Chest Trauma in Children

"Know the likely injuries through different age groups including pulmonary contusion and flail chest"

Isolated significant chest trauma is rare in paediatrics, but is still the second highest cause of trauma related death in paediatrics (although whether the death was caused by the chest or by other injuries is difficult to tell). There is an excellent handbook from the Royal Children's Hospital in Melbourne which probably  tells you everything you need to know. There is a 2008 review in "Trauma" and a really nice overview presentation here.

Most chest injuries are caused by blunt trauma and  RTCs, and are normally associated with injuries elsewhere. The anatomy is similar to adults (excellent podcast here), but children are different - especially if they are younger:

• Smaller
• Traumatic forces distributed over a smaller mass
• Smaller thoracic volume
• Compact organs

• Increased chest wall compliance
• Ribs unlikely to break
• Internal injuries likely with minimal external signs
• Compensatory mechanisms may mask hypovolaemia
• Mobile mediastinum
• Airway injuries rare
• Mediastinal shift may cause problems
• Aerophagia is a common response in children
• Causes reflex ileus
• Leads to gastric dilation 

As in adults, there are six life threatening chest injuries to remember, remembered by the mnemonic "ATOM FC". These should be identified on the primary survey:

"ATOM FC"

 - Airway Obstruction

 - Tension Pneumothorax

 - Open pneumothorax

 - Massive haemothorax

 - Flail chest

 - Cardiac Tamponade

The Trauma journal review also reports there are six "hidden" but life threatening injuries:

-Cardiac contusions

-Aortic disruption

-Tracheobronchial disruption

-Oesophageal disruption

-Diaphragmatic tear

-Pulmonary contusion

We're hopefully pretty good at identifying the life threatening injuries. Often we suspect the "hidden" injuries. But how do we make the final diagnosis, especially as we know that we don't want to do unnecessary CTs on children.

This short presentation introduces some clinical decision rules to help you decide who needs chest imaging. Using a paper from the Annals of Emergency Medicine (which I can't access as it doesn't support Athens or Institutional Access) they suggest we only do a CXR in trauma if:

• Low BP/Increased RR
• Abnormal chest exam
• GCS<15
• Femur fracture

After trauma, most children I've seen have got an increased respiratory rate, so making sure we do a CXR for everyone doesn't seem unreasonable.  What about CT?

Pediatric Radiography have looked at how CT changes our management of paediatric patients. Again, I can only access the abstract:
235 children had a CXR and a CT done. In 1/3 CXR abnormal, and in 2/3 CT was abnormal.
Out of all the children, <5% got any chest procedure

<10% of kids with pneumothorax on CT got a chest tube
91% of CT findings were within 1cm of dome of liver --> visible on CT abdomen.

So this study would suggest that routinely doing a CT chest on all children may be unnecessary. Given that most of our treatment for chest injury is analgesia, and supporting ventilation, CT rarely changes management. Not all pneumothoraces are treated with a chest drain.
I'm not sure I'd be ready to chance hospital policy yet, but it is certainly something to think about! 

Lung Contusion
This is the most common chest injury in children, and can occur without chest wall injury.

Diagnosis:
-  Hypoxia
-  Consolidation on CXR (in 90% on initial CXR)
        - May be irregular and not conform to lobes
- CT scans pick up more scans
       - 38% of dogs experiencing blunt trauma had consolidation on CXR, compared to 100% on CTs


Treatment:
- Oxygen
- Analgesia
- Pulmonary toilet
- Ventilatory Support

Flail Chest
Flail chest is very rare, but can happen. The paraxodical chest movement caused by two or more rib fractures contributes towards respiratory distress. These often occur with pulmonary contusions. There is a very good explanation with some excellent pictures here.

Treatment
- Place the patient injury side downwards
- Intensive respiratory support
- Analgesia

Radiography Risk

There's lots of data about the dangers of CT scans, and we certainly do a lot of scans in the Emergency Department. Although not specifically mentioned in the CEM syllabus, I think it is an unspoken part of every test we request, especially head CTs. I don't think we quite "order numerous CT scans each shift, and dole out radiation exposure dwarfing the atomic bomb dropped on Hiroshima" but we are getting closer than we used to! Just as the sports medics are reducing the number of scans they do, so do we need to.

If you're like me and don't know a lot about radiation, PEMMorsels has a good introduction, as does the Short Coat:

• 1 Sv= 100 rem.  We use milliSieverts in most medical imaging.
• Neoplasms have typically been associated with radiation in excess of 50 mSv
• Background radiation = 3.5 mSv/year 
• Background Cancer Incidence = 420:1000 (42%)
• Medical radiation is between 0-100 mSv

 Although x-rays have a radiation risk, we worry more about the risk of CTs - as summarised on LITFL:

• Routine abdominal CT scan estimated exposure quoted as 8-10 mSv
• Actual calculated radiation: Average 11-20 mSv (Range 4-45 mSv)
• Multiphase abdomen and pelvis CT scanning: median 31 mSv (Range 6-90 mSv)
• Chest CT for suspected pulmonary embolus: median 10 mSv (Range 2-30 mSv)
• Routine head CT median:  2-3 mSv (Range 0.3-6 mSv)

With these radiation doses, we might easily be causing pathology:

• 2-3 brain CT triples the risk of brain tumours
• 5-10 brain CTs triples the risk of leukaemia
• Per 10,000 patients, a head CT might cause a brain tumour and leukaemia in one person. 
• At 10 mSv Lifetime Attributable Risk of developing a cancer is 1:1000 
• One additional cancer for every 4000 CT heads.  

So, as Clinicians we need to be able to balance the risk of a CT vs the risk of undiagnosed disease. Especially in children, the views of the parents often play a part in our decision making process, and maybe we should be gaining consent. If you'd like to be able to instantly show your patients their risk of cancer from a CT, there is a clear graphical display here, and there is a nice PV card here which unfortunately doesn't cover the paediatric population. X-ray risk has a more precise risk calculator, but again only estimates the risk in children.

And this is the risk if it all goes right! If it goes wrong, the doses could be a lot more.  And if there is a radiation emergency, what would you do?

Times are changing, and we're moving away from CT scans, and towards observation.  So think carefully before you do the CT scan.

All of this is nicely summarised by St Emelyns - there is often no right answer, and you have to balance the risks.