Tasty Morsels of EM 138 – Ultrasound in kids

29 Jan

This batch of the tasty morsels series are various pearls and learning points from my most recent 6 months doing paeds EM. I’d done a fair bit of paeds before but never in a dedicated children’s hospital and it was all a long time ago. Turns out there’s always more to learn. These are mainly observations and anecdotes even more so than usual!

Ultrasound for LP

The commonest reason we do LPs in kids is the febrile neonate. This is currently shifting ground and consensus is somewhat lacking but the certainly under 2 months a child with a fever will end up getting an LP whether or not you find a UTI or a bronchiolitis or whatever.

So for now there’ll still be lots of LPs in tiny babies. In general I find them easier than adults. The distance involved from skin to CSF is much shorter and generally the landmarks are fairly easy to identify.


  • Sit the child up
    • there are few things that look more awkward than a sitting neonate. They’re just not really built for it. So you need a skilled holder (probably more important than the person with the needle!!!)
    • I only did this for the first time in the past 6 months and found it a massive improvement. Makes finding the mid line and keeping the needle perpendicular to the spinal canal much easier
    • There is an RCT on this that showed no significant difference in lying versus sitting so this one definitely seems to be a personal preference on my part
  • Ultrasound
    • I’ve done this in adults quite a bit and find it useful. Like with a lot of ultrasound things you do need a degree of competence and confidence in interpreting the images otherwise you can just confuse yourself. And it’s still and adjunct, not a magic bullet
    • In kids the anatomy looks beautiful and it allows you to mark the ideal site and have an idea of depth from skin to CSF pocket. That way you don’t put the needle in too far and end up with urine from an LP which is never a good look…
    • The most recent paper I’ve seen on this is this one which we also discussed on the RCEM Learning podcast
      • they had 130 patients randomised to ultrasound guided LP or not
      • ultrasound increased first pass success from 30 (pretty awful) to 60% (acceptable)
      • They were mostly very novice proceduralists

Ultrasound for IV access

This is pretty much my all time favourite ultrasound application and was keen to see how it fitted in with kids. I spent the first month trying to optimise it for the really tiny bubs and it was less than satisfying. Definitely had a few successes but 24G or 26G cannulas are almost impossible to visualise with a standard linear probe and the wriggliness at the ACF just makes it tricky.

My favourite tip was to use it in a similar manner to the ultrasound for LP. Instead of live guidance I’d use an “X marks the spot” on the back of the hand as a guide for where the vein was. This works best in the 6 month old “michelin” baby with rolls of fat. You know there’s probably a vein over the ring finger metacarpal but you just can’t see it. The Ultrasound lets you see it and mark it and then you just proceed with your normal cannulation technique.

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