It's easy to be squeamish about going under the knife, especially if you fear that the anesthesia might forsake you. Well over 20,000 people a year, by some estimates, experience "anesthesia awareness," in which they awaken during the operation, paralyzed but later able to bear witness to operating room chatter, the clanking of instruments, and the sucking, sawing, or slicing sounds of the surgical team at work. Most of the time (but not always), there is no physical pain and the patient later recalls only fleeting awareness. But sometimes the event leads to post-traumatic stress disorder and lingering terror about hospitals and operations. How disappointing, then, that a study just out in the New England Journal of Medicine finds little value in a technology that might prevent this unhappy complication.
The technology, called the BIS (short for "bispectral index") monitor, measures the brain's electrical activity and comes up with a single number to represent the level of consciousness, ranging from 100 for fully awake to 0, no brain activity. Amid growing recognition that intraoperative awareness is a worldwide phenomenon, many countries, including the United States, have witnessed a proliferation in the use of such monitors to better titrate drugs, with reported success. But this new trial from the School of Medicine at Washington University in St. Louis of 1,941 patients at high risk for awareness showed no added value when BIS was used along with standard practice. The study is small, however, and the awareness events rare—only two definite instances in the BIS group—so let's not be too hasty in slamming the technology just yet.
What the study shows, first and foremost, is that anesthesia is still more about clinical sense than gadgets, says Nagy Mikhail, an anesthesiologist and pain specialist at the Cleveland Clinic. Historically, it has been difficult to determine the depth of anesthesia. What may look like a gentle slumber is in fact a complex mix of states—unconsciousness, paralysis, insensitivity to pain, and inability to remember—that can vary inexplicably from one patient to another. It takes skill and judgment, says Mikhail, to determine the appropriate level of drugs. That means continuously looking at the whole patient, through physical examination; monitoring of oxygen levels, heart rate, blood pressure, and EKG; and tracking the concentrations of anesthetic gas in exhaled breath. A racing heart or a flurry of irregular extra heartbeats, changes in the pupils, perspiration, or even a tear can signal inadequate depth of anesthesia in a paralyzed patient.
But brain monitoring can be helpful as a complementary tool. It adds one more physiological measure and has proved to be particularly useful when intravenous sedation is the only anesthetic as compared with inhaled gas, which can be readily monitored. And a failure to promptly lower the BIS score into the range of 40 to 60 is certainly a sign that the anesthesia delivery equipment may be malfunctioning, one cause of intraoperative wakefulness.
Sentinels. Most hospitals have become vigilant about what previously might have gone unnoticed or been dismissed as a bad dream. Some regularly interview patients about their anesthesia experience, and the American Society of Anesthesiologists advises that in documented cases, awareness patients should be offered psychological counseling. The Joint Commission, which accredits hospitals, considers awareness a "sentinel event," calling for immediate investigation and response. This reinforces some obvious advice: If you are facing surgery, make sure you know the skill and experience of your anesthesiologist.
However chilling, awakening during an operation has to be kept in context. There are over 20 million general anesthesias nationwide every year, and more than 99.8 percent of patients remain wholly unaware. On that score, some worry that the recent film Awake, a wild medical psycho-thriller centered on anesthesia awareness, will frighten more than it entertains. The protagonist, a 22-year-old multimillionaire, is paralyzed but conscious during his heart transplant and overhears his surgeon talk about a scheme to do him harm. An anesthesiologist, new to the case, conveniently stumbles into the OR in the middle of the surgery and picks up on the awakening when he sees the patient's tears. Without giving away more of the plot, I can safely say there is a bit of reality here: The anesthesiologist, not a brain monitor, saves the day.