Head injury – the 4-hour observation clock…

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You have just seen a 3 year old boy who, one hour earlier, was running along the street, fell over and hit his head. There was no loss of consciousness, no vomiting and he’s running around the Emergency Department (ED) completely unaware of ‘social distancing’ practices. On examination he’s got a small forehead abrasion but nothing else concerning. The parent was initially concerned (so came to ED) and now wants to go home.

You think this is sensible and speak to your senior who advises that you observe him for 4 hours post-injury. You think he’s got a ’trivial head injury’ with no risk factors and ask why they need to wait a further 3 hours in ED. ‘That’s what we do’ comes the reply…

Paediatric head injuries, arguably, make up a significant proportion of children attending hospital. It’s been suggested and subsequently shown  that a fair proportion could be sent home by a competent nurse at triage even during a worldwide pandemic…

PREDICT have done some wonderful work recently with their ‘Guideline for Mild to Moderate Head injuries in Children – Algorithm’ (2021) – answering questions I have often wondered myself. However, I personally feel the two most ground-breaking of all these recommendations appear to have been glossed over. This may be because they are soooo obvious, simplistic and pragmatic but that makes me love them even more…

Trivial head injuries

Children with trivial head injuries do not need to attend hospital for assessment; they can be safely managed at home’. 

  • How many children in your own experience fall (boom boom) into this category and attended for review?
  • How much money and time (the families and the health services) could be saved if these children stayed at home?

A lot’ would be the assumption for both of these questions. However, this is currently an evidence void in need of answers.

Extended observation OR discharge

It is made very clear that children who do not fall into one of the assorted risk categories have ‘no need for observation’ aka discharge home.

  • No need to stop, pass go or take up sacred ED seating until 4 hours after their medically innocuous injury (agreed, to a parent an injury may not have been innocuous but by medical head injury rules it is).
  • The child stays for no longer than it took to see and assess them. This may be a hard practice to change in many ED’s.

4 hours

How many paediatric head injuries in your own clinical practice do you or someone else say/write the immortal words “Observe 4 hours from injury’? 

Do all the children observed for 4 hours across the world require this?

How many children, that you have seen in your practice, have deteriorated?

Why does this practice exist and what is the evidence base?

Well, there is a clear consensus on who should be observed for 4 hours from injury. In the UK, the National Institute for Health and Care Excellence (NICE) Head injury: assessment and early management CG176, 2014 – – suggests children with the following require observation for at least 4 hours from the injury:

  • Loss of consciousness lasting more than 5 minutes (witnessed)
  • Abnormal drowsiness
  • Three or more discrete episodes of vomiting
  • Dangerous mechanism of injury (high-speed road traffic accident either as pedestrian, cyclist or vehicle occupant, fall from a height of greater than 3 metres, high-speed injury from a projectile or other object)
  • Amnesia (antegrade or retrograde) lasting more than 5 minutes

The latest PREDICT guideline is slightly more prescriptive (especially around age groups) and suggests those with the following risk factors need observation for up to 4 hrs…

But why 4 hours? Why not 3 hours, as someone previously suggested with wheeze?  Why observe them at all and just CT the lot? Well, at the end of the day this is all about risk stratification. A CT scan is not without risk (that small thing called radiation?) and the actual number of abnormal CT’s (ciTBI/TBI-CT) has been shown to be quite low (2.3%) in a large group (19 920) of children with head injuries.  We want to scan those children deemed ‘high risk’ who are more likely to have an abnormal scan not those deemed medium/low risk who are less likely to have an abnormal scan.

The evidence for 4 hours

What evidence is 4 hrs observation based on? Umm, not a lot. Like many practices in medicine, it’s based on consensus and pragmatism. Many institutions follow a 4 hour target for patients to be admitted or discharged from the emergency department. Children with asthma/wheeze seem to require inhalers every 3-4 hours until discharge too and there are, no doubt, countless other examples within the medical world. Four hours observation post-injury is the consensus view and currently established practice from experts with specialist knowledge in this field. It probably came about when you had to sell your kidney to the Radiologist to get a CT scan and radiation doses delivered per scan were a lot higher than present ‘modern’ machines. It was easier to just observe the child and if they deteriorated you could then more easily argue for a scan. This is my best guess but is probably not far from the mark. Could this time be shortened in these at risk groups? Probably. But trying to research this would, no doubt, be an ethical minefield.

The clock is ticking…

There are a small select group of children with head injuries who require a period of observation post-injury, as suggested by national guidelines, decision rules and clinical gestalt. I would argue many children in ED’s across the world that are observed for ‘4 hours post-injury’ do not fall into any of the categories mentioned above and the root cause for observation being clinician preference based on defensive or outdated practice. This is understandable in those who see children infrequently, but should this be accepted going forward?

In the COVID-era we are living through, I believe there will be an increased focus on reducing unnecessary hospital footfall, ED crowding and time in a potentially risky environment. One potential quality improvement project would be to look at your own institution – how many children stay ‘4 hours post-injury’ and how many really needed to…?

About the authors

  • Patrick is a Paediatric Consultant at Frimley Park Hospital. He also plays tennis, badly.

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3 thoughts on “Head injury – the 4-hour observation clock…”

  1. I’d be interested to know if there is any data on patients with low risk features on any scoring system who eventually needed neurosurgical intervention and the mean time to clinical deterioration or intervention.

  2. Good, thought provoking article. Typo in the “extended observation or discharge” section: presumably “SACRED ED seating…” thank you!