When Anesthesia Fails...

[House of Gas]

Did anyone catch this program on the Discovery Health channel? It was about anesthesia awareness, or patients "waking up" during a surgery. The program really presented this as a somewhat common occurance that caused it's "victims" irreparable psycological damage. One case involved a woman becoming aware during a c-section, another during a hernia repair, and another during an enucleation procedure. At the end, the program hailed the advent of the BIS monitor as the solution to this problem. Comments??

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[NaeBlis]

I heard all the recent research and intrest into anesthesia awareness has been supported by the makers of the BIS monitor. Seems like self promotion more than anything else, and of course the media loves stuff like this.

 

[Tenesma]

all the most recent studies regarding depth of anesthesia as far as awareness and mortality rates have been sponsored by Aspect Medical (the manufacturer of the BIS monitor)... so the news they are putting out there (which the media loves because it is scary and increases ratings) is a bit over embellished.

1) awareness is very infrequent in the general population - the numbers that they used include Trauma and Obstetric numbers (which are always going to make the numbers look falsely elevated)

2) BIS only uses 2 different brainwaves: 3 and 4 Hz - it doesn't take into account blood pressure, heart rate or anything else - the newer BIS has a software algorithm to try to eliminate electro-cautery interference. And has only been shown to be effective in the setting of propofol/barbiturates/volatile anesthetics... A BIS is useless if you are doing a nitrous narcotic technique, or if you are using ketamine.

3) in fact some of the reticular activating formation that is responsible for a large part of the waves that is picked up, can send some false information.... for example, if somebody is paralyzed and therefore there is diminshed afferent input to the reticular activating formation then you will have a lower BIS.

4) i have used the BIS a lot - and there have been times where the number reads 40 (which according to the literature suggests unconsciousness) and the patien is talking to me - or vice-versa a number of 98 and the patient doesn't arouse for 15 minutes.

I think there are certain situations where the BIS may be helpful: ie, a AAA with epidural running, full paralysis and just a touch of volatile - that way you may feel a bit more comfortable running very low volatile to fuzz their memory.

It is not a bad tool - but it is not the hoped-for depth-of-anesthesia-monitor that we all pray for every day.... in fact, these TV specials are giving the patients too much information: a few weeks ago during a pre-op for a crani a patient was very distressed that we wouldn't be using a BIS monitor - 1) it was a nitrous narcotic technique 2) the sensing pads would be in the surgeons field.... and you know how patients believe everything they see on TV

 

[thegasman]

I thought some of the characters on the show were a little sketchy. One guy had open heart surgery in like 1960, and then after "having his heart shocked" a few years ago all of a sudden he remembered his heart surgery after previously having no awareness. I think this was the same guy who later on said that he was so traumatized that he could no longer work!!?? That sounds like some kind of bogus disability claim to me. But maybe I am a little jaded.

I also think that for the patient who underwent an emergency c-section and some awareness, this awareness might be a consequence of the emergent situation.

I do believe that it would be traumatic to wake up during surgery, but I think this show misrepresented the events a little bit to be dramatic for tv. This is not an everyday occurrence by any means.

 

[UTSouthwestern]

My opinion of the BIS is that it is too variable with respect to depth of anesthesia from patient to patient and we as practitioners will become too focused on its numbers and not on what a previous poster noted: clinically observable parameters.

All in all, the BIS will serve to lower our diligence as we become comforted by looking at a number that says "great anesthetic dude."

 

[gaslady]

I have seen so many cases where the BIS monitor didn't correlate with the patient's state or where it just didn't work. It seems like the cables aren't very sturdy and frequently break giving erroneous readings.

There's an anesthesia awareness website www.anesthesiaawareness.com
This website shows a dramatized view of the problem that's probably similar to the TV program referred to above. One noteworthy thing about the site is how many times it asks for donations throughout.

The fact is that awareness under anesthesia is a risk. The risk is small for routine cases. However, for trauma, OB, and even cardiac cases the risk increases and for good reason. In trauma many of the drugs given for anesthesia have significant hemodynamic consequences, When your patient is bleeding to death are you more worried about keeping them alive or keeping them from possibly remembering things. Ideally you want to do both, but sometimes the goals are at odds with each other. For OB, the time course of the anesthetic is done differently in order to reduce the amount of sedatives that the baby receives. Again there's conflicting sides. In most cases it works out fine, but which would you rather have happen: the baby needing to be resuscitated or the mother remembering the sensation of the ET tube or hearing the surgeons/nurses talking for part of the delivery?

Part of the problem is that there is no foolproof way to measure "depth of anesthesia". In fact it's so difficult to determine that the term is really a misnomer. Depth of anesthesia is used frequently, but it is more appropriate to instead discuss the specific components of anesthesia: unconsciousness, amnesia, analgesia, paralysis
Another point is that due to personal variation in metabolism of the various drugs, a patient can be dosed accordingly and still be lacking in one of the components of anesthesia.