about how physics worked, but that there were some things that they could not explain.  Specifically, when two particles went through two doors, one of them did something that didn't make sense.  You could do something to one of the particles and the other reacted even though they are not connected.  This is called the EPR paradox, after Einstein, Podolsky and Rosen.  These three were the best scientific minds in the world and yet they had a missing piece of the jigsaw so big that it called everything else into question.

I believe that we are in a similar place in medicine when it comes to recognising possible sepsis in children.  Once again we have two doors and sending children through these is not as straightforward as it should be.  We all do our best to send each child through the correct door.  There is a big piece of the jigsaw missing though and that’s got us all scratching our heads.  The missing bit is knowing how to go from considering possible sepsis to diagnosing probable sepsis without resorting to reading tea leafs or other substitutes for a valid test.  Most of the time we do our best and accept that in the absence of a good test all we have is good judgement.  The problem comes when a child dies of sepsis and that gap in the process comes under scrutiny.  I'm all for completing the puzzle but I am suspicious that we are trying to put the wrong piece into the gap.

If I asked you to create a decision tool for clinicians to move from considering sepsis to a provisional diagnosis of sepsis, what would you choose as predictors?  You could use the appearance of the child but that is difficult to quantify.  What seems far more reliable is TPR (temperature, pulse and respiration) since these can be measured.  The trouble is that the most measurable features of your assessment are the least reliable.

Before I get a rush of people saying that I think that you should ignore tachycardia and high temperature, please be clear that I don’t think that.  It is just that I think that there is a much better category of evidence and that numbers are not as reliable as we want them to be.

There are plenty of reasons to mistrust numbers.  For starters we have a lack of reliable reference ranges.  There is a good reason why no-one has started making a lot of money out of selling centile charts of paediatric heart and respiratory rates.  They don't exist.  There is not enough evidence to produce such a thing.  The variables are just too many.  Is it age that determines heart rate or your weight?  If it is weight then is it lean weight?  What is the effect of anxiety on heart rate?  How different is a normal heart rate in a resting child to that of a playing child or a screaming child?

What about those normal ranges that you have somewhere when you need to check?  Aren't they evidence based?  You could try to find out what their evidence base is but I could probably save you a lot of hassle by telling you that all the normal ranges that I know of are based on consensus, which is why they are all slightly different from each other. In the past few years, two large analyses have shown that some of the most commonly available reference ranges map poorly to population studies.  Even then, these publications acknowledge that the populations studied are never truly normal. (1,2)

However, I think that this whole issue is much simpler than all of that, because the wrong question is being asked.  The question is not, “Does this child have sepsis?”  The question is, “Can I say with confidence that this child does not have sepsis?”  When we use the rule out rather than rule in approach, everything starts to fall into place, including the value of numbers.

I said before that there is more reliable evidence than temperature and pulse.  That evidence is something that you rely on every time you assess a child and it is the thing that makes sense of the numbers for you: activity.   What we really want to know about the heart rate and capillary refill is not the absolute number but the effect that these are having.  What we need to assess is oxygen and glucose delivery to the organs and there is no better measure of this in a child than what the child can do once these get there.

There is one more variable which complicates the TPR paradox, which is the up and down nature of the illness.  You may see the child at their worst or possibly their best.  In any viral illness the likelihood is that the child will have extremes of activity making nonsense of the assessment.  Thankfully we have two saving graces here.  The first is that we can hear about what has gone before.  The second is that we are able to continue the assessment either by observing, referring or safety netting.

So let’s bring all of this together.  There are two simple elements to recognising serious infection in children.  The first is a hierarchy of evidence.  The second is a rule-in/ rule-out approach.

The hierarchy of evidence is logical.  If I see a child in a playground climbing up to go on the slide and their parent mentions that they have had a temperature, I don’t worry that they may be septic.  I do imagine that they have a significant tachycardia but this will be a result of their activity and possibly their temperature.  I see with my eyes both the activity and the vigour with which it is undertaken.  I don't need to ask any questions or measure any physiological parameters because I have all the evidence that I need.

If I was giving telephone advice and I hear that a child is sat playing on a tablet I now have some very useful information about the adequacy of their brain’s perfusion and oxygen/glucose supply.  It's not as good as what I see because I can't scrutinise what I am being told with my own experienced eye.

Finally if I measure a child’s heart rate and capillary refill, I have information but it needs to be put into context.  Was it cold outside?  Have they just been upset by something?  So the numbers are important but I need what I see and hear to make sense of them.

In any acute assessment of an unwell child this hierarchy can be combined with a rule-in/ rule-out approach to answer the question, “Am I certain that this child does not have sepsis?”

If what you see, hear and measure is all reassuring then the answer is yes, they do not have sepsis.  If what you see, hear and measure are all concerning then the answer should be no, they could well have sepsis.  If what you see, hear and measure give a mixed message then the question remains open and there are various ways to answer it.  Using the hierarchy of evidence above, I feel confident to give paracetamol and wait when a child looks well and behaves well even if they are febrile and tachycardic.  The options are always the same: discharge with safety netting advice, observe, discuss or refer.

Just like the scientists of 1935, none of us has all the answers.  None of the decision tools available is even close to perfect and all of them rely on someone at some point taking responsibility for making a decision about which door the child will go through.  Thankfully the majority of children answer the question for you.

Edward Snelson

@sailordoctor

If you liked this you might also like:

In Praise of Doing Nothing (Easter Egg – good safety-netting and saving lives)

Or How special is your patient? - (Neonates and other patients who don't follow the rules)

References:

(1) Fleming S et al, (2011). Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies. The Lancet, Vol 377, no 9770, 1011-1018.

(2) O'Leary F et al (2015) 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, Arch Dis Child, 100, 733-737

  

Is this really an injury or something else?

This is a magical time of year for the British paediatric emergency physician as children and young people are getting far fewer illnesses.  Instead of wall to wall snot and vomit, the paediatric waiting area is filled with injuries of all varieties.  Although I assume that obvious fractures will present directly to the Emergency Department, many injured children will also present to primary care.  This tip applies equally to both settings.  Hidden amongst all of the injured children will be a ‘something else’ from time to time.  They are particularly hard to spot but there are a few things that can help.

In most cases there is no doubt that an injury actually is the case of the pain.  If the mechanism fits, go with it.  (Well doc, he cycled off the roof.  Do you think that’s why his leg hurts?) What we are talking about here are soft presentations.  These are  the things that present as injury but are in fact the manifestation of something else:

• A hip thing (Transient synovitis, Perthe’s or Slipped Upper Femoral Epiphysis)
• Juvenile Idiopathic Arthritis (JIA)
• Infection (septic arthritis and osteomyelitis)
• Apophysitis (the most common being Osgood-Schlatter’s)
• Malignancy (e.g. Osteosarcoma)

Even excluding the odd one out in that list (transient synovitis, or irritable hip to give it its other name), these conditions comprise a surprisingly large number of injury presentations.  So in order to avoid the pitfall of allowing the presentation to frame your diagnosis, ask the following questions:

Is it the hip?

This is a deceptive question but an important one as hip problems are rarely true injuries.  Very often the child either has referred pain to the knee or, if younger, does not localise the pain at all, choosing to blame their foot or another random body part.  So for any lower limb problem without a blatant cause the hip must be assessed.  If the hip is then found to be suspect, what you do next depends on your experience and where you work.  I would suggest that any of these factors mandates urgent referral of a suspected hip problem:

• Age over six
• Fever
• Unable to weight bear on that limb

How long has the pain really been there?

In any of the chronic causes of pain the symptoms may have been present for a considerable time.  Despite this the pain is often put in the context of a football game or other event.  In many cases there was no injury as such, simply a worsening of pain after a fall or an exertion.  Any pain that was there already and was made worse by anything should be assumed to have a chronic cause.  This may be something relatively benign such as Osgood Schlatter’s disease but it may also be something more in need of early detection such as Juvenile Idiopathic Arthritis or a malignancy such as osteosarcoma or leukaemia.

Is the child unwell and is the ‘injury’ hot to touch?

Septic arthritis and osteomyelitis are thankfully both rare in children.  They are also completely devastating and rather difficult to detect.  If infection is suspected, refer and do not allow the buck to be passed back in the form of advice to do some blood tests to rule out infection.  If the onset is acute or the child is very young, inflammatory markers may not yet be raised. (1)  Juvenile idiopathic arthritis can also cause hot, swollen joints and may even cause systemic symptoms.

Is the problem bilateral?

If there are two of the same body part affected (and no good mechanism to explain this) the possibilities are limited.  Thankfully you can essentially rule out infection and tumour.  What becomes much more likely is one of the other possibilities.  Although an apophysitis is more probable if the tibial tuberosity or the Achilles tendon insertion is involved, other bilateral pains make juvenile idiopathic arthritis much more likely.

Have there been other mysterious joint aches over the past months or years?

One of the laments of the paediatric rheumatologists is that children present late with juvenile idiopathic arthritis (JIA).  Recurrent pains in children are often put down to growing pains.  While it is true that young people often get unexplained pains that are not related to any of the above conditions, it is also important to look for the signs and symptoms of JIA.  One of the most important considerations is the recurrent nature of the pain.  Severity is often difficult to assess as children and young people are surprisingly likely to under-report chronic pain.  They tend to assume that it is nothing (after all they haven’t yet learned to worry about all the serious possibilities that occur to their adult counterparts) or simply alter their activity so that the pain has little impact. 

If JIA is suspected, examine the affected joint(s) for swelling and perform a PGALS screen which will detect other joints that are affected which may not have been volunteered in the history.

In summary, most children that present with minor injuries do indeed have minor injuries, with the exception of hip pain, which is usually something unrelated to an injury.  Hip pain aside, it is easy to miss the rare causes of bone and joint pain.  Asking about the mechanism of ‘injury’ and pre-existing or recurrent symptoms may help to uncover chronic causes.  Examination of the affected part and consideration of the possibility of infection are also important if there is any possibility that the history of injury is a distraction.  Any unremitting well localised pain should raise the possibility of malignancy(2) unless another good explanation can be found.  Finally juvenile idiopathic arthritis is uncommon but needs to be actively sought as it is easy to miss.

Edward Snelson

@sailordoctor

Disclaimer:          I’m talking rubbish:  I’ve just had a peek in the waiting room and it is wall to wall snot and vomit after all…

(1)          BRITISH SOCIETY FOR CHILDREN'S ORTHOPAEDIC SURGERY The management of acute bone and joint infection in childhood - A guide to good practice

(2)          Suspected cancer (part 1—children and young adults): visual overview of updated NICE guidance  BMJ 2015; 350 doi: http://dx.doi.org/10.1136/bmj.h3036
http://www.bmj.com/content/350/bmj.h3036