Waking During Surgery: Monitors May Not Help

Researchers say a brain monitor won't lower the chance of waking during surgery.

February 9, 2009, 2:12 PM

March 13, 2008— -- When Mark Rosen was being prepped for emergency chest surgery, he had every expectation that his experience would be the same as that of most other surgical patients.

Instead, Rosen, a 20-year-old college student at the time, endured a nightmare experience — one that was far from the norm.

"I knew something was wrong," he recalled, "feeling them cutting. I remember wanting to push away, but you're paralyzed. You can't move, you can't open your eyes … the fright of being locked in."

Now a doctor, Rosen, ironically enough, is the vice chairman of anesthesiology at the University of California San Francisco Children's Hospital. He said his chosen career path was not a result of his terrifying memories, and he underscored the fact that cases such as his are, thankfully, few and far between.

But new research suggests that in the rare instances when a patient does become aware during surgery, a brain monitor specifically intended to alert doctors to this phenomenon is not doing its job.

In the study, published Wednesday in the New England Journal of Medicine, researchers looked at nearly 2,000 surgical patients at the Washington University School of Medicine who were determined to be at high risk of waking up during surgery. Half of the patients were monitored during surgery with a Bispectral Index System (BIS), while the other half were monitored using a different method.

BIS, also known as "the BIZ," reads brain waves from a sensor placed on the forehead and displays a score to help doctors give the best dose of medications to keep their patients sound asleep.

What the researchers found was that BIS did not increase the likelihood that doctors would be able to tell if a patient was regaining awareness during surgery.

"Reliance on BIS technology may provide patients and health care practitioners with a false sense of security," noted lead study author Dr. Michael Avidan of the Washington University School of Medicine.

Before this study, many doctors, including Rosen, were already skeptical of BIS.

"I applaud this study for convincingly revealing the BIS monitor for what it is … unreliable for clinical practice," Rosen said, adding that doctors may use this type of technology during brain, spinal, or certain vascular surgeries. But even then, "they aren't used to assess depth of anesthesia."

The study also questions whether BIS is worth the cost.

Avidan and his colleagues noted in the study that 23 million patients in operating rooms worldwide have been monitored with BIS. Using this system for all patients, the authors continued, the cost of the disposable forehead sensors alone would exceed $360 million every year.

Many anesthesiologists agreed that there are better tools to keep patients asleep during surgery.

"Because awareness is rare, the BIS monitor [is unreliable], and the use of the monitor is relatively costly," said Dr. Brad Hindman, professor of anesthesia at University of Iowa. "It is hard to justify the use of these monitors solely on a cost-effectiveness basis."

But in spite of this, many patients may still be driven by fear and horrifying media portrayals to request the monitors … regardless of whether they really work or not.

"The simplicity of the concept, together with the showcasing of patients who have had awareness… has contributed to a demand from patients for use of this technology," noted Dr. Beverley Orser, assistant professor of anaesthesia at the University of Toronto in Canada, in an editorial that accompanied the study.

But while many surgical patients worry about being awake while under the knife, doctors say this is extremely rare.

The Joint Commission, a regulatory committee that monitors safety at hospitals, reports that between 20,000 and 40,000 cases of anesthesia awareness may occur every year in the United States. The numbers sound high, but they are dwarfed by the number of people have surgical procedures in the country every year … about 21 million.

"Only 0.1 percent to 0.2 percent of patients actually have the experience," said Dr. Ronald Emerson, a neurologist at Columbia University Medical Center (CUMC).

In short, this means you have a far better chance of getting hit by a car than waking up during surgery.

"Many patients are concerned this will happen to them, but very few will experience intra-operative awareness," agreed Dr. Eric Heyer, a neuroanesthesiologist at CUMC.

And awareness during surgery may not always mean experiencing the pain of surgery. Dr. Elliot Krane, a professor of anesthesia at Stanford University School of Medicine, explained that most cases "are really the recall of memories before the full anesthetic dose had been administered prior to surgery, or are memories during emergence from anesthesia after the completion of surgery … when awareness occurs in these and other rare circumstances, it is seldom associated with pain."

So while medical technology has made many advances to keep patients safe in the operating room, it may never replace the medical training and experienced judgment of doctors.

Waking up during surgery is rare, and, as Dr Heyer put it, doctors are "doing their best to make it even rarer."

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