During general anesthesia, a surgical patient needs to be given a combination of drugs that ensures four basic things: 1) immobility 2) muscle relaxation 3) hypnosis, and 4) amnesia. The first two are the chief concerns of the surgeon, but the most pressing one for the patient is the last one. I get asked by patients about it almost every day. "I'm not gonna remember, am I?" My answer is always the same - not if I can help it.
I have been an anesthesiologist for a decade now, and I have yet to have an incident of intraoperative awareness that I know of. However, it is a well documented phenomenon, and one that is a big problem for people who have experienced it. I have interviewed a few patients who remembered being awake during surgery, and though a few were nonchalant about it, most were absolutely horrified by the experience, and for good reason. Imagine it - you're having surgery, you can't move, and you are (supposedly) unconscious. Yet you remember incidents during your operation, including being cut open, or people talking about you. Worse yet, you feel pain but can't do anything about it. Just thinking about it is nauseating, and I wouldn't wish it on my worst enemy.
There are a few things I want to discuss regarding this phenomenon. First, how often does it happen? Second, when does it happen? Third, how (in the world?!?!) could any anesthesiologist let it happen?
Incidence:
There have been numerous studies documenting how often recall under general anesthesia occurs, and they vary. Some cite an incidence of up to 0.9% - almost 1 in a hundred. That's a lot. There was a more recent study from the University of Illinois at Chicago that looked at almost 180,000 patients over a three year period that had undergone general anesthesia. They found an incidence of recall of about 0.006%, or 1 in about 14,500. That's not a lot - but try telling that to the one person out of that 14,500 who was awake during surgery. I'm more inclined to believe the more recent study, as anesthetic techniques have changed over the years and we have a wide range of drugs at our disposal to ensure amnesia.
When (and how) it happens:
Type of surgery
Not all general anesthetics are the same from the standpoint of recall. There are some cases where the risk of being aware during anesthesia is significantly higher than in others:
1. Cardiac surgery - A lot of the first documented widespread episodes of intraoperative awareness were during open heart surgery. I don't remember the statistics, but it's more than the 0.9% cited in previous studies on all general anesthetics.
2. C-sections under general anesthesia. General anesthesia presents a unique dilemma during a c-section. Of course, the woman in such a situation needs to be asleep to get her baby out. The problem is afterwards; the gases used in general anesthesia tend to relax the uterus. This may be a good thing when the obstetricians are trying to remove the baby, but afterwards, those relaxing properties prevent the uterus from contracting, and this can increase the risk of bleeding. So the anesthesiologist is limited in how much anesthetic gas they can use.
3. Trauma surgery - The problem here is the condition trauma patients are in when they arrive to the OR. They are unstable, with low blood pressures. Most of the anesthetic drugs we give tend to lower the blood pressure, so if a patient comes in with a blood pressure of 60 over 40, for example, the last thing we should do is make it even lower with anesthetic drugs.
4. Emergency surgery, of any kind. The same logic applies here as in trauma surgery. A person having emergent surgery is unstable and tolerates even a small amount of anesthesia very poorly.
Type of patient
Not everyone is at the same risk for remembering stuff during anesthesia. If you fit into one of these categories, be aware that your risk is greater:
1. Users of alcohol and drugs. This makes total sense, doesn't it? If someone drinks a lot of alcohol or uses drugs of any kind, they have a greater tolerance to anesthesia. This doesn't just apply to street drugs like heroin or cocaine. It applies to prescription pain meds (like Vicodin or Oxycontin) and prescription sedatives/anti-anxiety drugs (like Valium or Xanax). People who use these drugs are just a little different from the rest of us. For one, their livers are turbocharged and spit out anesthetic drugs quickly. For another, their brain cells have fewer receptors for anesthesia drugs, so it takes more drug to affect those brain cells.
2. People on antidepressants. See above. These drugs tend to make the liver metabolize drugs faster.
3. People who have had similar episodes before. Another intuitive one. If, for some reason a patient was aware during anesthesia even though everything sounded OK medically, there's probably something going on with that patient. We don't know exactly how these anesthetic gases work; as such, it's hard to predict how or why some people just aren't as affected by them as others.
4. People who have been told that they might be aware during anesthesia. No one is sure why that is; I suppose you could look at it as a self-fulfilling prophecy kind of thing.
5. Redheads. What?!?!? Seriously? It has always been a unwritten rule, especially among the older anesthesiologists, that redheads need more anesthesia for reasons no one knows. I always dismissed these old geezers as a bunch of idiots, but a study came out in one of our major journals in the last few years, and it backed it up. Granted, the study was very small, but it did show that redheads needed significantly more inhaled anesthetic gas (up to 20% more!) to maintain the same level of anesthesia as non-redheads. Believe what you may, I guess. I'm just putting it out there...
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