​

Hey Reader,

Welcome to another edition of Bursting The Bubbles, DTFB's newsletter with some top tips, evidence highlights, and the best dad jokes.

This week we look at ET tube insertion, VP shunts, and how to read a scientific paper.

Let's do it...

​

WEEKLY BUBBLE WRAP: DO YOU HAVE THE RIGHT ENDOTRACHEAL TUBE?

​

What’s It About?

Precise placement of endotracheal tubes (ETT) can reduce the complications associated with intubation e.g. pneumothorax and atelectasis.

Though the gold standard for evaluating the placement of ETTs is a chest X-ray (CXR), we often rely on formulas (of which there are many) to estimate the correct depth.

This study compared age, weight, and height-based recommendations for ETT depth for children over the age of 28 days (as their guidelines stipulate that those under this age have to be intubated using a nasotracheal route).

​

​

Two evaluators used CXRs to retrospectively evaluate the distance between the ETT tip and the carina and looked at demographics such as sex, age, weight, height, and intubation route. The optimum ETT to carina distance was compared to age-appropriate standards. They excluded patients with airway anomalies and those with tracheostomies.

Using the information from 167 intubated patients (ages ranging from 0 – 17.9 years) in an intensive care setting in Germany, they used four-parameter logistic regression analysis to develop the best-fit curve to plot the ETT to carina distance compared to demographics such as age, weight or height.

Overall, height-based formulas resulted in more accurate ETT placement. However, these formulas are not linear and are only reliable during a limited period in the child’s growth. Using these formulas universally can lead to significant malposition rates. As such, they developed their own table of suggested ETT depths based on height, recognising that their recommendations require future validation. They do not replace CXRs as the gold standard.

The height of the patients was measured in the PICU using a Broselow tape. This is not always feasible in an acute resuscitation scenario.

For a deeper look into intubation in the critically unwell child, check out Vicki Currie’s article on Intubation of the critically unwell child in the emergency department.

​

Why does it matter?

​Both APLS and EPALS use weight as the basis of the ETT depth formula, but this study demonstrates how these formulas are not always reliable. We can often eyeball a patient and judge whether their weight correlates to the WETFLAG formulas; though we could use a more accurate and reliable table to estimate ETT. This would be preferable if we are waiting for CXRs to confirm the position.

​

Clinically relevant bottom line:

Using age as the basis for EPALS/APLS formulas for ETT insertion depth is unreliable. It assumes a linear relationship with weight and height. This group has developed a height-based guide for ETT insertion but recognise that measuring the height of a patient may not be feasible within an ED setting.

​

Reviewed by: Lucine Nahabedian. Read the full Bubble Wrap here.

​

Get Your DFTB Essentials Ticket! Tickets for our online course are on sale now. ​ Live on 28th November with lifetime access. ! I want my DFTB Essentials ticket!

TOPIC OF THE WEEK: VP SHUNTS

​

What is a VP shunt?

A ventriculoperitoneal (VP) shunt is a medical device used to drain fluid via a pressure gradient away from the brain for excessive cerebrospinal fluid (CSF) conditions. The intention is to shunt fluid away and avoid undue pressure on the brain. It is one of the commonest performed neurosurgical procedures and is the treatment of choice for most patients with hydrocephalus.

Shunts drain according to the differential pressure gradient between the ventricle and the tip of the distal catheter. The ventricular end of the catheter is inserted through a burr hole in the right parieto-occipital region, and the valve often sits behind the right ear. The distal portion is subcutaneously tunnelled into the abdomen, positioned inside the peritoneal cavity.

The diagnosis of raised intracranial pressure in children with VP shunts is challenging. The symptoms are non-specific, and the commonest causes are often benign. Rhiannon could easily have a simple viral illness, or her symptoms could be associated with rising intracranial pressure. Missing a shunt malfunction in these patients can be catastrophic.

Shunting CSF is an effective way to avoid the neurological damage that ensues if the build-up of CSF is left untreated.

Three shunt types are mainly used to shunt CSF: Ventriculoperitoneal (VP), ventriculopleural (VPL), and ventriculoatrial (VA). By far, the commonest are VP shunts.

​

Shunt related complications

Failure rates are quoted as 30-40% at 1 year and 50% at 2 years in the paediatric cohort. A patient can expect to have 2-3 shunt revisions over the course of 20 years and the median time to shunt failure is just 1 and a half years. Paediatric revisions are more commonplace than adult revisions.

Risk factors for shunt failure include:

• Younger patients (<6months), particularly neonates
• Complex comorbidities, for example, cardiac, myelomeningocele, IVH’s, tumour and post-meningitic hydrocephalus, spinal dysraphism, and congenital hydrocephalus
• Prior shunt failure and short time intervals between revisions
• Male sex
• Low socioeconomic status

​

Causes of VP shunt failure include:

• Obstruction, blockage, or occlusion
• Shunt infection
• Shunt fracture
• Shunt disconnections
• Abdominal pseudocyst
• Shunt migration
• Overdrainage

​

Clinical presentation of VP shunt malfunction

Children with a blocked shunt can present with a myriad of symptoms including:

• ​headache​
• nausea
• vomiting
• fever
• irritability
• abnormal level of consciousness

Infants and older children may present differently.

Infants

• difficulty feeding
• bulging fontanelle

Older children may present more specifically with

• Nausea, somnolence, lethargy, cognitive difficulties, or eye pain.

Predictably, fever is commoner in children with shunt infections. Those with shunts because of myelomeningoceles may present with symptoms such as:-

• weakness,
• difficulty walking
• bowel/bladder dysfunction
• lower cranial nerve palsies

Children present with these symptoms all the time to the ED. They are clearly not specific to a shunt problem. As a consequence, diagnosing shunt malfunction on clinical grounds alone is incredibly difficult. Patients with shunt fracture or disconnection can present with a slow onset of symptoms. They may have pain/tenderness localized to the area of fracture/disconnection or an area of calcification of an area of fluctuant swelling.

​

Diagnosis, evaluation, and imaging

The diagnosis of a shunt malfunction requires a combination of CT, shunt series radiographs, and occasionally (though seldom in the ED), CSF sampling.

A CT is likely to show an increase in ventricular size and occasionally, periventricular lucency representing oedema. There may be increasing ventricular size on cross-sectional imaging but up to 15% will have “such profound alterations on brain compliance that their ventricles will not enlarge in the face of shunt failure and increased ICP”. Ventricular size doesn’t appear to reach a plateau until approximately 14 months after placement of the shunt (regardless of type implanted).

A lumbar puncture (LP) may demonstrate increased opening pressures, but not always. It is also used for evidence of infection. This is not performed commonly in the ED in the context of possible shunt malfunction.

Shunt series radiographs are used to check the overall course of the catheter, looking for disconnection or disruption. The series will not show obstructions, only damage to the catheter. It can rarely demonstrate complications such as a CSF pseudocyst (abnormal separation of bowel loops near the catheter tip) but shouldn’t be relied upon for this.

The number of radiographs needed varies according to the size of the child. It is usually 3-4 radiographs, including two views of the skull and the continuous trajectory of the shunt tubing down the neck, chest, and then looping into the abdomen.

If a series is performed after the scan, theoretically a 2 view skull radiographs can be eliminated, provided that the chest x-ray includes the base of the neck. Unnecessary radiation may then be avoided.

The use of ultrasound is an area of ongoing research and has been largely unvalidated in children with VP shunts.

​

Read more about VP shunts in Angharad Griffiths' article here.

HIGHLIGHT: HOW TO READ A SCIENTIFIC PAPER

No matter where we are or what type of medicine we practice, it is likely that we all were told at one point that we were expected to be lifelong learners.

This is important as medical knowledge is constantly evolving. Dr. David Sackett, the father of evidence-based medicine, once said:

The traditional way to stay current is by reading the relevant scientific literature. Except there’s one problem…

Nobody ever actually teaches us how to read a research paper…

​

Anatomy of a paper

Let’s start with the basics and talk about the sections of a paper.

Most traditional research papers have these key sections.

1. Abstract – A summary of the entire paper
2. Introduction – Provides some background on the topic and sets the stage for the research question being addressed in the paper.
3. Methods – How the researchers went about answering the research question and what analyses were performed
4. Results – What the researchers found out
5. Discussion – A bit more in-depth talk about the results and limitations of the study
6. Conclusion – What the authors think you should take away from the study

​

Bias

Whenever we pose a question in science, we embark on a noble quest for truth (or at least a point estimate of truth with a surrounding 95% confidence interval). The problem is that most research studies are imperfect and have biases. Biases are things that may steer us away from the “truth” we are seeking.

​

It is important to recognize where biases might occur in research and consider how they may impact the study. There’s a whole catalog of potential biases!

​

But let’s start from the top:

​

Abstract

Read this to determine whether or not this paper is of any interest to you or helps you answer a clinical question. If the answer is no, move on and don’t read this paper.

​

Introduction

Unless you do not have any experience or knowledge of the topic being addressed, you can safely skip this section. Authors craft a compelling narrative for why their research topic is important, but this section is subjective. It is not a comprehensive summary of all the previously existing literature on the topic.

​

Methods

This is one of the most important sections of the manuscript. Think critically about whether or not the research design used by the authors to answer their research question was appropriate. Pay attention to what primary and secondary outcomes were specified. Are they patient-oriented outcomes?

​

If the methods are inappropriate for answering the research question, stop reading. The results and remainder of the paper are likely not useful or reliable.

​

Results

If the methodology is appropriate, then read the results.

See if the authors reported the primary and secondary outcomes specified in the methods section. Sometimes, there may be discordance here.

Do not just read the text of the results. Scrutinize the tables and charts. The authors sometimes won’t mention everything in what they write. Also, do not forget to review the supplemental material or appendices. You can often find some great information there in the details.

After reading and thinking critically about the methods and results, STOP.

Draw your own conclusions.

Wait what? What about the rest of the paper?

​

Discussion and conclusion

You can choose whether or not to read these two sections after you have stopped and drawn your conclusions based on the methods and results.

These sections are also subjective because they represent the authors’ opinions. The authors may provide insight in their discussion about challenges or limitations… or not. After all, who would want to reveal all of the reasons why you should question the conclusions of their research?

​

Determining the quality of a study

Checklists or guides can be handy to help you determine the quality of the study.

Some examples include:

• ​JAMA Users’ Guide to Medical Literature
• ​Best Evidence in Emergency Medicine Critical Appraisal Tools
• ​CASP Critical Appraisal Checklists

You do not have to use all of these tools, but choose one and be consistent!

​

To read more about this see Dennis Ren's full post here.

EVENT OF THE WEEK

Next week is World Diabetes Day.

It can be hard to keep up with current management, so DFTB does it for you.

Check out Dani Hall's post on DKA management here.

​

TIP OF THE WEEK

If you're having a rough day, remember that kids have an uncanny ability to say the most unexpected and hilarious things, guaranteed to make you smile.

​

JOKE OF THE WEEK

How does a penguin build its house?

​

Igloos it together!

​

That's it for this week, Reader.

​

Remember, your work makes a difference in the lives of paediatric patients every day.

​

Stay tuned for next week's edition of Bursting The Bubble.

​

From Tessa (on behalf of Team DFTB)

​

P.S. If you want to forward this email to someone who would enjoy the newsletter too, they can sign up here.

​

No longer interested in these emails? Click here to unsubscribe​