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Why should anesthesia providers be concerned about such a rare complication of anesthesia? Dr. Sebel: Because of the denominator. There are more than 20 million anesthesia cases annually in the United States, so a 0.13% incidence of awareness means approximately 26,000 cases of awareness every year, or an average of 500 every week. Dr. Sandin: In Sweden, with only 8 million people,we
have about 250,000 cases of relaxant "I think patients have traditionally been
Dr. Leslie: There are about 100 cases of awareness in the United States every day. If we were able to reduce that number, the amount of human suffering we could relieve would be very significant. When discussing awareness with anesthesiologists, they often say,"I've been doing this for many years and I've never had a case of awareness." They don't see it as anything but an extremely rare event. Dr. Sebel: The reason many anesthesiologists believe they’ve never had a case of awareness is that they don't go looking for it. One study by Moerman conducted in The Netherlands suggested that only 35% of patients who experience awareness ever report it to their anesthesiologist. To determine whether you've had a case of awareness, you need to ask patients on more than one occasion. It takes at least two interviews with a structured interview technique, like the one we used in our study, to determine accurately whether a patient experienced awareness. Dr. Sandin: Non-paralyzed patients usually respond to painful stimuli by moving, so they are more likely to receive additional anesthetic. However, some non-paralyzed patients do not move despite the fact that they are aware. These patients do not always communicate their episode of awareness because they may not have perceived it as a traumatic event - particularly if they found themselves quickly drifting off after becoming aware. If the patient experiences pain during surgery and cannot move or communicate, their agony will increase tremendously. Being unable to signal that you are aware is perhaps even more disturbing than pain itself. Some patients think they are dying. And that can lead to serious emotional and mental health problems afterwards. Even in these cases, we've found that the patient may not spontaneously communicate that they experienced awareness. Dr. Leslie: Let me share an anecdote that sheds some light on this and on the long-term adverse psychological effects of awareness. A friend of mine is a pediatric anesthetist in Melbourne who was asked to assist in a case involving a boy of about 8 or 10. The boy had had a previous surgery about a year prior and ever since his behavior had been terrible. His school performance was way down and his behavior made him difficult to handle. When he came in for the repeat head and neck surgery, my friend, who has an interest in awareness, asked the boy about his previous experience with anesthesia. The child looked at him and said, "Can you make sure you turn off my ears during the next surgery because I heard everything the doctors said during my last operation." Until then, no one realized this child had been aware during surgery. The incidence of pediatric awareness is probably higher than in adults because hemodynamics as an indicator of consciousness are even less reliable than in adults and there is a great deal of caution about overdosing children. Dr. Sebel, will it come as news to the U.S. anesthesia community that the incidence of awareness is as high as your study demonstrated? Dr. Sebel: To anyone who has been following the literature, the results of our study are exactly what would be expected. However, no one in recent years had established the incidence of awareness in the United States. Some anesthesia providers felt that the practice of anesthesia is different in the U.S. than in Europe, and that the incidence of awareness may be lower in the U.S. Well, our study demonstrates that it's not. Dr. Sandin, is awareness seen as a significant problem in Sweden? Dr. Sandin: Yes. Awareness has been an issue of great concern in the anesthesia community in Sweden for the past ten years or so, although there is no consensus on the best way to prevent it. But I think the data from our study and Dr. Leslie's in Australia support my view that brain monitoring can help clinicians reduce the incidence of awareness. Is it possible the incidence of awareness is even greater than that suggested by your respective studies? Dr. Sandin: I think so. In most awareness studies patients are interviewed only once, usually within 24 hours following surgery. What we found was the possibility of delayed memory in a substantial number of cases. I think patients have traditionally been reluctant to discuss awareness for fear of being regarded as abnormal or even crazy.
I think another problem is that doctors fear that if they raise the issue of awareness with patients post-operatively they'll be giving patients an opportunity to find an adverse outcome from their anesthetic. So it's not surprising to find anesthesiologists saying they've never had a case of awareness. If you're practicing in a major academic center with a wide range of sicker patients, you've probably had at least one case of awareness in the past year. Do cases of awareness suggest there is something wrong with the way people are practicing anesthesia? Dr. Sebel: No. There is a normal distribution of anesthetic requirement across the population. Not everybody needs exactly the same amount of anesthesia. Absent effective monitoring, you can't tell if your patient is inadequately anesthetized and at risk of awareness. Couldn't awareness be prevented simply by erring on the side of giving too much, rather than too little, anesthesia? Dr. Sebel: No, because patients aren't necessarily going to tolerate that. Increasing the concentration of anesthetics will result in other complications. The idea is to give the patient the right amount of anesthesia: not too little; not too much. Too much is more costly, dangerous, and you'd have an increase in the amount of nausea and vomiting and delayed wake-up. Dr. Sandin: There may be cases where large doses of anesthetics are justified, for example in a patient reporting previous awareness. Adopting this approach in broad practice would come at a high cost in prolonged recovery, less stable intraoperative hemodynamics, and other complications. If there's an alternative to industrial, huge doses of anesthetics, that is absolutely preferable. Dr. Sebel, in your study there were some patients who experienced awareness even though they were being monitored with BIS. How do you explain that? Dr. Sebel: Because our study simply sought to establish the incidence of awareness, there were no guidelines provided for those cases where the BIS Monitor happened to be in use. For example, in one case the patient who was aware had a high BIS value. The BIS Monitor doesn't prevent awareness by itself. It provides information that can help the clinician identify periods of increased risk of awareness. It's an important distinction. Dr. Leslie, in your study the patient cohort without BIS monitoring had 11 cases of awareness and the BIS monitored group, which was the same size, had two. These are relatively small numbers when you're talking about thousands of cases. Dr. Leslie: These numbers take on a new meaning when you consider how many patients are aware every day. We showed a five- to ten-fold reduction in the number of awareness cases. And, as has been said, this represents a large reduction in human suffering. We believe that the results of our study justify the expense of BIS monitoring to reduce the incidence of awareness in patients at high risk for awareness, quite apart from the other benefits of BIS monitoring. "We believe that the results of our study justify the How well accepted is the technology where you practice and how might your studies affect perceptions in your anesthesia community about brain monitoring? Dr. Leslie: The number of BIS Monitors in use in our region before the trial was very small, and only a minority of centers participating in our study had a BIS Monitor for any length of time before the trial. But as the trial progressed, there was a growing trend for the monitors to be used on patients who weren't part of the trial, particularly cardiac patients. People found it very useful in sorting out the causes of hemodynamic instability. Because we have a government-funded health care system, the data about BIS' delivery of cost savings associated with faster wake-up times and less anesthetic didn't have a big impact, though they are certainly important to the patient and for hospitals in other areas. There is a lot of interest here in the awareness data and the research now being done in the United States and Sweden that suggest over-sedation may be associated with higher postoperative mortality. Our study has started a push from the larger hospitals to get BIS Monitors, especially for use in high-risk patients. Dr. Sandin: Brain monitoring is still not used in the large majority of cases in Sweden, including cases of relaxant anesthesia. The attitude here has been wait and see. I think we may be at a turning point in this country now that we are able to present the data that it may be possible to reduce the incidence of awareness significantly using the BIS Monitor. Can the BIS Monitor be justified, from a cost standpoint or otherwise, simply because the information it provides can help reduce the incidence of awareness? Dr. Sandin: I think there is dual justification for increased use of brain monitoring in Sweden; reduction of the risk of awareness and the potential for more precise titration of anesthetics. Dr. Leslie: Based on the results of our trial, the cost of the BIS Monitor is justified to reduce awareness in high-risk patients, with no other objective in mind. When you consider the potential for prolonged post-operative psychiatric programs to treat post-traumatic stress arising from awareness, and in the U.S. the cost of potential litigation arising from a case of awareness, the investment in BIS to prevent even one case of awareness isn't a lot. But apart from awareness, the BIS Monitor is very helpful because it provides more information and often different information than observation of hemodynamic processes alone. For example, when you use an epidural in an elderly, beta-blocked patient, you can still manage the anesthesia with confidence while they're hypo- or hypertensive. Dr. Sebel: These three studies make a compelling case for the use of BIS Monitoring to reduce the incidence of awareness. But, you see, I have already decided that the BIS Monitor is worth having in every operating room, quite apart from the awareness issue. The awareness data simply strengthens the case for using BIS. "I use the BIS Monitor in every case because
Has your involvement in these trials impacted the way you practice? Dr. Leslie: Yes, in several ways. Most of the anesthesiologists in my hospital now include a discussion of awareness in the pre-operative interview, and while we were concerned that this would raise patient anxiety, we've found that we can allay that anxiety by explaining that we now have a monitor that helps reduce the incidence of awareness. A second change in my practice, apart from the fact that I now use the monitor for all patients at high-risk, is that I am more aware that I have to act on the information the BIS Monitor is giving me because I'm confident that it's telling me something important. I found that without BIS Monitoring there is a tendency to over-anesthetize patients. For example, when I started using BIS and giving patients what I thought was the proper concentration of anesthesia, patients' BIS values were in the 20s and 30s. Finally, I now conduct post-operative interviews where I ask a few questions to see if they have any recall. So, my participation in the trial has profoundly changed my practice. |
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anesthesia
every year, which means even in this tiny country we have hundreds
of cases of awareness every year. It’s not just the number
of cases that’s of concern. We have limited knowledge about
the degree of suffering patients experience when they endure this.
Yes, we know such patients often experience serious pain and severe
stress during the event, but there is also evidence that many are
at significant risk for Post-Traumatic Stress Disorder (PTSD) long
after the event. Some studies suggest that anywhere from 30 to 50%
of patients who experience awareness subsequently suffer significant
mental health problems. It’s a serious problem.
Dr.
Leslie: Anesthesiologists rarely ask their patients whether
they experienced awareness. For one thing, we seldom get an opportunity
to see our patients post-operatively because they go home, especially
in the current health care environment. And our schedules are such
that doing post-operative follow-up is difficult, so we usually
don't ask them. In my view, that's unwise because it's an important
outcome of our care. 
Dr.
Sebel: In my practice, I use the BIS Monitor in every case
because I think the benefits are clearly defined. If you look at
our three studies together it is clear that BIS monitoring, correctly
used, reduces the incidence of awareness.
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