hi everyone this is Lahiru from abc's of anesthesia now today i'm going to be talking about
one of those rare complications that pretty much most of my patients would be afraid of and this
is being awake during this surgery or anesthesia or formerly known as accidental awareness under
general anesthesia or aaga so let's get started so being awake under general anesthesia during
operation is obviously ridiculously scary as a concept um but it's also one of those things that
seems to be more feared than even death under anesthesia and so it really matters and a lot
of the time this is scary because you see stuff in the popular media and in movies and tv for example
the movie awake by joby harold starring hayden christensen and jessica alba this is a movie
about someone who is awake during some major heart surgery and again it's a thriller it's got a whole
bunch of stuff that's really complex in it and you know this is the kind of fears that patients
might have when they approach me and are about to have their anesthetic now obviously there's a
huge spectrum of what anesthesia is so when we're talking about awareness under general anesthesia
we're not talking about remembering things during those minor procedures you know like sedation
for lumps and bump excisions or just for local anesthetic doing a simple operation
and it's not really talking about as you get out of your anesthetic you might remember
something like having a breathing a breathing tube or something in your mouth that's really
not awareness as we describe it and that's why i often mention to patients under general anesthesia
that as they're waking up as the surgery is complete they'll feel something or they might
feel something and they might remember something in their throat and that just means that we're
pulling out the tube or the breathing device when they're awake and ready to breathe for themselves
now i really think stats are important i think it's really important to know as a clinician or
as even a patient how common are these risks you know this is something that's obviously serious
is this likely to happen to me and there's a fantastic project the national audit projects run
by the national health service um in the in the uk they do some amazing massive series uh where they
look at all these rare adverse events and one of those is awareness under general anesthesia
and so the nap 5 study which i'll put a link to in the story nurse kind of gives us some really good
data and also some really great recommendations as well as the things to look out for and how
to prevent it and so i'll be referring to the stats from this particular project the national
audit project which is run by the nhs in the uk and then the nap studies they're fantastic
they look at large numbers of patients over a few years to see what happens with these rare events
whether it's awareness airway problems anaphylaxis etc so i'll be referring to this document um
and again it's really important to know this data because then we can have something that
we can actually refer to when we're consenting to patients and seeing what the actual risk is so how
common do you think awareness under general anesthesia is so it's about on average one
in twenty thousand now this is more for paralyzed patients in this study about one in eight thousand
and roughly speaking when you've seen when we've seen stats and series of you know when
this occurs it's always in the realm of around one in ten thousand or even even more so in an
unparalyzed patient the rate of awareness under general anesthesia is about one in 136 000 so you
know most times when you're having an anesthetic it is very unlikely that you're going to be aware
and that's one of the most reassuring things so look i'm giving you a lot of stats but what do i
do with these statistics now when i'm trying to make a decision you know one in twenty thousand
one in a hundred thousand it really doesn't make much sense to me so i really wanna know what does
that mean to me as a person and how do i make a decision based on these stats and what a lot of us
will refer back to is that what is something that we do every day or you know in daily life that we
do without even questioning and you know can we anchor this risk and compare it to something that
we do in daily life so a lot of people would talk about the risk of dying in a car accident now the
risk of dying is roughly around the one in ten thousand mark i think in the uk and australia
that number might fluctuate but it's roughly you know if you drive a car for a year then your
chance of having you know dying in a car accidents around one in ten thousand and so if i think about
the risk of awareness being one in twenty thousand this is obviously safer than even driving a car
therefore if you drive a car without thinking having undergoing an anesthetic doesn't seem to be
the highest risk now obviously it's one of those things where when you're balancing the risk you
might have a very specific circumstances always have your own personal circumstances in mind and
always talk to your surgeon and your anaesthetist because there might be other factors about the
surgery and about yourself that make it more or less risky so again absolutely go to your treating
team to make sure that you're making the right choice so if i am afraid of having this awareness
on a general i see how do i make a decision and again i think the most important thing is to go
to your surgeon and this find the right balance what is the risk of having awareness or the risk
of something bad happening under anesthesia for that particular surgery in your circumstance
and then think about whether that's worth it for you for example not having the operation is its
own problem are you going to be willing to suffer through whatever complication or whatever problem
you have and not have surgery because you're afraid of a 1 in 20 000 chance of having something
and so i think these are the questions you need to ask yourself and hopefully with your doctor
and supervising team you're able to make a really good decision so i mean the important thing to
know is that no matter what we do in life there's always a risk whether it's you know driving a car
flying overseas you know going to work every day or maybe even just eating certain foods that are
allergenic so whatever we do there's risk and it's up to you to really make a decision and be
guided by good evidence to make a good decision in your circumstance so a lot of people might not
really understand what exactly happens when you go and anesthesia and you're having your surgery
and i thought i'd just clarify that so anesthesia is actually you know really complex medicine where
you're taking a combination of medications to make sure that you're pain-free that you don't remember
anything or they call it hypnosis and that you are still enough for the surgeon to operate
so we talk about the anesthesia triad being you know analgesia or pain relief making sure you're
not you know uncomfortable that you don't remember anything hypnosis and that you're still enough
for the surgery to occur safely which is paralysis so when i think about anesthesia each procedure
that you have needs a combination of these for some for example some procedures just need a
bit of analgesia for example if you're having a little lump removed from your you know like a mole
removed from your hand you might just need some local anesthetic in the skin and that provides
you with analgesia but you remember everything and you're not paralyzed the surgery is small and
doesn't require that sometimes you might just need a bit of sedation for example if you're having a
gastroscope so that's where they put a telescope down your throat you might need a bit of sedation
with something like midazolam or propofol which essentially mean that you don't remember much but
you might remember some things but again because it's only a minor procedure that doesn't have any
massive operative problems it doesn't have a big incision you probably don't need large amounts of
analgesia and you definitely don't need paralysis for most of those procedures and then there's
other operations that are really big and you know need require a full general anaesthetic for
example if you're having your gallbladder taken out or having a bowel operation cardiac surgery
a whole bunch of other major operations you need a lot of analgesia you definitely don't want to
remember all that stuff happening to you and you need to be paralyzed to make sure you're
not moving inappropriately for the surgery so then my job as a niece is really to take
the surgery and consider that look at you as a patient and any medical problems you might have
and including things like you know your age how much you weigh your gender and a few other factors
you know your heart and lung function and then i can tailor the anesthetic for you for that surgery
and again for that surgery it could be anywhere from just a bit of light anesthesia where i'm not
giving you too much anesthetic because you don't need it to higher deeper levels of anesthetic
until i get to a full general anaesthetic and there's a spectrum that you could be on and the
anaesthetist will tell you about that and that's part of our job being able to communicate that
now you know to be in an eastern australia you do you know four to six years in medical school
two to three maybe even longer of just general medicine and then after that you do five years
of specialty training so there's a lot of work that goes into just balancing and knowing how
to make sure these medications are working in the right way and that we treat the problems of those
medications as well i've got lots of videos on the channel just about that so let's say i do a
standard anesthetic for a gallbladder operation um where you know someone's got a biliary colic
and they need their gallbladder taken out so essentially most people would give a dose of
profile which gets you off to sleep it'll give you some analgesia like fentanyl and then also
give you a paralytic now after that point those medications are working for a certain period of
time to keep you asleep i might keep giving you perform through an infusion driver or run some gas
and volatile gas and measure that at the right level to make sure you're asleep
then i you know make sure once you're at the absolute right level then the surgeon usually
says hey ready ready to start and if everything's absolutely fine i'm looking at my monitors making
sure that everything's good then i say yep ready to start and so only when you're absolutely ready
does the surgeon start with the with the procedure so what do a nieces do to try to prevent awareness
under general anesthesia so what we do we look at a whole bunch of things a whole bunch of factors
for example we know your circumstance as a patient and we know what the surgery is so i'll tell my
anaesthetic based on your circumstance and then i'll look for lots of clinical signs for example
i'll look to see if you're flushed if you're sweating or you have tears around your eyes that's
one of the kind of weaker signs that you might see if someone is aware other things will be monitored
for example your heart rate and your blood pressure now those are monitored continuously
throughout the whole time and i'll be there for every moment of that surgery to make sure that
everything is you know going well and so if the heart rate rises the blood pressure rises that's
something we'll always check to make sure that you know you're absolutely deep enough with the
anesthetic if the patient isn't paralyzed then you might see an increase in the respirator and again
as soon as that happens you know that the patient might need a bit more analgesia or anesthetic as
well so again lots of signs tell you what's going on now one of the things that could happen is the
patient could move and often wrongly the whole theater team doesn't understand that movement
is separate from consciousness so the body has a lot of reflex movements that can occur
but this doesn't mean that the patient's conscious so if movement happens it's often a really good
precursor that the patient isn't deep enough and that's not a problem you just have to give
more anesthetic and try to make sure that the patient is deeper next time so you know movement
during surgery occasionally happens it probably shouldn't but you know if it does happen you just
need to give more anesthetic to make sure the patient doesn't move but just remember that's
most likely just a reflex movement and doesn't mean that the patient's actually conscious
because they've already got enough anesthesia to be unconscious this is one of the beautiful things
about medicine and the body's physiology is that the amount of anesthetic to make sure that you're
asleep is probably a bit less than the amount of anesthesia that you require to stop moving
so that's just one of those nuances to make sure that you know we've got a safety margin with that
as well now one of the other things that we do is have awareness monitors now probably one of the
most tried and tested awareness monitors is having a really good level and tidal volatile gas so
your operation conspicuously involves how fast you know how much is going into the pectin and
also how much is coming out that's called the end concentration of volatile gas which is the
end tidal volatile concentration really just means that the end of a tidal volume so as you do that
that's your tidal volume a gas monitor measures that concentration and gives you a reading
so your training which is called min concentration or mac and as long as the mac is high enough
it means that you probably aren't to remember what's going on you know i've always got to
clarify that that's probably not but absolutely every single thing but in big stuff because it
shows that's a pretty safe level of anesthesia to prevent any kind of awareness so volatile gas is
great this is really easy to measure because we've got we've got the gas analyzers so that's a really
good way of making sure that your patient is not going to be aware the other thing you might be
doing is running a propofol infusion so instead of having a gas keeping your sleep you'll have
liquid through a drip keeping your sleep now the problem with that is it you know you can't
measure how much is in the blood very easily and in real time like with the volatile gas
measurement and analyzers so that means that we use these very special pumps to dial up a
concentration to be in your plasma and using some fancy mathematical model modeling it can
titrate how much liquid goes into your body to keep you at a certain
and that's not absolutely perfect because all you're doing is you're doing some fancy maths
to make sure that what you're doing is correct but there's always a chance that things could get dis
disconnected or maybe this patient needs more or maybe their physiology is different so in that
sense it's more risky for awareness on a general anesthesia to run the liquid than it is to run the
gas and one of the other monitors that has kind of come out pretty new is called the entropy monitors
and these awareness monitors include entropy as well as biz now these are both trade names for the
particular monitor and i'll do a demonstration soon as well so this particular monitor
this is a biz module i'm just going to plug this cable in into this little spot over here
so this is the monitoring device and there's the particular one we use
there's another one called entropy as well um so what you do essentially open the pack
and you get this little device that looks like this and this just
sits across the forehead and i'll just demonstrate that now
now if you're a patient what you might find is that people will just do this and just
clean the surface of your skin before they apply it
now it's a little bit prickly you'll feel someone just pushing down lightly on this
and then hooking it up
to this monitor over here and so you'll see that it says checking sensor
and that automatically does that
and you'll get these ticks and then it'll read out what your reading is now most of the time
you'll see that that's a modified or you know summarized eeg
reading you'll take the time to read that and then give you a number between 0 and 100.
it not only has this signal index but also an electromyogram there
saying poor signal that's probably just because i'm moving around and it's just trying to get
the reading and that's the provisional reading of 97 which means i'm very awake so really the
levels here are anesthesia is generally between 40 to 60 and most of the time if i'm running
an anesthetic i want the patient between 40 and 60. 60 to 80 is sedated and 80 and above
is generally the patient might be awake now if you want really deep anesthesia this is generally
below 20 to you know 20 to 40 and below 20 is called burst suppression where you've got very
little brain activity because you have so much anaesthetic on board so i think a lot of these
things are really reassuring for example the rate of awareness under general anesthesia is
very very low also the fact that the anaesthetist is with the patient for the entire period that the
surgeons are operating so we're there looking at every single beat of your heart we're right there
to look at any problems and sort them out really quickly and we've got lots of monitors at hand so
we've got your heart rate your blood pressure respiratory we're watching this the whole time
and we've got end tidal volatile concentrations as well as these fancy monitors which are pretty
good at giving you this kind of reading and just an extra level of security as well
so that means that really there's very few circumstances where your rate of
risk of awareness is going to be extremely high so the next question is especially for those
practicing anesthetics and just learning this when is your patient at high risk of having awareness
and the general anesthesia and this nap study in that five went through some of these risk factors
now there's certain drug factors which means having a neuromuscular blocker thiopenternius
and also total intravenous anesthesia obviously with tiva or total intravenous anesthesia you
can't measure that concentration in the blood perfectly accurate accurately therefore there's
a high risk of all the reasons we mentioned before disconnections as well as not being able to really
know exactly what the concentration is in the body neuromuscular blockers obviously because
if the patient's paralyzed you're not going to see those movements happen before the patient is
aware so they highlight some patient factors being female gender age so not children but the lower
adult range as well as obesity previous accidental awareness under general anesthesia as
well as potential difficult airway and potential difficult airway is always a risk because suddenly
because you're trying to manage the airway and manage the oxygenation of the patient then
it's far more likely that you won't be having time to give those anesthetic medications inhaled so
you'll need someone specifically for keeping the patient asleep so if i expect someone to have a
difficult airway i'll want someone just on the anesthetic while i'm doing the airway you really
want to be able to divide those tasks up to make sure that your patient has someone managing their
you know awareness state as well as the human dynamics and someone else managing the potential
problems of a difficult airway there's some particular subspecialties that are higher risk
so obstetrics is high risk cardiothoracics is high risk and any real emergency operation where you
have very fragile patients you'll have to try and limit the amount of anesthetic give them to keep
them safe as well so there's always a high risk in those situations there are also some situational
factors to be completely aware of which means if your patient is having an emergency crisis
that's at high risk of awareness as well out of ours operating and junior and easterners so make
sure in these circumstances you're really watching yourself make sure that you've got someone else
thinking about these things as well so in these circumstances make sure you're thinking about
accidental awareness and doing things to manage that as a problem as well so thanks so much for
watching i hope you enjoyed this video and i hope you gave you some insight into anesthesia
and the risk of being aware under anesthesia and that it's a very low risk and there's a
lot of things that we do to make sure that our patients are safe so if you like this video
please share with anyone who might be interested and see you next time thanks a lot for watching