WATERLOO - On the day of his heart surgery in April 2006, Tom Hagarty went under general anesthesia at 6 a.m. and woke up at 11 p.m.

While doctors at Allen Hospital worked to unblock five of his arteries, the Cedar Falls City Council representative remained unconscious.

"It's a day that you forget," said Hagarty. "You're just out."

That's the way general anesthesia is supposed to work. And most patients who receive sedation medications during surgery have no recollection of their time in the operating room. But a small percentage of people experience awareness under anesthesia.

The condition ranges in severity, according to the American Society of Anesthesiologists. Some patients recall their surroundings, or may catch snippets of operating room conversations. In the most extreme cases patients feel pain, but are unable to communicate their distress to their doctors. That disturbing scenario is showcased in the film "Awake," released last week.

In the movie, a man's anesthetic fails during his open heart surgery. He is alert, but paralyzed, and cannot tell his physician he is suffering.

"It's a very unfortunate condition and it is recognized as a highly traumatic psychological event," said Dr. Ashar Afzal, an anesthesiologist with Cedar Valley Medical Specialists. "But it's not a very common problem given the hundreds of thousands of surgeries that are performed across the world and across the country."

Medical professionals don't agree on how often the condition occurs. The American Association of Nurse Anesthetists estimates that one in 1,000 patients have some level of awareness during general anesthesia, but note that in most cases the experience is fleeting and does not include pain. The American Society of Anesthesiologists believes that one out of every 10 patients become aware during surgery.

No one knows why some patients become alert during surgery.

"People are doing research on that," Afzal said. "So far there is nothing anyone has found that can pinpoint the cause of awareness during anesthesia."

In some trauma cases or emergency Caesarean sections, awareness cannot be prevented because administering a full battery of sedation drugs would compromise the patient's health, stated Mark Odden, who owns an anesthesiology company in Manchester. In most cases, the proper administration of sedation medications protects against awareness.

"Anesthesia changes minute-to-minute, second-to-second - deepening and lightening, deepening and lightening throughout the procedure," said Odden, a certified registered nurse anesthetist. "As we see changes in (a patient's) vital signs, we'll adjust the medication."

A fear of becoming aware during anesthesia should not keep people from following through with recommended surgical procedures, said Dr. David Lane, Wheaton Franciscan Healthcare chief anesthesiogist.

If you have experienced awareness in the past, talk to your anesthesiologist before the procedure. In some cases your doctor can use other medications, including local anesthesia or regional anesthesia, in place of general anesthesia. Awareness is expected with those alternative drugs, but if patients experience pain while under those medications they can immediately communicate their discomfort.

Still, the majority of patients undergoing surgery choose general anesthesia and have no memory of their time under the knife, Lane said.

"Most of the time, people don't want to be awake during surgery," he said. "They want go to sleep and when they wake up it's over."

Contact Mary Stegmeir

at (319) 291-1482

or mary.stegmeir@wcfcourier.com.

Have you experienced awareness under anesthesia?

If so, the American Society of Anesthesiologists would like to hear from you. The organization is collecting information to determine how the condition occurs and how to prevent it from happening to other patients.

For more information call (206) 616-2669 or visit http://depts.washington.edu/awaredb/.