Friday, 30 November 2018

Making a Diagnosis of Lower Respiratory Tract Infection in Children

This is one of the most common and difficult calls in General Practice, Emergency Medicine and acute Paediatrics: when to treat a child as a lower respiratory tract infection.  It's important because we don't want to miss a diagnosis of LRTI/ pneumonia, yet overtreating is bad medicine.  It's difficult because most children with an upper respiratory tract infection will have a cough and fever, and because the parents will be worried about the possibility of LRTI.  To make things worse, any child with uncomplicated URTI could later develop LRTI.  Not often, but often enough that it can influence our decision making.  So how do we get it right?

I think that it is a question of rule in/ rule out.  There are many elements to the assessment but there is one feature that determines whether the default is to assume that there is no LRTI and whether the default is to assume that there is a LRTI.  That feature is respiratory abnormality.
I think that when I was taught as a medical student, the auscultation findings in the chest were over-emphasised.  The reality is that these can be misleading.

First of all, the presence of focal findings in the chest are common even in the absence of LRTI.

  • The infant or child with URTI will often have crepitations that can be hear in one or more places in the chest.  These may be transmitted sounds or due to secretions.  Breath sounds will be normal throughout.  In the absence of abnormal breathing, these crackles are not good evidence for LRTI.  Often, these noises go away or move around if re-examined, especially after a cough.
  • The infant or child with a wheeze may have crepitations and variation in the loudness of breath sounds in different parts of their chest.  Bacterial LRTI does not usually cause wheeze but wheezy problems often lead to focal findings.  The clue that the problem is not a LRTI is that the child is systemically well.  The basic rule is this: if a child with a wheeze does not look ill enough to be admitted to hospital, they do not have a bacterial LRTI.  Bronchiolitis and viral induced wheeze are all the explanation needed for abnormal breathing.  If a child had one of these and a pneumonia, they would really be in difficulty. 
  • The child with viral induced wheeze may have no wheeze to further complicate things.  Consider a trial of beta-agonist inhalers in well child with respiratory distress, especially if there is a past history of wheeze. 
Secondly, the absence of focal findings in the chest is a relatively common scenario in the child with LRTI.
  • Auscultation and percussion in infants and small children is difficult.  Chests are small and there is always the possibility that the area of abnormality will be missed.  The child with cough, fever and abnormal breathing should be presumed to have a LRTI unless proved otherwise.
  • Not all LRTIs even produce focal signs.  Sometimes a segment of a lobe is all that is infected (known radiologically as a round pneumonia) and it is quite common in such cases for the only clues to be the combination of unwellness and respiratory abnormality.

Nor should we rely on chest X-ray (CXR) to make the decision for us.  The sensitivity and specificity of CXR as a way to diagnose pneumonia in children is too poor to justify using radiation when the diagnosis should be made clinically.   The BTS guidelines for community acquired pneumonia in children and the Clinical Practice Guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America both recommend that CXR and blood tests are routinely avoided. (1,2)

There are no absolute rules.  This is paediatrics so there are special circumstances.

  • Small infants and babies should be considered to have a higher probability of serious bacterial infection whenever they present.  However that should not mean a liberal use of oral antibiotics in a community setting.  If you are treating them differently because they have that higher risk of serious infections, they are also high risk for other reasons and should usually be referred if LRTI is suspected.
  • Children with complex medical problems may not demonstrate abnormal breathing or unwellness in the way that normal children do.
  • Children with chronic LRTI may be less unwell and have little in the way of respiratory abnormality.  Parents will often seem less anxious if the problem is developing more gradually.  Daily cough for several weeks should be taken seriously.  It is not unreasonable to try a course of broad spectrum oral antibiotics but be aware that this may not be the end of the problem.  Underlying causes including foreign objects, bronciectasis and simply unresolved LRTI may need to be ruled out in which case referral will be necessary.

Bringing all of these things together shows that there are two key features.  The first of these is abnormal breathing in the context of an unwell child with cough.  The presence of abnormal breathing almost immediately makes it overwhemingly likely that the problem is LRTI, bronchiolitis or viral wheeze.  The second feature is wheeze, which largely rules out LRTI.  It's almost that simple.  Almost...
For more on how to tell the difference between bronchiolitis and viral induced wheeze, read this post: "Why Do Different Children Wheeze Differently? - Simple, but first you have to understand all of paediatrics"

It is important to remember that LRTI is usually preceded by URTI.  Safety-netting advice is key.  Here's an example of the kind of thing that I tell parents: (3)
Ruling in and ruling out is a dynamic process.  Involving the parents is an important part of that.

Edward Snelson
Not a member of the ruling class

Disclaimer: Knowing whether you approach the problem from primarily a rule in or rule out approach is a bit like knowing whether you are coming or going, neither of which I am usually sure of.

  1. Guidelines for the management of community acquired pneumonia in children: update 2011 British Thoracic Society Community Acquired Pneumonia in Children Guideline Group
  2. Bradley J et al, The Management of Community-Acquired Pneumonia in Infants and Children Older Than 3 Months of Age: Clinical Practice Guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America, Clinical Infectious Diseases, Volume 53, Issue 7, 1 October 2011, Pages e25–e76,
  3. The Essential Clinical Handbook of Common Paediatric Cases, Edward Snelson

Monday, 5 November 2018

How do we diagnose sepsis in children? The Sepsis Jigsaw

Sepsis in children is something that we all fear.  It is difficult to define and  difficult to diagnose early.  This millennium has seen a huge rise in the presence of sepsis in education, campaigns and guidelines.  I believe that one of the reasons that we're talking about it so much is that we're still trying to understand what we mean.  Within that, we are trying to find ways to explain some of the things that we know.  That is because a lot of what we know about recognising sepsis is tied up in tacit knowledge.

Tacit knowledge refers to the things that we know but are not easily explained.  For example, it is  difficult to explain all the elements involved in driving a car.  Much of what we do in our lives relies on tacit knowledge.  How do you find things?  How do you figure things out?  These are far easier to do than to explain.

The very nature of the recognition of sepsis makes it something that needs completely taking apart and putting back together.

Sepsis is not easily definable in the first place.  2016 saw the Third International Consensus Definitions for Sepsis and Septic Shock (1).  This came from a process that involved two previous attempts to find consensus definitions, a recognition that none of the previous definitions were perfect, and a third brave attempt to find a definition for something that is somewhat amorphous.

The resulting definition:  "life-threatening organ dysfunction caused by a dysregulated host response to infection" is a good one and I would agree with it.  However, it does little to help us diagnose sepsis in children.  Recognising severe sepsis is not a great challenge.  Recognising early sepsis in children is very difficult because of the way that children respond to illness.
There is a bit of a misunderstanding that could result from many of the recent guidelines and publications about recognising sepsis in children: that fever plus tachycardia equals sepsis.  Since febrile children are routinely tachycardic, this does not make sense.  The misunderstanding comes from a retrospective approach to guideline definitions of sepsis.  If you look at all the children who were diagnosed as septic, what were the common features at presentation?  Abnormal temperature (high or low) and tachycardia come up a lot.

There are two sides to this coin.  Sepsis in children is not simple.  It is difficult to recognise and thwarted by many biases.  Yet it is deadly and anything that we can do to improve our recognition of sepsis is going to save lives. So complexity is no reason for complacency.
Since we don’t have a retrospectoscope when we see our next patient, we need to have a good way of recognising possible sepsis and serious bacterial infection (SBI) amongst the large numbers of children with uncomplicated illnesses.  If fever and tachycardia are not specific, what can we rely on?  Despite hopes to the contrary, routine near patient testing (e.g. CRP) in a primary care or emergency department setting will not give us the answer.

If neither numbers nor tests can sort the few out from the many, what is left?  Simply put, a global assessment made by an experienced clinician is what really brings the magic to the decision making.  So what is it that helps them to make a decision?  The answer is complicated but essentially, they put together a jigsaw of features and come up with enough of a picture so that the puzzle makes sense.  Some of the jigsaw pieces are fairly obvious but some of them are less well known or involve that tacit element of the process.  It is worth being aware of the various factors that influence this crucial decision.

The pieces of a sepsis jigsaw puzzle:

Abnormally low or high, infection will affect temperature in some way.  This is an oversimplification which fails to address some of the subtleties of temperature and its relationship to bacterial infection and sepsis.

Factors to consider are:
  • Low temperature in the context of an unwell child is more indicative of sepsis
  • The relationship between height of temperature and sepsis/SBI is loose.  Although there is a correlation between very high temperatures and SBI, it is a weak one.  Children with viral infections may well get temperatures over 40˚C.
  • Temperatures that are more persistent or fail to come down with antipyretics are often seen as more concerning.  Again, this is a poor discriminator as this can be seen in viral illnesses.  However, it is also true that a child with a persistent temperature may not get the opportunity to demonstrate their wellness by having a little run around.
  • A normal temperature at the time of assessment does not rule out sepsis.
Circulation: Heart rate, central capillary refill and peripheral perfusion
The normality of these factors is quite rightly reassuring.  If outside of a reference range, these features may or may not be significant.  Each of these factors can be affected by pain, fear, pyrexia and environment.  Again, the extremeness of the abnormality is a consideration as is the persistence of deranged markers of circulation.

Respiration: Respiratory rate and work of breathing
Abnormal respiration is more discriminatory for SBI and sepsis, assuming that there is no other reason for being unwell and breathing abnormally (e.g. viral wheeze).  The reason for this is that respiration is less prone to the physiological changes that affect circulation.  Abnormal breathing may be caused by acidosis or hypoxia but is less likely to be due to a simple illness.  This ties in nicely with the definition of sepsis that relates to organ dysfunction.  While circulation changes may be a reaction to an uncomplicated viral illness, respiratory changes are more likely to be due to organ dysfunction.

Significant episodes
Since we might only see the child for a few minutes, it is important to take seriously any significant events that have occurred recently.  Pale, floppy or blue episodes are all notable.  Shivering and shaking are also worth taking into account.  They are not in themselves proof of serious infection.  Any of these things can occur during a temperature spike in an uncomplicated viral illness.  Remember that each of these is only a piece of a jigsaw.  You need to look at the whole picture and if the child is now running around pretending to be Spiderman, they’re probably OK despite the thing that happened.

Fluid balance
A well hydrated child (wet mucosa etc) who is drinking well and has good urine output is what you are looking for here.  Where these things are not adequate, sometimes all that is required is analgesia and a fresh start.  It all depends on how the rest of the pieces of the jigsaw are coming together as to whether it is time to go down a particular path.  Dehydration and poor urine output combined with other features is more significant.

Activity, behaviour and interaction
Now we are truly into the area of tacit knowledge.  (I wondered when he was getting around to that...)   Very little is published about the relationship between a child’s ability to smile, play, run or do anything for that matter and their risk of having SBI or sepsis.  However, it is reasonably intuitive that a child who runs in, smiles and talks the hind leg off of you is less likely to have sepsis than a child who is carried in, interacts little and looks miserable.   These factors rarely feature meaningfully because they are impossible to quantify.  Each appraisal is as different as each child is unique.  I couldn’t tell you what my threshold for ‘active’ or ‘interactive’ is because it will be specific to the child and depends on factors that I could not explain easily.  That is tacit knowledge in a nutshell.  While no-one can tell you what you are looking for in this category, it is an important piece of the jigsaw and should be give the weight it deserves.  Your instinct here is vital.
If you use these things in your decision making then that is completely normal.  An article in Archives of Disease in Childhood this year (2) published a consensus of which behaviours are seen to indicate that a child does not have sepsis.

Parental anxiety
More tacit knowledge here folks.  We will ask about symptoms and are looking to get some fairly specific answers.  Much of what we want to know will feed into the features already mentioned.  However, there may be things going on that a parent will struggle to articulate.  It is our job to distinguish between unwarranted anxiety (“I saw that news story about the child who died of sepsis…”) and the anxiety that comes from  a parent knowing that something is deeply wrong and being unable to articulate the reason why they know that.  The latter is the parent’s own tacit knowledge being given to you in the form of a person who cannot be reassured.

The trajectory of the illness
I believe that this may be one of the most important yet least discussed pieces of the jigsaw.  No one has told me about it and it may be that no one has ever told you, but when I say it, your own tacit knowledge about assessing unwell children will hopefully agree with the following statement:  An illness that has extreme fluctuation in symptoms (i.e. very unwell followed by surprisingly well) is almost certainly an uncomplicated viral illness.  I am talking about the “you wouldn’t believe how unwell they looked” kind of illness.  Sepsis and SBI don’t give you time off.  Viral illnesses, it seems, do.  So much so that a child who was floppy and lethargic can within the hour be smiling, playing drinking and complaining that they don’t want to go home because they want to play with the toys that you have.  It’s not in the guidelines but it is very important because the opposite is also true.  Two children can have the same heart rate, temperature, hydration and appearance, but the one who hasn’t had a return to normal in the past few hours is the one to really worry about in my opinion.
Many of these jigsaw pieces are the more quantifiable and traditional features that guidelines rely heavily on.  The rest are more woolly and difficult to define, let alone describe.  These are the pieces of the jigsaw that only you, the experienced clinician, can piece together.  If you would like to do a bit more reading about decision making in paediatrics, here is an article published in ADC (open access) (3) which further explores that issue.

Interestingly, there is a paediatric decision tool that takes into account some of the tacit knowledge features described here.  The POPS (Paediatric Observation Priority Score) includes features such as gut feel alongside physiological values (4).  This scoring system is both simple and over-simple in equal measure.  While it is quick, easy to do and validated, it only gives you a number at the end, not an answer or a diagnosis.  That number tells you to look at the jigsaw and see what the numbers mean.  The higher the number, the harder and longer you need to look and the better the explanation you need in order to be happy.

The other thing about POPS is that it doesn’t include my much neglected feature: the trajectory of the illness.  I think I’ll make a modified version of POPS which includes this.  I’ll call it POPcycleS.

How do we disgnose sepsis in children?  It remains a clinical diagnosis, best made by someone who has all the pieces of the sepsis jigsaw.

Edward Snelson
Perpetually puzzled physician

Disclaimer - If there is a piece of the jigsaw missing, go back and reassess the child.  They have probably eaten it.