Bispectral index (BIS)

[shr7]

I know there are several surgeons and surgical PA's on this board, I am wondering if there are any ICU docs as well? Down at the local hospital we use the BIS frequently in cases where general anesthesia is used. I have no personal experience with the OR, but I was wondering how widespread the practice of using this monitoring parameter is. It seems the BIS is only indicated for monitoring the hypnotic effects of general anesthetics and sedatives. Recently, though, it seems it was approved as a parameter to control awareness incidence. With this new indication, the BIS seems to have proliferated in differing environments.

My question is to any ICU docs out there. Do you use the BIS to control ICU sedation? As a stupid young pharmacy student talking in front of a bunch of stupid young med students, I would hate to sound like a total jackass. My literature search revealed mixed results, with some passionate articles written both for, and against, its use. It seems the advantage is to use it to monitor for deep sedation, where monitoring subjectively becomes impossible, as well as monitoring for sedation in ICU patients undergoing NMB. It would seem to be difficult to use in lightly sedated patients because of muscle based electrical activity as well as no differentiation between alert/awake/cooperative and pulling-out-lines/agitated. Would you characterize this position as accurate and/or consistent with your hospital policy?

I am also interested to hear what the surgeons/PA's say who have used or seen this device. As well, I know there are a growing number in use in ambulances and other mobile ICU's. Have any of you paramedics or EMT's seen or used these devices, and to what end?

Thank you very much. I am much more comfortable with drugs than devices. God help me if they ask me how exactly an EEG is translated into a number...

SR

[Ambush Master]

Be advised. There are several Trauma Surgeons (I believe that it is Safe to say that they are familiar with ICUs!!) on this site, plus numerous 18Ds and PAs.

I'm sure that someone will be along shortly.

Martin

[Team Sergeant]

Be advised. There are several Trauma Surgeons (I believe that it is Safe to say thay they are familiar with ICUs!!) on this site, plus numerous 18Ds and PAs.

I'm sure that someone will be along shortly.

Martin

We also have a "Surgical" ICU (SICU) Director I know personally:D

I'll point her to this post......

Team Sergeant

[Doczilla]

I've never used it nor seen it used in our ICUs or EDs here. Didn't see it used in the ICUs back in Tidewater either. I've never heard of it being used by an EMS agency in this or any other area. Doc T or Swatsurgeon can probably speak more authoritatively from the Trauma ICU standpoint and what they might be doing in other areas.

Sedation in our ICUs and ED is titrated based on a sedation scale (modified Ramsay score), which measures such things as arousability, spontaneous movement, communication, etc. It does not work/apply to patients on paralytic drugs because they cannot move or respond, and could in fact be wide awake and terrified under the neuromuscular blockade.

'zilla

[shr7]

Thank you for the input. That seems to be a common theme running across the people I've spoken to. It certainly is a far cry from the company's website where attractive physicians are using it on all of their clean patients in well-lit hospital rooms. It seems that the device spits out a number that is generally accurate, but no one is quite sure what that number means in an ICU setting.

SR

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[Doc T]

I have minimal personal experience with the BIS monitor having only used it twice.... both times patients were on extremely high ventilatory support and were being kept paralyzed so they didn't fight the machine. This is probably the only application I see it as helpful...when patients are paralyzed to make certain you are keeping them appropriately sedated.

The BIS monitor is easy to use but like everything else it is just one piece of the puzzle. You put a sensor on the patient's head and it records brain activity and gives you a number..... a high number (100) means the patient is wide awake.... the lower the number the more sedated... under 60 or so is typically unconscious... you titrate drugs to achieve the level of sedation you want.

In the ICU we typically still use vital signs and such to determine levels of sedation....not the most scientific method and probably we oversedate more than undersedate to be honest.

The OR is a separate entity where it is used regularly. I still don't believe its caught on in the ICUs.....

[Team Sergeant]

shr7,

Doc T is an attending Trauma Surgeon and the Director of an SICU. (She's also my wife.;))

Team Sergeant

[shr7]

Thank you TS for directing Doc T to the post, and thank you Doc T for taking the time to answer my questions. It is absolutely wonderful to be a member of this board and to have access to the caliber of people that wouldn't have time for me in person.

Again, thank you for the response.

[swatsurgeon]

article in this weeks New England Journal of Medicine.... FYI


Anesthesia Awareness and the Bispectral Index

Michael S. Avidan, M.B., B.Ch., Lini Zhang, M.D., Beth A. Burnside, B.A., Kevin J. Finkel, M.D., Adam C. Searleman, B.S., Jacqueline A. Selvidge, B.S., Leif Saager, M.D., Michelle S. Turner, B.S., Srikar Rao, B.A., Michael Bottros, M.D., Charles Hantler, M.D., Eric Jacobsohn, M.B., Ch.B., and Alex S. Evers, M.D.



ABSTRACT

Background Awareness during anesthesia is a serious complication with potential long-term psychological consequences. Use of the bispectral index (BIS), developed from a processed electroencephalogram, has been reported to decrease the incidence of anesthesia awareness when the BIS value is maintained below 60. In this trial, we sought to determine whether a BIS-based protocol is better than a protocol based on a measurement of end-tidal anesthetic gas (ETAG) for decreasing anesthesia awareness in patients at high risk for this complication.

Methods We randomly assigned 2000 patients to BIS-guided anesthesia (target BIS range, 40 to 60) or ETAG-guided anesthesia (target ETAG range, 0.7 to 1.3 minimum alveolar concentration [MAC]). Postoperatively, patients were assessed for anesthesia awareness at three intervals (0 to 24 hours, 24 to 72 hours, and 30 days after extubation).

Results We assessed 967 and 974 patients from the BIS and ETAG groups, respectively. Two cases of definite anesthesia awareness occurred in each group (absolute difference, 0%; 95% confidence interval [CI], –0.56 to 0.57%). The BIS value was greater than 60 in one case of definite anesthesia awareness, and the ETAG concentrations were less than 0.7 MAC in three cases. For all patients, the mean (±SD) time-averaged ETAG concentration was 0.81±0.25 MAC in the BIS group and 0.82±0.23 MAC in the ETAG group (P=0.10; 95% CI for the difference between the BIS and ETAG groups, –0.04 to 0.01 MAC).

Conclusions We did not reproduce the results of previous studies that reported a lower incidence of anesthesia awareness with BIS monitoring, and the use of the BIS protocol was not associated with reduced administration of volatile anesthetic gases. Anesthesia awareness occurred even when BIS values and ETAG concentrations were within the target ranges. Our findings do not support routine BIS monitoring as part of standard practice. (ClinicalTrials.gov number, NCT00281489 [ClinicalTrials.gov] .)

[Doczilla]

A summary on the above quoted study from ACEP News.

Study suggests BIS monitoring may be no better than older technology in preventing anesthesia awareness.
The AP (3/13, Johnson) reports that bispectral index (BIS) monitoring, which is used to "prevent anesthesia awareness," may be "no better than older technology," according to a study published in the March 13 issue of the New England Journal of Medicine. For the study, lead researcher Dr. Michael Avidan, division chief of cardiothoracic anesthesia and cardiothoracic intensive care at Washington University School of Medicine in St. Louis, and colleagues "compared two groups of about 1,000 patients each, all deemed at high risk of waking up during surgery because of health conditions, medication or other factors."
One group was "assigned to BIS-guided anesthesia," while the other group was assigned to receive "conventional anesthesia," according to HealthDay (3/12, Gardner). The researchers found that "[t]wo patients experienced definite anesthesia awareness in each group." Furthermore, "[f]ive...patients (four in the BIS group and one in the control group) had possible awareness."
The researchers said, "Reliance on bispectral index system technology may provide patients and healthcare practitioners with a false sense of security about the reduction in the risk of anesthesia awareness," added MedPage Today (3/12, Gever). The results of the new study "contradict those of two earlier studies supported by Aspect Medical Systems, the manufacturer of the bispectral index monitoring system." In those trials, there were "major reductions in rates of awareness when anesthesia dosing was pegged to system readouts during surgery." The company's "literature says its monitor is now used in 60 percent of operating rooms in the United States."
In an accompanying editorial, Beverley A. Orser, M.D., Ph.D., professor of anesthesia and physiology at the University of Toronto, "says she is not surprised that the BIS monitor was no better than enhanced anesthesia monitoring at preventing waking during surgery," according to WebMD (3/12, DeNoon). Dr. Orser said, "I question the ability of this device to prevent anesthesia awareness because I don't think it is targeting the areas of the brain responsible for this activity."

'zilla

[swatsurgeon]

Back to Doc T's comment...the ICU has a different set of rules than the OR where you generally want patients DEEPLY asleep/sedated while unable to monitor reliable objective criteria that you generally can monitor in the ICU.. Another gadget with no class 1 data to support its use......
ss

[Red Flag 1]

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[swatsurgeon]

BIS has been around for some time. I have used it in surgery and found a bit of a time lag as I have said before. Patients on and off BIS have had recall...it is not an absolute indicator or predicter of awarness. A bit of a delima happens when you have 10 ORs running with general anesthesia, and only 6 BIS monitors. Who gets the BIS? Do I think I need one for me when I am under general anesthesia? Do I want my MD/CRNA looking at me or the monitor?

I have two fears with BIS monitors. One is that ICU /OR staff will run their eyes around the room at the monitors without really using a "clinical eye" for the patient...believing the monitors only and writting down the numbers. The second is that some day a case will be brought to trial and a provider ICU/OR will have to explain why a BIS was not used.

At one time every patient under anesthesia care, general, regional,MAC, had a precordial stethascope on their chest for their entire anesthetic. How often are they used today? Reliance is on PulseOX & EKG for pulse rate.

A monitor will likely be produced to give us a solid look at the awarness issue. BIS is on the track, just not totally there yet.

RF 1


RF 1,
you are right on......BIS is a tool and tools fail. Always have a back up that is as good as the original, be it monitoring of vitals, response to stimulation, other techno boxes with numbers/waves/info. I can't remeber if it was TS or TR that said always be prepared with your backup, build in redundancy since tools fail (paraphrasing one of these fine gentlemen). Great lesson to take to heart.

ss

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