Well after a rather long absence (involving certain exam distractions) we’re finally back in action here, and the timing couldn’t really be better with the recent publication of the 5th National Audit Project (NAP-5). In a similar manner to the previous NAPs, this project took a national look at a specific area of anaesthetic practice, in this case ‘Accidental Awareness under General Anaesthesia’ (AAGA). The summary articles have been published in Anaesthesia journal (and I believe in the next BJA), as well as the full report available through the NAP homepage, all of which are freely available if you haven’t had chance to view them yet. As such, I thought it’d be worthwhile to have a quick flick through their findings and see what we can take from the audit back to our daily practice.
What've They Done?
Well if you’ve not come across the NAP concept before, it involves looking at a specific (often rare) aspect of anaesthetic practice over a long period of time through the UK to try and get a better understanding of its incidence and contributing factors. Previous projects have looked at complications of neuraxial blockade and difficult airways, but this time it was the turn of AAGA.
Similar to previous NAPs they used local co-ordinators at each hospital through the UK to collect and feedback any reports of AAGA over a period of 12 months (1st June 2012 – 31st May 2013). This was then compared against a ‘denominator’ survey that attempted to get an idea of the total number of anaesthetics being performed. Reporting of awareness was a completely passive process (i.e. patients weren’t specifically questioned about it) though there were efforts to increase the publicity of the study to ensure that other non-anaesthetist healthcare professionals that received reports of awareness (e.g. GPs, psychiatrists) might feedback to the local co-ordinator.
Similar to previous NAPs they used local co-ordinators at each hospital through the UK to collect and feedback any reports of AAGA over a period of 12 months (1st June 2012 – 31st May 2013). This was then compared against a ‘denominator’ survey that attempted to get an idea of the total number of anaesthetics being performed. Reporting of awareness was a completely passive process (i.e. patients weren’t specifically questioned about it) though there were efforts to increase the publicity of the study to ensure that other non-anaesthetist healthcare professionals that received reports of awareness (e.g. GPs, psychiatrists) might feedback to the local co-ordinator.
What Did They Find?
A total of 300 reports of awareness were made during the yearlong data collection period. Analysis of these reports resulted in an impression that 141 (47%) represented cases that were certain/probable/possible in probability, with a varying number assigned to different categories based on lesser degrees of certainty. This included 32 (11%) where the reports were from a sedation rather than a general anaesthetic procedure, 12 (4%) being determined as unlikely to represent AAGA, and 89 (29%) being impossible to assess in probability due to the nature of the report and information available.
The baseline activity survey provided an estimate of 2.8 million anaesthetics given during this period to act as the denominator. As such, this gave an approximate incidence of awareness of about 1 in 19,000 anaesthetics (depending on the strictness of inclusion criteria). Even if the most pessimistic interpretation of the data was employed (with all the reports of indeterminable nature being assumed to be definite awareness) this worked out at an incidence of 1 in 12,000 anaesthetics.
These numbers do seem some way from previously quoted values (in a good way), though I think it is upon closer inspection of the events where some interesting points can be found.
The baseline activity survey provided an estimate of 2.8 million anaesthetics given during this period to act as the denominator. As such, this gave an approximate incidence of awareness of about 1 in 19,000 anaesthetics (depending on the strictness of inclusion criteria). Even if the most pessimistic interpretation of the data was employed (with all the reports of indeterminable nature being assumed to be definite awareness) this worked out at an incidence of 1 in 12,000 anaesthetics.
These numbers do seem some way from previously quoted values (in a good way), though I think it is upon closer inspection of the events where some interesting points can be found.
Neuromuscular Blockade
Neuromuscular blockade (NMB) is the key risk factor involved in AAGA, as could have probably been guessed. That rocuronium is going to stop your patient providing constructive criticism to you on the depth of their anaesthetic so it’s no wonder that 93% of the cases involved NMB. Particular facets that they drew out were that lack of NMB monitoring and reversal contributed to episodes of awareness during emergence, a scenario that seems relatively avoidable. That said, avoidance of reversal agent and indeed nerve stimulation is a scenario I see not that uncommonly, instead basing the degree of reversal on the duration since any NMB agent was given. I suppose this isn’t outrageous in many circumstances, especially in experienced hands, but I feel that waking up a paralysed patient might not look great through the retrospectoscope just for saving a few seconds not twitching them. It only takes a few extra seconds (especially because the nerve stimulator is always where it should be and easy to find….). NMB was also noted as a higher risk throughout all the other phases of anaesthesia as well. Combination with a total intravenous anaesthetic (TIVA) was an area noted for potential risk, with the problems of cannula disconnection or 'tissuing', as well as the lack of commonly employed depth of anaesthesia monitoring in the same way that end tidal vapour concentration is monitored.
Timing
A similar lack of surprise was encountered when it emerged that the highest incidence of awareness was during the dynamic phases of induction and emergence (65%). The nature of induction also played a role, the main culprit being rapid sequence induction where a number of factors were implicated, including lack of opioids, excessively cautious dosing, and prolonged difficult intubation without provision of extra anaesthetic agent. This risk period around induction extended through the initial period of patient transfer into theatre where the gap between induction agent and vapour maintenance agent presented a possible window for AAGA. Indeed forgetting to turn the vaporiser on at all after transfer was implicated in some cases, identifying that this period of time remains an important one for potential error (The trust I am at currently employs a ‘vapour on?’ check as part of the ‘time-out’ check-list – a simple addition that seems to provide a extra layer of safety netting for this).
Syringe Swaps
Though these are the horror stories that get heard (and run through my mind during all drug preparation), the syringe swap/drug error cause accounted for just 7% of the AAGA episodes reported. That said, these appeared to be (unsurprisingly) responsible for the greatest degree of distress and long term impact on patients compared with others. The potential for a cefuroxime-based anaesthetic already guides my current practice with me keeping antibiotics well away from my thiopentone. Similarly, every NMB gets an instant saline flush to stop it saying hello again on the ward later. These episodes appear to be more a result of multiple factors colliding to produce the event, such as distractions at crucial moments.
Sedation
The authors analysed the incidents of AAGA whilst receiving sedation separately from the rest of their analysis for the fairly obvious reason that they weren’t actually receiving a general anaesthetic. The authors highlighted that, despite our own understanding of what sedation is and how it differs from a general anaesthetic, the unanticipated awareness and any associated pain/discomfort, was particularly distressing for the patient if complete lack of awareness was expected by them. Indeed the main point they raised was that miscommunication was deemed to be the prime contributory factor in the majority of cases reported. I suppose if you are expecting a nice gentle sleep, full memory of your gastroscopy will not be recalled fondly. I do feel that when I consent for sedation I am realistic about what the patient can expect, but this brief consent process may still be running against the patients understanding and expectation and so produce problems.
There are many more facets of awareness and risk factors that I won’t transcribe here for the sake of brevity, but the very high obstetric incidence is particularly notable, though many of the risk factors seem to be a combination of several non-obstetric ones in one big helping (lower/different dosing, larger patients, difficult airways and emergency situations). I'm not quite convinced that the choice of drugs plays a role in awareness, rather that they are an artefact of the scenarios they are most commonly used (thio in RSI), but it does call for a pause for thought as your calculate your thio induction dose.
There are many more facets of awareness and risk factors that I won’t transcribe here for the sake of brevity, but the very high obstetric incidence is particularly notable, though many of the risk factors seem to be a combination of several non-obstetric ones in one big helping (lower/different dosing, larger patients, difficult airways and emergency situations). I'm not quite convinced that the choice of drugs plays a role in awareness, rather that they are an artefact of the scenarios they are most commonly used (thio in RSI), but it does call for a pause for thought as your calculate your thio induction dose.
Personal Thoughts
I must admit that initially my reaction was one that seems to be echoed by what I have heard from others I have spoken to and reactions I have seen elsewhere; rather underwhelmed. The results showed that this is an adverse event that is actually even rarer than we thought, and the 64 recommendations are all fairly obvious and in line with what I imagine is most anaesthetist common practice. However, after some digestion I felt there were two really important points to take away from NAP-5
Firstly, we are generally doing a great job with regards to AAGA. As one of the most feared complications for patients and anaesthetists, the incidence is reassuringly low. Though it might be less headline grabbing than the converse, audits confirming good care are just as important as those demonstrating gaps.
Secondly, and I think most importantly, the recommendations highlight an important tenet of anaesthesia (despite my facetious remarks for comic effect). It’s not about the fancy kit, dramatic procedures and experimental techniques; it’s about being meticulous with the basics. Humans make mistakes and always will, and it is essentially a numbers game. I’ve started viewing more and more of my practice as windows for different slips and lapses to creep in and risk affecting my patient. We can probably get away without twitching patients most of the time, but that 1 in 19000 ratio gets smaller. Giving reversal agent is a bit of extra faff, but that ratio gets smaller still. Premixed cefuroxime next to my thio is unlikely to cause problems, but my odds are getting pretty small now. We’ve got a margin for error with awareness most of the time, but I like as many safety nets as I can have, and I doubt our patients would object to this. And I think that is what NAP-5 is all about.
Firstly, we are generally doing a great job with regards to AAGA. As one of the most feared complications for patients and anaesthetists, the incidence is reassuringly low. Though it might be less headline grabbing than the converse, audits confirming good care are just as important as those demonstrating gaps.
Secondly, and I think most importantly, the recommendations highlight an important tenet of anaesthesia (despite my facetious remarks for comic effect). It’s not about the fancy kit, dramatic procedures and experimental techniques; it’s about being meticulous with the basics. Humans make mistakes and always will, and it is essentially a numbers game. I’ve started viewing more and more of my practice as windows for different slips and lapses to creep in and risk affecting my patient. We can probably get away without twitching patients most of the time, but that 1 in 19000 ratio gets smaller. Giving reversal agent is a bit of extra faff, but that ratio gets smaller still. Premixed cefuroxime next to my thio is unlikely to cause problems, but my odds are getting pretty small now. We’ve got a margin for error with awareness most of the time, but I like as many safety nets as I can have, and I doubt our patients would object to this. And I think that is what NAP-5 is all about.
Well thanks for reading and I hope you found it interesting. Hopefully there shall be less of a delay until the next post but in the meantime please let me know your thoughts on what NAP-5 means for you and your practice. Are there any habits or routines that you build in to you everyday practice to minimise risk of awareness and how do you find it maintaining these consistently? I'd be very interested to hear.
Tom Heaton
Tom Heaton
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