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Awareness: “The risk varies depending on the research“
Assistant Professor Doctor Ingrid Rundshagen;
As a patient about to go under general anesthesia for surgery, you are understandably nervous. Although complications in anesthetics have become rare, patients still fear two things in particular – to not wake up again after the surgery or to wake up during the surgery, respectively. The latter phenomenon is called awareness or also intra-operative awareness.
But how often does it really happen that patients witness moments of the surgery and how does medicine try to prevent this from happening? MEDICA.de checked with Assistant Professor Doctor Ingrid Rundshagen, Head of Department and Anesthesiologist at the Charité University Hospital Berlin.
MEDICA.de: Doctor Rundshagen, how do you define awareness?
Ingrid Rundshagen: Awareness is a synonym for intra-operative awareness, this meaning an unwanted experience of being alert during general anesthesia. If we want to describe it, we typically refer to patients being able to recall events that happened while they were under anesthesia, after they wake up from anesthesia.
MEDICA.de: This means patients talk about actual experiences?
Rundshagen: That’s correct. There are patients who after a surgery voluntarily or on inquiry report different events. In those patients that can actively remember things, we say that the explicit memory function remained during anesthesia. This results in them being able to talk about it later on.
MEDICA.de: How often does this happen?
Rundshagen: That depends on the group of patients you investigate of course. Generally in adults a risk between 0.1 and 0.2 percent is assumed – this equates to one to two patients in a thousand. Of course the risk varies depending on the research. There are International studies that turned out significantly lower numbers. And then there are groups of patients, where the risk needs to be rated higher. Female patients who undergo a C-Section for instance and require general anesthesia should be mentioned here.
MEDICA.de: Some patients report pain that they trace back to awareness, without them actually being able to remember an experience. How is this possible?
Rundshagen: Our memory is very intricate. For instance, we possess a so-called implicit memory. Here you can find memory content that we don’t remember consciously, but that can be evoked by using specific tests. For the topic of awareness for example, there was an experiment where the story of Robinson Crusoe was read out loud during surgery. Patients had no memory whatsoever about this after the surgery. But in a postoperative test they were confronted with this by them having to spontaneously associate something with the term ’Friday’ for instance. The idea was to probe through associations whether instead of the weekday the character of Friday would be mentioned more often, since the typical spontaneous word association would be: Friday is a weekday. To identify implicit memories, you therefore need to utilize specific tests. This is why it could actually be that a patient thinks he noticed something, but cannot actually talk about it.
MEDICA.de: Should you actually even look into such assumptions?
Rundshagen: This depends on whether this is something that bothers the patient or constricts him, respectively. We know nowhere near as much about sustained memory functions in anesthesia with implicit memory as we do about those of explicit memory. But if patients have an explicit memory, meaning they talk about awareness of their own volition or on inquiry are able to give detailed descriptions, there definitely is a need for action.
MEDICA.de: How do patients describe their experiences?
Rundshagen: This varies a lot. It can be that patients think they have heard or seen something, for example conversations or the light in the operating room. But this does not necessarily mean that they feel disturbed by this experience. However, if this is more distinct, it can happen that patients are in pain or they fight the feeling of not being able to move.
MEDICA.de: How do you determine awareness during surgery?
Rundshagen: There are only indirect references. You certainly become very observant, if there are problems during drug administration. There could be an issue, if the vein that is used to administer the drugs during surgery, bursts during the course of infusion. This prevents the anesthetic from properly getting into the body. Or an instrument is turned off, although you actually did not want to switch it off. This unfortunately happens. In these cases you would later actively ask whether the patient had any problems. However, the patient is continuously being clinically monitored during the anesthesia of course. This means the anesthesiologist constantly checks the function of the cardiovascular system, checks the pupils and for instance also checks whether the patient perspires. Aside from that, there are specific devices, so-called depth-of-anesthesia monitors. These instruments intraoperatively measure the patient’s brain activity, which we know is being specifically affected by anesthesia. There are mathematical algorithms that are being underlaid and specific critical values, within which the depth of anesthesia should remain. If the device signals deviations, you would look into those. Typically, you intraoperatively interpret many different items to deduce awareness.
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MEDICA.de: Is this depth-of-anesthesia equipment well established in German hospitals? Do you use such a device?
Rundshagen: So far they are not recommended as a standard for performing general anesthesia in Germany. That is to say, you don’t have to use them, but you can. However, there are still some questions that need to be answered in terms of the monitors and are still being controversially discussed by the corresponding body of experts. All that said: We use them under certain conditions, but we don’t use them routinely for every anesthesia.
MEDICA.de: When you say controversially discussed: What are some of these questions that are being talked about?
Rundshagen: There are specific factors that can also influence EEG signals. There are a number of error sources that need to be eliminated. Current analysis of large patient populations confirms: Although thanks to the monitor in individual cases you can definitely identify that the anesthesia is perhaps too light, but you cannot conclude from this that the patient will recall an awareness experience postoperatively. This correlation is not given. It was discovered that the monitoring does not act preventatively. But this was the expectation: You use the monitors and have a hundred percent certainty.
MEDICA.de: How do you prevent a patient from waking up during surgery?
Rundshagen: There are recommendations from the study group at the American Society of Anesthesiologists on how to minimize the risk for patients. Trivial things like checking your instruments and anesthesiological equipment are among them as well as taking an exact medical history of the patient. There also is a recommendation to very closely adjust the equipment’s alarm limit. And this is something that is not done in everyday life in every hospital. This needs to be very clearly stated. Ultimately, there are a lot of little things you can do to achieve a safety standard for the patient that’s as high as possible. This also includes for instance syringe infusion pumps that signal at an early stage if the infusion is no longer running appropriately.
MEDICA.de: How well is awareness or intra-operative awareness, respectively, researched?
Rundshagen: There are more and more studies on the subject. The first cases obviously are as old as general anesthesia itself. The first reports refer to surgeries that happened more than 150 years ago. There were patients which reported that although they had no pain, they still witnessed that something was being done. Not until the past 50 years, awareness is indeed being researched as a scientific phenomenon. Undoubtedly this is also due to the fact that other serious complications while inducing anesthesia thanks to today’s standards, have become less frequent. And so the focus increasingly is on the quality of administering anesthesia.
MEDICA.de: There is a study by the University of Louisville from 20021, which investigated the susceptibility to pain in red-haired people. The conclusion: redheads are said to be more sensitive to pain and thus require higher doses of anesthetics. Would this group of people consequently also experience more frequent cases of awareness?
Rundshagen: In the studies that I am familiar with, the criteria of hair color was not being considered. So to be fair I have to say that I cannot really answer this particular question. But if it was the case that red-haired patients definitely needed more anesthetics and you are also able to quantify this, then of course you should keep that in the back of your mind.
The Interview was conducted by Simone Ernst
(Translated by Elena O'Meara)
1: Liem, Edwin et.al: Anesthesiology: August 2004 - Volume 101 - Issue 2 - pp 279-283 – Anesthetic Requirement Is Increased in Redheads