Awareness under General Anesthesia

[coffeebythelake]

The lit says that when no particular risk factors are present the risk of awareness is 1 to 2 cases per 1000 anesthetizations (0.1% to 0.2%)
So it's likely in a career you will encounter this issue multiple times

1. What's your practice for patients you deem high risk for awareness under GA?

- Ply them with a ton of benzos?
- Keep them well above 0.7 MAC?
- Use BIS? Controversial that this actually decreases the risk.
- Avoid muscle relaxants? Many cases this is not possible

2. What is your end point if you decide to up the anesthetic dose?

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[coffeebythelake]

As a related comment, I recently anesthetized a "severely anxious and claustrophobic" obese 50-60 year old patient for a 45 minute MRI. Got 6 mg versed, 5 mg haloperidol, 50 mg IV benadryl, didn't give any propofol because of airway concerns. He took a short nap but was otherwise completely awake and had almost full recall of the experience. He has never had GA before, but i imagine this guy would probably be one of these high risk for awareness cases under GA.

 

[deleted59964]

High risk for awareness -

yes I'd give some benzo unless there is a good reason not to.
I'd avoid TIVA and keep MAC close to 1
I would use BIS - but only for medico-legal reasons.
Yes if possible I wouldn't paralyse

A lot of awareness is at induction - particularly in the setting of prolonged airway management, if possible I'd have a second person keep giving propofol as appropriate if laryngoscopy was taking a while.

A lot of complaints of awareness in NAP5 where at emergence too - where patients recalled having residual neuromuscular blockade on awakening, they interpret that as accidental awareness. So I'd use neuromonitoring and reverse as indicated.

don't think there's much else you can do, except introduce yourself to the patient using one of your less liked colleagues names

 

[dhb]

I run patients pretty light, have done probably 20k cases and have not had a complain of recall yet...
I'm willing to bet a lot of the awarenesses from the litterature are regional cases with sedation.

 

[woopedazz]

I've only ever had one patient swear up and down that they were "aware" during the anaesthetic; BIS of 35-45 throughout running TIVA. However, I don't think it was a true recollection as they took forever to wake up post-reversal and couldn't recall a single accurate event between "breathe through this mask" and waking up in recovery. I think the mind plays tricks on people sometimes, but who knows, maybe I'm wrong and they did have some recollection; it just wasn't perfectly accurate.

As an aside: Nurses where I am flag heaps of patients who have experienced "awareness" during scope lists. Make a huge song and dance about how this patient suffered an extremely rare complication of anaesthesia... blah blah blah... Patient feels very special after the 10th time they are told how special and unfortunate they are. Start believing it even more strongly... suddenly everyone believes they actually had awareness. I hate it.

 

[deleted59964]

I run patients pretty light, have done probably 20k cases and have not had a complain of recall yet...
I'm willing to bet a lot of the awarenesses from the litterature are regional cases with sedation.

and just straight up sedation - for scopes etc.. which I view as a failure of communication

 

[deleted59964]

As an aside: Nurses where I am flag heaps of patients who have experienced "awareness" during scope lists. Make a huge song and dance about how this patient suffered an extremely rare complication of anaesthesia... blah blah blah... Patient feels very special after the 10th time they are told how special and unfortunate they are. Start believing it even more strongly... suddenly everyone believes they actually had awareness. I hate it.

I believe in Europe some places don't give sedation for colonoscopies.

 

[Aether2000]

Double scopolamine patches.

 

[Mman]

The lit says that when no particular risk factors are present the risk of awareness is 1 to 2 cases per 1000 anesthetizations (0.1% to 0.2%)
So it's likely in a career you will encounter this issue multiple times

1. What's your practice for patients you deem high risk for awareness under GA?

- Ply them with a ton of benzos?
- Keep them well above 0.7 MAC?
- Use BIS? Controversial that this actually decreases the risk.
- Avoid muscle relaxants? Many cases this is not possible

2. What is your end point if you decide to up the anesthetic dose?

Patients that are at "high risk" for awareness are almost always too unstable to run deep. That's why they are high risk. I try to get some benzos and maybe ketamine in their system.

I also do not believe the risk of awareness under GA in your average patient is 1/1000. I think that might be at least an order of magnitude off. We do about 100,000 cases a year (not all GA obviously), but it is pretty darn rare that we have someone with awareness. Do we not hear about some of them? I'm sure, but it still can't be THAT common. I've met a small handful of people in the last 10 years that have either probably or definitely had awareness. Half of those patients weren't even concerned about it because they knew they were dying and were grateful to have lived through it.

The overwhelming majority of patients that tell me about their previous awareness under anesthesia were having a procedure under sedation combined with either a nerve block or a spinal or something similar.

 

[DM27]

I agree with the above post about the likely overstated incidence of true awareness. I do not personally change my anesthetic plan for general due to independent awareness concerns without established risk factors. With the exception of adding a BIS monitor (for what it's worth) to the truly higher risk groups such as cardiac cases and people who are either high level alcoholics or on chronic large doses of psychoactive meds (benzos, antipsychotics, opioids) where their MAC and pharmacologic responses may not fall into predictable population averages. If a BIS monitor was not available, it wouldn't really give me much pause either.

For non-general cases I usually tell people that they'll be "asleep" (if it's what they want) but they will likely have vague memories of coming into the room and leaving the room and if there is music playing or recurring loud sounds it wouldn't be surprising if they woke up with some memory of it, but that they should be comfortable throughout the procedure.

 

[OTCAwesome]

For patients who are actively dying and will in no way tolerate even a whiff of volatile, versed and paralytic +/- ketamine

Severe hypotension is also one hell of an amnestic.

 

[coffeebythelake]

I believe in Europe some places don't give sedation for colonoscopies.

I've seen anesthesiologists label these MAC endoscopy cases as IVGA. Wonder if this is messing up the stats

 

[coffeebythelake]

For patients who are actively dying and will in no way tolerate even a whiff of volatile, versed and paralytic +/- ketamine

Severe hypotension is also one hell of an amnestic.

Yes, unstable patients, awareness is low on my list. They should count their lucky stars to be alive. I do like to give them a large dose of verses though

 

[dhb]

I run patients pretty light, have done probably 20k cases and have not had a complain of recall yet...
I'm willing to bet a lot of the awarenesses from the litterature are regional cases with sedation.

Actually i did have a case: sternotomy under sux for ruptured pulm artery 😆

 

[dhb]

Even when patients wake up in the middle of a coloscopy under strait propofol they don't recall it.
Otoh i know of a guy who forgot to turn the sevo dial and the patient repeated verbatim what had been said in the OR.

 

[deleted59964]

Ceaserians under GA are the high risk group i worry most about.

agree unstable / trauma patients that don’t tolerate much anaesthetic are high risk - but yeah prevention of awareness most sometimes take a back seat to CVS stability

 

[Mman]

Even when patients wake up in the middle of a coloscopy under strait propofol they don't recall it.
Otoh i know of a guy who forgot to turn the sevo dial and the patient repeated verbatim what had been said in the OR.

I've seen trauma patients that got Rocuronium in the ED and weren't given any sedatives for hours that eventually came to the OR that had some pretty good recall of events through the ED and radiology and entering the OR.

 

[shepardsun]

Slightly off topic, but does anybody use raw EEG monitoring for trending depth of anesthesia? We don't have BIS at our shop, but we do have the Sedline, and while the proprietary numbers they spit out are pretty worthless, looking at the density spectral array or the raw EEG has helped me feel more comfortable with that sick little old lady getting 20 mcg/kg/min of propofol and still being intermittently burst surpressed.

 

[Hork Bajir]

I routinely use sedline for TIVA cases. Definitely helpful for monitoring depth of anesthesia, both in terms of preventing awareness but also for timing wake up (oftentimes I've been able to cut my propofol dose lower than I otherwise would have guessed, leading to faster emergence at the end). I would caution you though, that it is definitely not a perfect monitor. The Sedline does NOT give you "raw" EEG"- it gives you a processed, compressed modified frontal EEG. Still useful, but the processing software is a bit of a black box.

We had a case of awareness recently (the bad kind- aware, in pain, afraid, with explicit recall) where the spectral array on the sedline looked for all the world like a patient under general anesthesia. A member of our department who does his research on EEG later took the data from that case back to his lab and got rid of the post-processing that the Sedline does (converting it back to a true raw EEG), at which point it became pretty clear that there was higher frequency low amplitude activity. This obviously would have been concerning had it been seen at the time. In this particular case, the pitfall was that the patient was elderly and had mild hepatic encephalopathy, both of which can decrease the amplitude of the higher frequency signals; the sedline presumably has a high-pass filter, among other things, because those ultra-low amplitude wavelengths were filtered out of the spectral array.

If you're using a Sedline and you're really worried about awareness for whatever reason, I suggest putting the Sedline on pre-induction and make it a point to get a good baseline reading. This involves taking an extra 30 seconds where no one is touching the patient, and you instruct them to lay still as possible with their eyes closed. Not something you necessarily wanna do for every case given it's a minor PITA, but on more than one occasion I've been surprised by how "anesthetized" a patient's awake EEG looks, and this has stopped me from using the EEG to be falsely reassured during the case.

 

[jwk]

I also do not believe the risk of awareness under GA in your average patient is 1/1000. I think that might be at least an order of magnitude off. We do about 100,000 cases a year (not all GA obviously), but it is pretty darn rare that we have someone with awareness. Do we not hear about some of them?

Thanks to our old Emory friend for that lovely 1/1000 study quite a few years back. It was suggested in a Letter to the Editor one of the journals or the ASA Newsletter that if this anesthesiologist's incidence of awareness was truly that high that he might want to consider a better anesthetic technique.

 

[drmwvr]

I don't care about awareness...I care about recall...

 

[MirrorTodd]

Even when patients wake up in the middle of a coloscopy under strait propofol they don't recall it.
Otoh i know of a guy who forgot to turn the sevo dial and the patient repeated verbatim what had been said in the OR.

JFC