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Monitors Don’t Stop Patients From Waking During Surgery

March 13, 2008

Researchers at Washington University School of Medicine in St. Louis reported disappointing results in a study on the prevention of anesthesia awareness,  which occurs when a patient under general anesthesia remains awake during surgery.

Patients in this state can often recall surroundings, events, and pain related to the surgery, even though they are under general anesthesia.  Because neuromuscular blocking agents are routinely used with general anesthesia, patients are often unable to communicate with surgeons when this occurs.

Testimonials from patients who have experienced anesthesia awareness say it’s as though they were trapped in a corpse, having awakened during surgery unable to move or speak.   Some remember hearing their surgeons talk, and in more serious cases even recall feeling intense pain.

Until now, experts believed special brain-wave monitors were the best way to prevent the situation.   But after the first large, independent test of the monitors by the Washington University researchers, it appears the monitors are no better than older methods of preventing anesthesia awareness.

In the study, researchers compared two groups of 1,000 patients having surgery at the university’s partner hospital, Barnes-Jewish in St. Louis, during 2005 and 2006.  The patients were all considered at high risk of waking up during surgery because of medications, health conditions or other factors.

One group used the brain-monitoring system, in which electrodes placed on the forehead measured brain waves and used software to calculate the likelihood of consciousness. The other group used an older device that analyzed exhaled anesthetic gas.

Anesthesiologists watched for movement and vital sign changes and followed protocol to adjusted anesthesia levels as needed to maintain the patients’ depth of sleep.  After their surgeries, patients were surveyed about what they remembered.

The results showed that two people within each group experienced awareness, with the two using the new brain monitoring system reporting having felt pain as well.  Dr. Michael Avidan, the study’s lead researcher, said that in two of those cases, one with each system, the monitors indicated no problems with the anesthesia. In the other two cases, the monitors indicated problems.

Statistically, anesthesia awareness occurs in 1 to 2 out of every 1,000 surgical patients, possibly more often in children.  It is believed to happen to approximately 30,000 Americans each year.

Some who experience the condition experience only vague, fleeting memories of things they heard, but others describe “white-hot pain” and terror, causing long-term emotional problems.

In an Associated Press report, Carol Weihrer of Reston, Va., said that 11 years after awakening during eye surgery she still suffers from post-traumatic stress disorder, can sleep for only short periods of time, and experiences mood swings and panic attacks.  She recalls during her surgery hearing the doctor give instructions, “Cut deeper, pull harder”¦..I actually saw them cut the optic nerve when everything went black,” she said.   

“While you’re laying there on the table,” she recalled, “you are thinking, praying, cursing, plotting, pleading, trying to crawl off the gurney, trying to kick, scream, move any part of your body to let them know you’re awake. In effect, you are entombed in a corpse.”

Weihrer has since founded the group Anesthesia Awareness Campaign.

Kathy LaBrie of Nashua, N.H., also suffered awareness during surgery for a deviated septum.  She remembers hearing “the sound of pushing and grinding and the surgeon talking to the nurses about the kind of car he had. … I tried moving my arms and legs, I couldn’t do anything. I thought I was dying.”

American Society of Anesthesiologists president Dr. Jeffrey Apfelbaum, who was not involved in the study, told the Associated Press there is “tremendous pressure” from industry and patient advocates to use the brain-wave technology, despite the lack of concrete evidence that it works better than older methods.

The anesthesiologists group’s position has been that brain-wave monitoring should not be done routinely as widespread use would be very costly, but it may be helpful for certain high risk patients.

Aspect Medical Systems, the leading maker of brain-wave systems, says its bispectral index (BIS) monitor is used in 17 percent of the roughly 20 million U.S. surgeries each year in which anesthesia gas is used.   

About 10 percent of U.S. surgical patients receive intravenous anesthesia without any gas, and the study results do not apply to these patients.

The device can cost as little as $5,000, but the researchers speculated that if it were used on all U.S. patients receiving general anesthesia, the costs of the disposable electrodes alone would exceed $360 million annually.

The monitor, available since 1998, “can prevent both too little anesthesia, which could cause awareness, and too much anesthesia, which could cause prolonged recovery and anesthetic side effects” such as grogginess and nausea, said Aspect’s medical director, Boston anesthesiologist Dr. Scott Kelley, in an Associated Press interview.

The new results show the system can allow anesthesiologists to “achieve a very low incidence of awareness in high-risk patient,” he said.

But Dr. Alex Evers, anesthesiology professor and Avidan’s fellow researcher, believes having doctors follow strict procedures to maintain patients’ depth of sleep was the key to reducing anesthesia awareness in both groups.

The Food and Drug Administration (FDA) has only stated that the BIS monitor  “may be associated” with reducing awareness during surgery.

Dr. Douglas Jackson, assistant anesthesiology professor at University of Medicine and Dentistry of New Jersey in Newark, told the AP that the study’s results show the BIS system “is not a magic bullet.”

“We still don’t have a monitor that can tell us about depth of anesthesia (and) awareness,” he said, adding that controlling it is still an art at this time.

On the Net:

The study was published in Thursday’s issue of the New England Journal of Medicine.  A summary of the report can be viewed at http://content.nejm.org/cgi/content/short/358/11/1097.

Washington University School of Medicine

American Society of Anesthesiologists

Aspect Medical Systems

Anesthesia Awareness Campaign




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