Do you remember where you were in 2011 when the results from NAP4 came out? I do. I was doing some upskilling in anaesthesia in New South Wales and the results of NAP4 lead me (and I am sure, many others) to change my practice. It was about the same time that FOAMed was taking off, so there was a renewed enthusiasm to challenge current practices, question dogma and seek to be ‘better’. Even now, several years later, I find myself referring back to NAP4 to confirm data and inform research in my favourite topic – difficult airway management.
So I was kind of looking forward to NAP5 – the fifth national audit project of the Royal College of Anaesthesia and the Association of Anaesthetists of Great Britain & Ireland. This audit examined the issue of accidental awareness during anaesthesia. This is perhaps one of the most feared complications for an anaesthetist….and indeed for a patient. The possibility of being awake yet unable to move (due to concomitant administration of neuromuscular blockade) is terrifying.
Click HERE to access the NAP5 report
But the results of the audit have left me feeling a bit ‘Meh?’. There are 64 recommendations in the Executive Summary, but a quick read of them just confirms what I thought we already knew – awareness can happen and good anaesthetic practice (which is essentially what the 64 recommendations summarise) can help mitigate this.
Perhaps that is a bit churlish. Audit is a tedious but necessary part of medicine. To quote Karim Brohi from #smaccGOLD when talking on the introduction of REBOA to a trauma service “you HAVE to sweep the floor….only then can you innovate”
So what was the reported incidence of awareness in NAP5?
Thankfully awareness appears pretty rare in anaesthesia, with NAP5 suggesting a 1:19,000 anaesthetics overall. Not surprisingly the incidence is increased by 7.5x when neuromuscular blockade is used compared to when not. Having the patient swing at the anaesthetist during the procedure is a fair clue that they are awake, whereas paralysed patients can’t punch! Actually, that’s not strictly true – the isolated forearm technique is one way of screening for awareness – but the number of anaesthetists who use this is vanishingly small. Of course aware patients can mount other responses, such as increased heart rate, blood pressure etc – but then again, reliance on these is inaccurate and somewhat cruel.If you take GA as a “treatment” for unwanted consciousness and take awareness as “harm” then the NNT is 1.00001 & the NNH is 17,0000! [Dr John Berridge, Doctors.net.uk]
Incidence of Awareness in NAP5
~ 1:19,000 anaesthetics overall
(1:18,000 with neuromuscular blockade vs 1:136,000 without paralysis)
High risk areas included cardiothoracic (1:8,600) and obstetric anaesthesia (1:670).
YEP – THAT IS RIGHT – 1/670 in OBS ANAESTHESIA
(before any smart arse comments, they DID exclude those having their baby under neuraxial blockade alone – clearly these patients are conscious and aware).
I wonder if the possibility of drug error contributes? The NAP5 authors mention presence of “antibiotic syringe” as being a particular risk – all the more reason to push antibiotics as soon as decision is made to go to section, then induce with usual anaesthetic agents. Interestingly I’ve herd anecdotes that the Poms don;t use propofol much for obs anaes (it remains off-licence for obstetric use in the UK!) – the older specialists insisting on use of thio.
I can’t recall ever seeing thio used in obs anaes in Oz; another indiction of how much dogma needs to be lysed, particularly when there is potential for harm. Hard to confuse propofol with an antibiotic, much easier to confuse thio!
Other risks included :
OBESITY (I suspect underdosing of induction/maintenance agents)
USE OF THIOPENTONE (probably because of 500mg/vial insufficient dosing in the lardy and possible use as bolus vs titrated dosing at induction Another thought is that propofol has some amnestic effect, so may confound patient recall of awareness when receiving thiopentone vs the Jackson Juice).
USE OF NEUROMUSCULAR BLOCKADE – amazingly it seems that many anaesthetists aren;t using nerve stimulator TOF intra-operatively. Interesting. Maybe I am obsessive about this?
Listen up emergency and critical care docs : Induction, Emergence and TIVA are particular risks
Other high risk stages of anaesthesia include the dynamic phases – namely induction and emergence. NAP5 suggests that 2/3rd of reported awareness episodes occurred during these phases. Again, not surprising as this is when a failure to establish post-intubation anaesthesia, accidental disconnections or residual paralysis on extubation are most likely.
How is those relevant to critical care and emergency clinicians? well, we all obsess about airway management, best choice of induction & paralytic agent (answer = “rocketamine”)…but we may become complacent once the ETT is passed and forget to establish quickly a post-intubation sedation plan. Even if we DO, infusions can be disconnected, pulled out – or, worse still, sedation may be inadequate for the time when your roc is still effective. Prehospital and ED doctors need to be as vigilant for awareness as anaesthetists in theatre – perhaps MORE SO as our patients are at risk.
“The post-intubation phase is a time of particular risk – the patient has been induced with ketamine, paralysed with rocuronium & tube placed without hypoxia or hypotension. Failure to ensure adequate ongoing sedation may lead to accidental awareness in the post-intubation paralysed patient. Be vigilant!”
Of particular interest to me was the fact that accidental awareness was more than twice as likely during total intravenous anaesthesia as when using volatiles; again, not surprising as the latter allows end-tidal volatile monitoring. An extra risk was TIVA using non-TCI techniques eg: intermittent manual bolus of agent, fixed-dose regimens etc. rather than the established TCI techniques available on sophisticated pumps.
“When transferring patients, whether it be from ED to CT, from OT to ICU or from Dingo Creek to tertiary centre as an aeromedical retrieval, this is when patients are at most risk”
This is a problem and something that all involved in management of critical patients should consider – namely that TRANSFER OF PATIENTS IS A RISK FOR AWARENESS.
What to do with the data?
The NAP5 data does give us up-to-date numbers for the incidence of awareness and I will use these in explaining risks to my patients, as I already do. Indeed it suprised me that one of the NAP5 recommendations was that :
“Anaesthetists should provide a clear indication that a pre-operative visit has taken place, identifying themselves and documenting that a discussion has taken place”
Doesnt eveyone already do this? Apparently not – whilst here in South Australia there is a separate anaesthetic consent form, there were none when I was in NSW (this may have changed). Colleagues in the UK seem content to allow the surgeon to consent for the procedure – whilst I can undestand that the gynae reg can consent for the surgery, I really dont see how he/she can adquately explain the anaes risks. But I digress…
But – what about those fancy BRAIN WAVE MONITORS?
Some of the important questions remain unanswered….we’ve had new anaes monitors rolled out into country, apparently on the pretext that depth of anaesthesia monitoring is mandatory. So someone ordered a bunch of machines with BIS monitoring. BIS or bispectral index is one form of proprietary EEG (pEEG) monitor, marketed as giving an indication of ‘depth of anaesthesia’. My preference is to use measurement of end-tidal anaesthetic gas to decide if there is sufficient volatile on board.
At present, use of proprietary EEG monitors is NOT considered a standard in anaesthesia in Australia. Moreover there is some evidence that reliance on a particular pEEG number to decrease concentration of volatile is more likely to cause accidental awareness (fully awake BIS = 100, brain dead = 0. Sort of. It’s a bit more complicated, but you get the gist).
Like many others, I remain unconvinced of the role of BIS during general anaesthesia with a volatile agent.POP QUIZ – HOW DO YOU ‘ZERO’ THE BIS MONITOR? ANSWER – USE THE ORTHOPAEDIC REGISTRAR
Again, perhaps the most risky aspect of anaesthesia is when using intravenous anaesthetic agents in the face of neuromuscular blockade. This is particularly pertinent to my current role in retrieval, where it is not uncommon for critically unwell patients to be induced with ketamine, paralysed with rocuronium then placed onto a maintenance infusion (propfol, fent/ketamine, morph/midaz etc) – if there is an omission of post intubation sedation, an accidental disconnect or even an under-dosing, then awareness under paralysis is a real possibility. Where possible paralyse then allow to wear off and use appropriate ventilator settings to allow spontaneous ventilation in transit.
Which begs the question – should the role of pEEG monitoring be targeted to those patients who are paralysed and undergoing TIVA – typically retrieval & some ICU patients? I am not aware of a transport monitor that allows measurement of pEEG. Should we be using it for some of our intubated and ventilated patients? Interested in others thoughts on this….
And finally – a checklist proposed as the cure to reduce accidental awareness!
The authors also propose use of checklists during ‘high risk of awareness’ occasions (such as transfer of patients). Moreover, the NAP5 authors recommended :“the use of an ‘anaesthetic checklist’ (easily integrated with the World Health Organisation Safer Surgery checklist) to be used after transfer of patient, to prevent incidents of awareness arising from human error, monitoring problems, circuit disconnections and other ‘gaps’ in delivery of anaesthetic agent”
Now it is no secret that I am a fan of checklists – I argued passionately (and a little rudely) for their use by airway experts at smaccGOLD – but I would also advice caution in their use
Whilst the WHO surgical checklist is lauded as reducing complications, this is utterly dependent on successful implementation. Sadly for many units the WHO checklist has been opposed from on high, without opportunity for team buy in or local modification. In these circumstances, a checklist can become worse than useless – it can be a danger. We’ve all got anecdotes of the checklist being completed after induction of anaesthesia, of the whole process being reduced to a pointless tick-box hurdle to be rushed through, rather than a cognitive rallying point.
We MUST be cautious of checklist fatigue.
As I said at smacc, pehaps their use is best reserved for routine only when there is full team buy in and the checklist is implemented by the frontline users – not imposed from on high. The benefits of a checklist in anaesthesia crisis are predominantly through a challenge-response of ‘have you considered X‘ rather than a cookbook ‘the next step will be to do Y‘ approach.
So is NAP5 a gamechanger?
I don;t think so. Reading the recommendations in the Executive Summary reads more like a description of how a good anaesthetic should be given. I hope I am not alone in reading the 1-64 recommendations and going “yep – do that – and that…”
I don’t think it really addressed the issue of pEEG monitoring. Intuitively they may seem ‘sensible’ but I maintain that there use is probably best confined to the paralysed patient on TIVA.
Are there lessons here for emergency doctors, intensivists and retrievalists (not just anaesthesia)? Absolutely. It may be that awareness of ‘awareness’ amongst emergency clinicians is less heightened than the archetypal OCD-anaesthetist….and yet our post-rocketamine patients are at particular risk.
Be alert to the risk of awareness when managing a patient who has been paralysed and is being maintained on an infusion to keep them asleep.
I will leave the last word to that esteemed Professor of Hogwarts, Prof Mad Eye Moody :
…since posting, the Daily Mash have taken up the results of NAP5 – and twisted them