Neat Machines that decrease mishaps during surgery

[ThinkFast007]

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I know most of us here are real interested in Gas, typically we talk about the 'how to get in to....." or "is my chance of going there.....". But I was wondering if perhaps we could talk about 'new advances' (or ones that have been recently instituted but us third years aren't that acquainted with yet. I figure if we're all passionate about this field, perhaps knowing the 'small' things will make things more interesting and knowledgeable. I'll start.

Recently, I was talking to one of the anesthesiologists here and he was talking about how back in the day NO2 poisoning was such a big thing. For example, someone could be reading a magazine 😀 and accidentally just push the NO2 button and not know it. Nowadays, you can't give a person NO2 by accident (unless the machine is malfxn) because the valve that let's the NO2 out is first opened by the positive pressure created by the O2. I thought it was pretty neat (yah sounds nerdy, but heck if it's going to make life less lawsuit prone and promotes the well being of the pt then it's a great idea!).

Any other neat little things like this?

 

[Skip Intro]

The two main pieces of equipment that changed the field of anesthesia are: (1) the capnograph, and (2) the pulse oximeter. Intra-operative deaths related to anesthesia dropped dramatically with the regular use of these two devices. One attending told me one time that, back in the day, it was more like, "hey, doesn't the patient look a little blue... maybe I should adjust the flows up a little bit" and that was the way you basically ran a case. That, and you got a lot of blood gasses if you weren't sure.

Lately, there has been a big push, especially with all the suspect "news reports" of awareness during anesthesia, into scaring the crap out of the general public that anesthesia is dangerous and scary. Basically, in the lay media, they're telling patients to push anesthesiologists to utilize BIS monitoring to protect them from having sensation during the procedure. (There was a news report on this just last night.)

This (awareness) is still a relatively minor problem that happens very infrequently. The only case I've personally heard of, that was presented at an M&M during a rotation, was of a patient who apparently failed to awaken after her procedure was over. Turns out she was one of the unfortunate few who had an abberant plasma cholinesterase and succinylcholine knocked her out, all totaled, for about 2 hours. The problem was, the gas was off, she was "wide awake" and completely aware but couldn't move or respond. They kept TOF'ing her with the nerve stim, and, in addition to being fully conscious, intubated, and unable to move or respond, that's what she remembered and was terrified because she didn't know what was going on. Has anyone ever stimmed themselves? I TOF'd myself one time (and with the setting only like on 4)... basically, it completely hurts like ****. Anyway, this patient was never in danger and there was no way a BIS could have predicted or protected her from this. It just sucked because it scared the crap out of her. Fortunately, with some good post-op counseling and offer to do cholinesterase testing free of charge (I think there is a registry?), she never threatened to sue.

A lot of attendings I've talked to feel that the BIS is basically useless, and they won't use it even if it's in the room. You know how it goes, until practice groups get reimbursed for providing this extra-level of monitoring, it's not going to be widely used. So, instead the company that makes it uses dubious marketing tactics, namely putting out B-roll to TV stations under the guise that it is a "news story", which really just serves to misinform and scare the crap out of John Q. Public. The ultimate goal is that patients will complain if they are not given this monitor during the procedure, and this will pressure practice groups to invest in this technology if they haven't already. Don't get me wrong, I'm all for BIS. I'm just not that sure how much it changes the outcome or helps to prevent awareness (and, no, I don't mean that I don't understand how bispectral monitoring works - I do). It still seems that Aspect Medical Systems is bent on putting out this information, unfortunately, under questionable motives.

More info: http://anesthesiologyinfo.com/articles/02222004.php & http://www.outpatientsurgery.net/2000/os01/os01f5.html

-Skip

 

[ThinkFast007]

The two main pieces of equipment that changed the field of anesthesia are: (1) the capnograph, and (2) the pulse oximeter. Intra-operative deaths related to anesthesia dropped dramatically with the regular use of these two devices. One attending told me one time that, back in the day, it was more like, "hey, doesn't the patient look a little blue... maybe I should adjust the flows up a little bit" and that was the way you basically ran a case. That, and you got a lot of blood gasses if you weren't sure.

Lately, there has been a big push, especially with all the suspect "news reports" of awareness during anesthesia, into scaring the crap out of the general public that anesthesia is dangerous and scary. Basically, in the lay media, they're telling patients to push anesthesiologists to utilize BIS monitoring to protect them from having sensation during the procedure. (There was a news report on this just last night.)

This (awareness) is still a relatively minor problem that happens very infrequently. The only case I've personally heard of, that was presented at an M&M during a rotation, was of a patient who apparently failed to awaken after her procedure was over. Turns out she was one of the unfortunate few who had an abberant plasma cholinesterase and succinylcholine knocked her out, all totaled, for about 2 hours. The problem was, the gas was off, she was "wide awake" and completely aware but couldn't move or respond. They kept TOF'ing her with the nerve stim, and, in addition to being fully conscious, intubated, and unable to move or respond, that's what she remembered and was terrified because she didn't know what was going on. Has anyone ever stimmed themselves? I TOF'd myself one time (and with the setting only like on 4)... basically, it completely hurts like ****. Anyway, this patient was never in danger and there was no way a BIS could have predicted or protected her from this. It just sucked because it scared the crap out of her. Fortunately, with some good post-op counseling and offer to do cholinesterase testing free of charge (I think there is a registry?), she never threatened to sue.

A lot of attendings I've talked to feel that the BIS is basically useless, and they won't use it even if it's in the room. You know how it goes, until practice groups get reimbursed for providing this extra-level of monitoring, it's not going to be widely used. So, instead the company that makes it uses dubious marketing tactics, namely putting out B-roll to TV stations under the guise that it is a "news story", which really just serves to misinform and scare the crap out of John Q. Public. The ultimate goal is that patients will complain if they are not given this monitor during the procedure, and this will pressure practice groups to invest in this technology if they haven't already. Don't get me wrong, I'm all for BIS. I'm just not that sure how much it changes the outcome or helps to prevent awareness (and, no, I don't mean that I don't understand how bispectral monitoring works - I do). It still seems that Aspect Medical Systems is bent on putting out this information, unfortunately, under questionable motives.

More info: http://anesthesiologyinfo.com/articles/02222004.php

-Skip

the obvious q from a third year med student....What's BIS ? Or atleast what does it stand for so I can look it up.

Thanks

 

[Skip Intro]

the obvious q from a third year med student....What's BIS ? Or atleast what does it stand for so I can look it up.

Thanks

Just google "BIS monitoring".

-SKip

 

[seattledoc]

Why wouldn't the BIS have helped her? It would have read in the 90-plus range (awake) and everyone in the room would have said, hmmm, wide awake on the BIS yet not breathing/moving/no twitches. The BIS probably would have prompted somebody to sedate her until things were resolved.

Anyway, this patient was never in danger and there was no way a BIS could have predicted or protected her from this. It just sucked because it scared the crap out of her.

 

[UTSouthwestern]

Why wouldn't the BIS have helped her? It would have read in the 90-plus range (awake) and everyone in the room would have said, hmmm, wide awake on the BIS yet not breathing/moving/no twitches. The BIS probably would have prompted somebody to sedate her until things were resolved.

Anyway, this patient was never in danger and there was no way a BIS could have predicted or protected her from this. It just sucked because it scared the crap out of her.

Not necessarily. We have evaluated the BIS extensively at Zale and Baylor Dallas and have still found that the correlation of the raw score does not always correlate to the depth of anesthesia that it should.

Baxter's PSA 4000 even without the upcoming independent bi-hemispheric electrodes, has proven to us to be a more effective monitor and will likely supplant the BIS before BIS even has had the opportunity to corner the market.

I, personally prefer the PSA 4000's raw 4 lead EEG data along with its ability graph out all of the readings obtained during the case and the PSA 4000 is currently the SOC for CPB cases at Baylor Dallas. With a numerical value that may be borderline for adequate anesthetic depth (50 for the PSA 4000), you can evaluate the raw EEG to evaluate the presence or absence of delta waves, etc. and guide your therapy subsequently.

Too great of an anesthetic depth is also more easily assessed with the 4000 and a cumulative score of less than 25 or flat EEG for too long a period of time can be easily assessed with the PSA 4000.

Just my 2 cents worth.

 

[Skip Intro]

Why wouldn't the BIS have helped her? It would have read in the 90-plus range (awake) and everyone in the room would have said, hmmm, wide awake on the BIS yet not breathing/moving/no twitches. The BIS probably would have prompted somebody to sedate her until things were resolved.

Because they had turned off the gas and were emerging her anyway. She should have been waking up. That's the point. At that point they knew she should be awake, they just couldn't figure out why she wasn't moving. Barring the obvious "something's wrong here" that the anesthesiologist should have picked up on, BIS wouldn't have added anything to this except, as you point out, that the numbers probably would have been in the consciousness range. At least he did the right thing by calling other colleagues in to troubleshoot.

Their conclusion was that BIS (and it was discussed) just wouldn't have added anything to this case. They should have known better than to keep hitting her with the nerve stimulator. That was the point of why this was presented at the M&M.

-Skip

 

[seattledoc]

I agree that it isn't a perfect tool but I would also say that it does a good job of assessing "awake". I've not done extensive studies on the BIS but I have found it to consistently be in the "awake range" when the patient is able to open their eyes! In other words, this patient would not have had a BIS in the 30-40 range reassuring everyone in the room that she was not aware of the events, rather it would have been higher and hopefully would have promped somebody to consider sedation. Stick one on yourself and see what it says. If anybody gets a BIS value consistently below 75, let us know and then cut back on your xanax 😀

Not necessarily. We have evaluated the BIS extensively at Zale and Baylor Dallas and have still found that the correlation of the raw score does not always correlate to the depth of anesthesia that it should.

 

[seattledoc]

yeah, I agree that this situation could have been dealt with better with or without the BIS. The BIS was not in any way critical to avoiding the 2 hours of awareness but it would have helped.

Because they had turned off the gas and were emerging her anyway. She should have been waking up. That's the point. At that point they knew she should be awake, they just couldn't figure out why she wasn't moving. Barring the obvious "something's wrong here" that the anesthesiologist should have picked up on, BIS wouldn't have added anything to this except, as you point out, that the numbers probably would have been in the consciousness range. At least he did the right thing by calling other colleagues in to troubleshoot.

Their conclusion was that BIS (and it was discussed) just wouldn't have added anything to this case. They should have known better than to keep hitting her with the nerve stimulator. That was the point of why this was presented at the M&M.

-Skip

 

[Skip Intro]

yeah, I agree that this situation could have been dealt with better with or without the BIS. The BIS was not in any way critical to avoiding the 2 hours of awareness but it would have helped.

Again, don't get me wrong. I think there's a role for BIS monitoring, especially in spinal cases or any other situation where you have to balance keeping the patient light vs. adequately sedated. But, from what I've read on the subject and what's been impressed on me thus far, the jury seems to be out as to the necessity of it's utilization in every case. Even then, it's not going to prevent awareness 100% of the time, like people (I believe) are being now mistakenly lead to believe in TV news reports like the one I saw last night.

-Skip

 

[seattledoc]

Yeah, we reviewed a paper in journal club and one of the things that was discussed was that there are certain situations where a majority of awareness occurs (trauma, cards, and obstetrics). In these situations the BIS may be more useful than if it is used in every case in the OR. The number needed to treat and the cost per prevented episode go up considerably when the BIS is used in all cases.

Again, don't get me wrong. I think there's a role for BIS monitoring, especially in spinal cases or any other situation where you have to balance keeping the patient light vs. adequately sedated. But, from what I've read on the subject and what's been impressed on me thus far, the jury seems to be out as to the necessity of it's utilization in every case. Even then, it's not going to prevent awareness 100% of the time, like people (I believe) are being now mistakenly lead to believe in TV news reports like the one I saw last night.

-Skip

 

[jem04]

Why wouldn't the BIS have helped her? It would have read in the 90-plus range (awake) and everyone in the room would have said, hmmm, wide awake on the BIS yet not breathing/moving/no twitches. The BIS probably would have prompted somebody to sedate her until things were resolved.


Don't be so sure--- the BIS reading may have still been down due to the neuromuscular blockade from the sux (see the following study (who were these volunteers?)). I agree that the BIS may be interesting (and fun) to use sometimes (like when it says 00 during circ arrest cases) but I certainly don't think it is an ideal awareness monitor.

The bispectral index declines during neuromuscular block in fully awake persons.

Messner M, Beese U, Romstock J, Dinkel M, Tschaikowsky K.

Department of Anesthesiology, Friedrich-Alexander Universitat, Erlangen-Nuernberg, Germany. [email protected]

Bispectral index (BIS) is an electroencephalographic variable promoted for measuring depth of anesthesia. Electromyographic activity influences surface electroencephalography and the calculation of BIS. In this study, we sought to determine the effect of spontaneous electromyographic activity on BIS. BIS was monitored in three volunteers by using an Aspect A-1000 monitor. The experiment was repeated in one volunteer. Electromyographic activity was recorded. Alcuronium and succinylcholine were administered. No other drugs were used. In parallel with spontaneous electromyographic activity of the facial muscles, BIS decreased in response to muscle relaxation to a minimum value of 33 and, in the repeated measurement, to a minimum value of 9 when total neuromuscular block was achieved. In two volunteers, no total block was achieved. BIS decreased to a minimal value of 64 and 57, respectively. In turn, recovery of BIS coincided with the reappearance of spontaneous electromyographic activity. During the entire experiment, the volunteers had full consciousness. BIS, assessed by software Version 3.31, correlates with spontaneous electromyographic activity of the facial muscles. BIS failed to detect awareness in completely paralyzed subjects. Thus, in paralyzed patients, BIS monitoring may not reliably indicate a decline in sedation and imminent awareness. IMPLICATIONS: The bispectral index (BIS) is an electroencephalographic variable intended for measuring depth of anesthesia. Electromyographic activity influences the calculation of BIS. We found that the administration of a muscle relaxant to unanesthetized volunteers decreases the bispectral index value. Thus, awareness in totally paralyzed patients cannot be excluded.

 

[Pinky]

Don't be so sure--- the BIS reading may have still been down due to the neuromuscular blockade from the sux (see the following study (who were these volunteers?)).

my attending was telling me about this study or about a similar one where the volunteers were medical students.

 

[seattledoc]

wow, I wish I had this article for our journal club. I stand corrected, maybe the BIS wouldn't have done any good. And yes, these volunteers were nuts to volunteer for this study.

[email protected][/email]

Bispectral index (BIS) is an electroencephalographic variable promoted for measuring depth of anesthesia. Electromyographic activity influences surface electroencephalography and the calculation of BIS. In this study, we sought to determine the effect of spontaneous electromyographic activity on BIS. BIS was monitored in three volunteers by using an Aspect A-1000 monitor. The experiment was repeated in one volunteer. Electromyographic activity was recorded. Alcuronium and succinylcholine were administered. No other drugs were used. In parallel with spontaneous electromyographic activity of the facial muscles, BIS decreased in response to muscle relaxation to a minimum value of 33 and, in the repeated measurement, to a minimum value of 9 when total neuromuscular block was achieved. In two volunteers, no total block was achieved. BIS decreased to a minimal value of 64 and 57, respectively. In turn, recovery of BIS coincided with the reappearance of spontaneous electromyographic activity. During the entire experiment, the volunteers had full consciousness. BIS, assessed by software Version 3.31, correlates with spontaneous electromyographic activity of the facial muscles. BIS failed to detect awareness in completely paralyzed subjects. Thus, in paralyzed patients, BIS monitoring may not reliably indicate a decline in sedation and imminent awareness. IMPLICATIONS: The bispectral index (BIS) is an electroencephalographic variable intended for measuring depth of anesthesia. Electromyographic activity influences the calculation of BIS. We found that the administration of a muscle relaxant to unanesthetized volunteers decreases the bispectral index value. Thus, awareness in totally paralyzed patients cannot be excluded.

 

[Skip Intro]

Good find, jem04! Interesting study. And, at the very least, this again proves beyond a shadow of a doubt that medial students will do just about anything to impress their attendings.

-Skip

 

[UTSouthwestern]

Good find, jem04! Interesting study. And, at the very least, this again proves beyond a shadow of a doubt that medial students will do just about anything to impress their attendings.

-Skip

Why are we not suprised. Yikes. To emphasize the point, the BIS is not the end all for AUA monitoring and may in fact distract you from using your clinical judgement to address the situation. For example, your patient is tearing profusely and is 90% paralyzed, but the BIS says 40, so you abstain from increasing the anesthetic depth.

 

[Skip Intro]

Why are we not suprised. Yikes. To emphasize the point, the BIS is not the end all for AUA monitoring and may in fact distract you from using your clinical judgement to address the situation. For example, your patient is tearing profusely and is 90% paralyzed, but the BIS says 40, so you abstain from increasing the anesthetic depth.

This is a criticism I vaguely remember hearing one time as well, i.e. that the BIS may not really be monitoring what it is puported to be monitoring, namely brain activity, and may in fact be acting more like an EMG. I just can't now recall where I heard this or who said it to me. Again, in a case where you're not paralyzing (like a spinal case), BIS may be a good overall tool to monitor relaxation and, hence, depth of anesthesia. Whether it truly does always highly correlate with brain activity....

In one of the articles I linked above, two anesthesiologists have a point/counterpoint discussion about the pros and cons of BIS that is worth the read. One of the things they talk about is this very phenemenon you allude to, UTSouthwestern. It's true that this tool may ultimately prove to be just be an extra gadget that distracts the anesthetist away from focusing on using clinical acumen and experience to evaluate the patient, but it's still too soon to tell. Regardless, none of us should ever forget the golden rule of patient evaluation we've all been taught early on as clinicians: monitor the patient, not the monitor (which you should never 100% trust anyway).

-Skip

 

[UTSouthwestern]

This is a criticism I vaguely remember hearing one time as well, i.e. that the BIS may not really be monitoring what it is puported to be monitoring, namely brain activity, and may in fact be acting more like an EMG. I just can't now recall where I heard this or who said it to me. Again, in a case where you're not paralyzing (like a spinal case), BIS may be a good overall tool to monitor relaxation and, hence, depth of anesthesia. Whether it truly does always highly correlate with brain activity....

In one of the articles I linked above, two anesthesiologists have a point/counterpoint discussion about the pros and cons of BIS that is worth the read. One of the things they talk about is this very phenemenon you allude to, UTSouthwestern. It's true that this tool may ultimately prove to be just be an extra gadget that distracts the anesthetist away from focusing on using clinical acumen and experience to evaluate the patient, but it's still too soon to tell. Regardless, none of us should ever forget the golden rule of patient evaluation we've all been taught early on as clinicians: monitor the patient, not the monitor (which you should never 100% trust anyway).

-Skip

I like that quote: "Monitor the patient not the monitor". Sums it all up. I do think there is a place for AUA monitors, but after extensive use of EEG, PSA 4000, and BIS, I find the BIS to be of the LEAST utility likely from its oversimplification of its data presentation. EEG is likely overkill. At some point, I will likely become a spokesman for the PSA 4000 because of two interesting cases:

In these cases, the patients were undergoing complicated AVR's and multivessel CABG on pump with exceedingly poor functional status (dilated CM, EF<20%, severe bilateral carotid disease, preop IABP on 1:1 augmentation). Our technique was going to have to be narcotic based (fentanyl/remifentanil) with minimal cardiosuppressive agent use. Upon rewarming, we used Precedex infusions at 0.3 to 0.5 mcg/kg/hr for post pump sedation with a minimal amount of isoflurane (.2-.4%) for as much amnesia as could be provided. Both patients required high doses of epi (up to 0.2 mcg/kg/min) and/or Primacor to come off pump, with pacing to maintain adequate perfusion and continued IABP use. Watching the PSA 4000, I noted 5 instances where the raw EEG showed evidence of the patients being awake and the cumulative score also indicated an inadequately sedated patient. We had discussed this possibility with both patients in detail preoperatively and during these events, I wanted to see if the patients could recall what I said to them. So for each instance, I said something that was distinctive ("I want you to relax and imagine that you are on a beach at Hawaii", "I want you listen to the sound of the monitor and know that it is your heart that is making that strong sound", etc.)

By post op day 2, both patients were extubated and I spoke extensively with them and both recalled what I said in suprising detail and did not recall other statements I made when the PSA clearly showed that anesthetic depth was more than adequate. Both were also very satisfied with the anesthetic provided, which I would like to attribute to preoperative education and counseling as well as the Precedex.

 

[Skip Intro]

... both recalled what I said in suprising detail and did not recall other statements I made when the PSA clearly showed that anesthetic depth was more than adequate.

Wow! That is really fascinating. You should think of a way that this could be further studied / written-up (if you haven't already... 😉 ).

-Skip

 

[UTSouthwestern]

Wow! That is really fascinating. You should think of a way that this could be further studied / written-up (if you haven't already... 😉 ).

-Skip

Case reports upcoming later (probably end of the year). Kinda burned out right now. We are in the middle of a couple of extensive studies on the PSA 4000.