Category Archives: Analgesia

Things We Say We Love But Never Do

We haven’t had that many chances to chat about something that really matters – analgesia. Here’s a post on things to do with needles by Andrew Weatherall. No acupuncture involved. 

I like drugs. I like the ones that make people drift into their own special ether world. I like the ways they bend light right or left. I like the ones that make vessels open, myocytes contract and gates stay open.

I particularly like the ones that find ways to interrupt pain pathways. Whether they antagonise or agonise (not the best derivation of that word, granted) I am a fan of most of them. This is at least in part because so much of the time we could do better with analgesia. For all the techniques at our disposal and all the agents we have, most often the literature I read on the actual delivery of pain relief would be marked with a “Could do better”.

Despite my broad ranging endorsement of pharmacological agents, when it comes to analgesia, I actually think the best option is sometimes the one that lets you use less drugs.

Which is where regional analgesic techniques really stand out from the bunch.

Providing Clarity

I should really specify a bit. Not all regional techniques seem apt for the prehospital or retrieval environment. For starters I really mean peripheral nerve blockade because the neuraxis just isn’t a place for  a needle in the great outdoors.

And not all techniques are quick enough to make the administration feasible, particularly once you consider the positioning and preparation required.

If there is one block that should be right at the top of everyone’s list though it is the fascia iliaca block to make mute a firing femoral nerve.

Of all the blocks I can think of it is the one that should be a ready-grab technique for most prehospital providers. It is quick to perform. It is reliably effective. It takes away big pain. And I’ve heard people mention it as a great technique lots of times in the cosy space of bases in all sorts of spots.

Yet, whichever way I cut my Medline searches, I get < 50 entries in the literature for prehospital care and fascia iliaca block. And when I mention I’ve used it, I sometimes draw quizzical looks. As if I’d suggested a pot of green tea to the kids at a birthday party.

Yet a well performed peripheral nerve block can mean less of all those other drugs we use for analgesia (particularly the opioids or ketamine) and those agents can have their own issues on occasion.

It tends to provide a better quality of analgesia, along with a patient who has an entirely unclouded sensorium. That super lucid patient can now become a really crucial agent in clinical assessment. At the same time they can be more aware of what’s going on without the distress of pain. I’m inclined to think that a patient who can be reassured and coached effectively through each step probably has a better journey in the long run than the one dozing in and out a bit. I’ve seen patients with both femurs smashed up cracking jokes in the emergency department with their doctors and nurses thanks to functioning nerve blocks.

So is the issue that the technique seems too forbidding? That hardly seems possible.

The Nuts and Bolts

The fascia iliaca technique was first described in the literature by Bernard Dalens, a paediatric anaesthetist. He and his colleagues had gone back to the anatomical drawing board in search of a better femoral nerve block than the ‘3-in-1’ technique. It arose from paeds anaesthesia for a pretty good reason – Dalens was after a block that would work in patients who couldn’t give you good feedback about experiencing paraesthesia, or for whom rationalising the sensation of nerve stimulation might be a bit much.

It’s a while back that this work appeared too – 1989. At the start of 1989, Milli Vanilli were still thought to be a legitimate music act and Rain Man won big at the Oscars. This is not a new technique.

In a comprehensive description of the anatomy involved (complete with radiographic demonstration of local anaesthetic spread) Dalens and crew also report success compared to the ‘3-in-1’ technique – 55 of 59 patients with a successful block of all the nerves they were aiming for (vs only 11 of 51 having block of all the nerve branches in the ‘3-in-1’ group).

They also reported higher first time success rates and less motor blockade. Sounds perfect.

It also just seems more sensible than looking for the femoral nerve. Why approach the nerve with a needle when you can produce the same block with the needle away from the nerve? Why be any closer to the vascular bundle than you need to be? I can’t figure out why you’d bother.

So what are the key points in the technique? (I start with an assumption that as much monitoring as possible is on the patient.)

1. Define the spot for the ‘X’ that marks the spot.

Join the anterior superior iliac spine and the pubic symphysis (draw a line if necessary). Divide it into 3 parts. The mark for where the outer third starts is your staging point. Now drop down a couple of centimetres. There’s your ‘X’. Want a double check? Feel for the femoral pulse. You should be at least a couple of centimetres closer to the edge of your (probably imaginary) bed.

2. Prepare the skin

You still have to be clean. It’s also nice to put a little bit of quick-acting local under the skin to make the rest more pleasant. So wait 1 minute.

3. Use the right needles

I think it helps to make a hole in the skin for the subsequent needle to work through. Sometimes the force required with the short bevel needle makes you really dive through the first ‘pop’ just by the effort to get through the skin. Everything is easier if that resistance at skin level is gone by using a standard needle first.

For the actual procedure, something with a short bevel. It’s the short bevel that lets you feel the two pops. The whole technique (when doing it by feel) relies on the two pops. The first is when you pop through the fascia late. The second is when you pop through fascia iliaca.

My other tips here – once the short bevel needle is through the skin, come right back to almost skin level. You don’t want any doubt as to which is the first pop. Second tip – steady pressure on the needle once you start. Steady pressure leads you to distort the fascia until you suddenly pop through. Then you rest for a second, start your steady pressure again and you’ll feel the sudden give more obviously. If you make short, sharp moves you can fool yourself into thinking you’ve had a pop.

4. Mix the drugs

This one isn’t from Bernard. For prehospital use you do want that block working quickly (that might be less relevant in theatres and maybe even ED). You also have that nagging worry about using solid doses of long-acting agents that might be a bit intractable if they find the heart and cause mischief.

There’s nothing that says you have to use the one agent. I tend to mix in some lignocaine with something longer acting in low concentrations. The longer-acting drug is worth it too – I’ve had patients with a fractured femur get all the way to their operation later in the day without any need for ongoing analgesia.

I'd choose 11 if I could.
I’d choose 11 if I could.

5. Turn up the volume

In the original paper, Dalens used 0.7 mL/kg for the under 20 kg child, working up to 15 mL for those in the 20-30 kg range, 20 mL for 30-40 kg kids, 25 mL for 40-50 kg and 27.5 mL for those over 50 kg (using 1% lignocaine with some adrenaline). The whole idea is spread through a plane, so more is better. I commonly think up to 1 mL/kg, with the local anaesthetic diluted to allow that volume. More volume guarantees spread without dropping speed of onset too much.

 

Things I don’t do? Well I don’t think using ultrasound adds anything in the prehospital or retrieval context. So I don’t do it. That said the description right here from NYSORA is pretty good.

I do still use it in some patients with other injuries – a block that works and takes away the pain of a femoral fracture, apart from being inherently good for the patient, will still decrease the overall need for analgesia because it’s like one big painful injury didn’t happen.

But What About the Prehospital Space

Well why wouldn’t we do it? Worried about local anaesthetic toxicity? Then use less of the drug. Worried about compartment syndrome? There’s no evidence that having a block changes how often that occurs or causes problems. What I think is pretty clear is that it’s entirely feasible for the prehospital environment.

It’s been described in the care of a 6 year old. Back in 2003 Lopez et al reported use in 27 patients prospectively and saw a big drop in pain scores by the 10 minute mark. 1 block didn’t work. A French group (well, in the abstract as my French isn’t quite that good) report   63 successful blocks in a total series of 107 (other techniques were on the table).

More recently, a group in the Netherlands looked at a process for training the local EMS-nurses in this technique. Their results? 96 of 100 patients had a perfectly working block.

So why isn’t everyone doing it? I couldn’t find good research on that. So maybe it’s just that we spend so much time talking about other options, we forget what is, at its heart,

Or maybe it’s just habit and we need to people to remember there’s nothing about being able to block rapidly firing signals along sensory nerves with drugs in the same loose family as cocaine that shouldn’t be considered sort of astonishing.

Maybe next time there’s a patient with a badly bent femur you could start with a simple question: can I block this pain?

(Pssst … you know the answer already.)

Notes: 

I did a second edit to add a little more description (paragraphs 2 and 3) in the “Use the Right Needle” section. I also added a paragraph to clarify why I’d choose it over the femoral nerve block just before launching into the list of technique tips. It’s the paragraph that starts with “It also just seems more sensible …”

The original Dalens paper is sort of a joy.

Here’s that letter regarding use in a 6 year old.

Here’s the Pubmed link for the Lopez paper.

Here’s the Pubmed link for the French paper.

And here’s the SJTREM paper where they trained up EMS-nurses.

Oh, and to really understand how much can be offered by good regional techniques in retrieval medicine, it’s worth looking up this account of a soldier injured in Iraq. They had most of a calf blown away. With the addition of two nerve catheters (lumbar plexus and sciatic) they had initial debridement and subsequent operations interspersed with multiple long flights to finally make it back to Washington via Germany. All with good pain relief.

The image in this piece is in the Flickr Creative Commons section and is unaltered from the image posted by amp.