Probably one of the greatest benefits of being a trainee is the chance to rotate around different departments, different hospitals and work with different consultants. The variations in anaesthetic technique can be quite significant, and there always seems to be some aspect of it that I can take away for my own practice, either positive or negative. As such, I came to be working with a consultant I haven’t had chance to work with before and witnessed a fascinating piece of practice that I was amazed I had never seen before. Basically, every patient that got intubated had several sprays of lidocaine on their larynx at initial laryngoscopy. The impact on the extubation of these patients was quite remarkable. Instead of coughing, bucking, thrashing around and generally going bright red (not that all my extubations are like that), they opened their eyes, nodded in response to questions and were just generally very happy with this piece of plastic in their trachea (caution: case series was only an n of 2). To say I was impressed was a bit of an understatement. However, the questions quickly followed. The most obvious had to be; why doesn’t everyone do this? What’s the catch? What are the side effects and risks? It crossed my mind that this nicely numb larynx might not deal especially well with that chicken sandwich it comes across when back on the ward. My consultant hadn’t experienced any adverse events as a result of this (and used it frequently) and even described a few papers that had looked at this topic. Tempering my initial excitement with some scepticism I decided it would be worth a bit of research to see what the literature threw up.
As such we have ended up with this post, looking at one particular paper on the subject. After a few pubmed searches, this paper in Anesthesia & Analgesia surfaced:
Laryngotracheal Topicalization with Lidocaine Before Intubation Decreases the Incidence of Coughing on Emergence from General Anaesthesia.
It seemed a suitable starting point to build on my ‘n of 2’ personal experience to see if there was evidence of a similar degree of efficacy. A double blinded RCT in a major paper seemed a great place to start with this, so let’s have a look at it.
As such we have ended up with this post, looking at one particular paper on the subject. After a few pubmed searches, this paper in Anesthesia & Analgesia surfaced:
Laryngotracheal Topicalization with Lidocaine Before Intubation Decreases the Incidence of Coughing on Emergence from General Anaesthesia.
It seemed a suitable starting point to build on my ‘n of 2’ personal experience to see if there was evidence of a similar degree of efficacy. A double blinded RCT in a major paper seemed a great place to start with this, so let’s have a look at it.
What's It About?
As the authors state at the start, coughing during extubation can cause problems other than just make you look like a bit of a rubbish anaesthetist. With an incidence of up to 96%, the coinciding hypertension and tachycardia are something that I’m sure we see fairly regularly. The authors have put together a nice little placebo controlled, double blinded, randomised control study to see whether spraying the airway with some local at the start improves this. They have selected 50 ASA 1/2 patients undergoing fairly straightforward, and importantly fairly short, elective gynaecological procedures. After excluding some fairly reasonable groups (regurgitation risk factors, smokers, respiratory tract infection) they provided a fairly standardised general anaesthetic. They were randomised to receive 4ml of either normal saline or 4% lidocaine via a specialised endotracheal injector (LTA 360 kit, which I’ve never heard of). The anaesthetist was blinded to what they were giving, the rest of the operation went on as normal and the patient was woken up, again all in a fairly standardised way. An independent, blinded observer graded the degree of coughing at extubation and in the post extubation period on a 3 level scale (mild, moderate, severe).
What Did They Find?
Well the results look pretty impressive. 26% of the lidocaine group coughed before extubation compared with 70% of the placebo group. The difference looked just as good in the post extubation period, with just 4.3% (1 patient) of the lidocaine group coughing compared with 30% of the placebo group. A quick through look the patient demographics doesn’t reveal any obvious differences in important stuff, such as opioid usage, which is as you would expect with the study design. Pretty significant results.
Is It Any Good?
As a quick answer; yes. The design of the study was generally very well done, and the authors have ticked off all those favourite buzzwords; placebo controlled, double-blinded, RCT, Nice! Even though it’s only looking at 50 patients, they’ve done their power calculation at the start using numbers that look very reasonable. Indeed they’ve gone for a 50% relative risk reduction which isn’t trivial. As mentioned above the standardisation of the anaesthetic looks like a good balance of practicality and prescriptiveness. There were a few exclusions from the initially recruited patients but these are all clearly explained and justified.
The outcome was done by a blinded, independent observer, and though I’m not completely convinced about the rigour of their categorisation, it seems passable and they have at least been clearly described (the duration of bouts of coughing). Is this a valid way for categorisation the severity of coughing? I’m not sure, but as I said it seems reasonable. As the authors note, it is a scenario where there is likely to be some variation in the other components of the anaesthetic that might also have an influence on the extent of coughing, but you would expect that having it double blinded and randomised would negate any confounding role that this may play.
The outcome was done by a blinded, independent observer, and though I’m not completely convinced about the rigour of their categorisation, it seems passable and they have at least been clearly described (the duration of bouts of coughing). Is this a valid way for categorisation the severity of coughing? I’m not sure, but as I said it seems reasonable. As the authors note, it is a scenario where there is likely to be some variation in the other components of the anaesthetic that might also have an influence on the extent of coughing, but you would expect that having it double blinded and randomised would negate any confounding role that this may play.
Final Thoughts
Well overall it looks like this trial adds a bit of weight to what I witnessed the other day. This seems pretty decent evidence that topical lidocaine does reduce the adverse physiological response to extubation, at least with respect to the coughing. And the impact seems pretty substantial too. This has therefore gone some way to answering the first question I had about this technique; it’s effectiveness. However, I was so impressed with the transformation that I had witnessed in my 2 patients that this wasn’t something I was doubting. I was more concerned about possible adverse effects from such a technique. Unfortunately, no matter how well conducted such a trial is (and it was pretty good), having only 50 patients is nowhere near enough to start to answer this question. Indeed I am trying to think of what sort of trial design would be needed to achieve this given the presumed rarity of such adverse events. I’m thinking it’s going to have to be pretty large though and, after a quick flick through my initial Pubmed search results, I'm not sure it has been done.
Bringing it all together, I can think of three components to this technique. Firstly, is it effective? This paper seems to provide some strong weight to this being so, and there are few other trials with similar results. Secondly, is it beneficial? Well other than making you look pretty awesome at extubation, there are a few clinical scenarios where a smooth extubation will definitely be benefical. Surgical and patient factors that will benefit from a none-hypertensive, tacchycardic, raised intra-thoracic/cranial/ocular pressure scenario are plentiful. But how does this balance against the third component; is it safe? The answer to that doesn’t lie within this paper, or the others I have looked at so far, and I would personally struggle to even begin to estimate it. Whilst definitely interesting, an interesting idea is all it will remain for myself at the moment. Hopefully I shall come across a paper that sheds some more light on this final aspect that may change things.
Thanks again for reading. Please let me know if this is a technique you use regularly or if there are any papers you have come across that have looked at this safety profile. I’ll try add a bit more if I unearth any new ones. Until then, thanks once again.
Tom Heaton
Bringing it all together, I can think of three components to this technique. Firstly, is it effective? This paper seems to provide some strong weight to this being so, and there are few other trials with similar results. Secondly, is it beneficial? Well other than making you look pretty awesome at extubation, there are a few clinical scenarios where a smooth extubation will definitely be benefical. Surgical and patient factors that will benefit from a none-hypertensive, tacchycardic, raised intra-thoracic/cranial/ocular pressure scenario are plentiful. But how does this balance against the third component; is it safe? The answer to that doesn’t lie within this paper, or the others I have looked at so far, and I would personally struggle to even begin to estimate it. Whilst definitely interesting, an interesting idea is all it will remain for myself at the moment. Hopefully I shall come across a paper that sheds some more light on this final aspect that may change things.
Thanks again for reading. Please let me know if this is a technique you use regularly or if there are any papers you have come across that have looked at this safety profile. I’ll try add a bit more if I unearth any new ones. Until then, thanks once again.
Tom Heaton
References
- Anesthesia & Analgesia; Laryngotracheal Topicalisation
- Medical Science Monitor: Local Aiway Anaesthesia
Image courtesy of freedigitalphotoes.net/David Castillo Dominici
RSS Feed
