There's been growing concern in recent years about the sometimes-nightmarish phenomenon of patients waking up in the middle of surgery even though they are supposed to be under Anesthesia.

In April, the president of the American Society of Anesthesiologists responded to media reports about a West Virginia man who said he was psychologically traumatized by such an occurrence of awareness under Anesthesia.

In a letter, ASA President Mark Lema reassured the public doctors were working to determine how widespread the problem is and the best way to prevent it.

Dr. Frederick K. Ernst of Hoover has been practicing Anesthesia for 40 years, and is also an author, patient advocate and expert witness. Here is his opinion on Anesthesia risks and the possibility of awakening during surgery:

For many people, the scariest part of any surgery is Anesthesia. Is that fear well-founded?

It's a valid fear. Depending on the type of Anesthesia you give, you are very often taking people as close to death as they can get without actually getting there. So there's a fine line.

Granted we have come a long way in safety for Anesthesia during my 40-year career. Back in the 1960s when I first went into Anesthesia, the anesthetic mortality was 1 in 35,000. Now it is 1 in 200,000 to 250,000. It's a lot safer, but that's not to say that unfortunate events don't happen, because they do.

What is the most common error that occurs with Anesthesia? It's probably giving too much or not monitoring it closely enough.

I guess to put it into perspective, one of the two most outstanding teachers I had in Anesthesia was the doctor I studied under in Dallas for my pediatric fellowship. He used to say many times, "If you don't give Anesthesia like an old woman, you're going to get in trouble someday."

He meant that if you are not ... persnickety about how you give Anesthesia, you're going to get in trouble because you're going to forget to do something, you're not going to be paying close enough attention.

For example, awareness under Anesthesia that we're seeing so much more of today is a combination of the agents that we have that are more insoluble, and Anesthesia personnel are not paying close enough attention to what is going on.

How much more awareness under Anesthesia are we seeing?

The ASA admits to one-tenth to two-tenths of a percent of all general anesthetic patients experiencing awareness. In 2005 we gave between 20 and 21 million general anesthetics. That means between 20,000 and 40,000 cases of awareness under general Anesthesia were experienced.

And if you start talking to some of these people who have had this ... a lot of these people are experiencing severe post-traumatic stress disorders, and have trouble sleeping.

So waking up and finding somebody operating on you is a psychologically damaging experience?

Being paralyzed is part of it since you can't let people know, "Hey, I'm awake guys. I'm feeling this. I'm hearing you. Get me under." Is there anything a patient can do to prevent this?

There are certain conditions that make one more susceptible to awareness under Anesthesia. There are certain surgical procedures, and there are certain anesthetic techniques, that tend to make the occurrence statistically more common.

As a patient, know these and discuss these with your Anesthesia provider. Just say, "I want to ensure that I have absolutely no recall under Anesthesia."

For example, if you're someone who abuses prescription pain drugs, or you're someone who is being treated for chronic pain with opiates, this makes you much more susceptible to awareness because of polypharmacology.When you're putting the Anesthesia drugs on board ... you don't really fully know where that patient is.

Then, you can request and ensure that you have the brain monitor done on you to help show where you are in you anesthetic depth, although the studies are somewhat conflicting on this. That is one reason why the ASA has been slow in giving support to this brain monitoring device, and there are four or five different ones out there.

Some of them show too many false positives or too many false negatives. But the ASA a year ago came out with a modified opinion about the use of it, and on a case-by-case basis the anesthesiologist makes the decision.

If you're going to have general anesthetic and you're going to have a muscle relaxant on board for a major part of that surgery, then you really want to have brain monitoring. On the Web: American Society of Anesthesiologists, www.asahq.org

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• Lack of or Improper Use of Anesthesia
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General information about anesthesia including basic overviews, research, and additional resources.