More Patients Awake During Surgery Than Once Thought

Unintended Awareness – or <"">Anesthesia Awareness – is a terrifying phenomenon affecting one or two of every 1,000 surgical patients.  That’s about 100 patients daily and 30,000 Americans annually.  Unintended Awareness is when a patient wakes during surgery.  When this occurs, patients can feel excruciating pain without being able to move or cry out and involves patients having some recollection of surgical events.  It is more likely to affect children and occurs in patients whose condition is unstable or in emergency or trauma situations.  Patients who experience Anesthesia Awareness may develop acute distress and emotional reactions and later onset of long-term psychological effects.

Most surgical anesthetics consist of a cocktail of drugs:  A sleep agent, painkiller, and paralyzing agent.  When the paralytic works, the patient is unable to speak or move and advise doctors that the sleep agent has failed.

Experts believed special brain-wave monitors were the best way to prevent Anesthesia Awareness.  Now, the first large, independent test of the monitors shows no improvement over older technology.  Researchers at Washington University School of Medicine in St. Louis compared two groups of about 1,000 patients each, all deemed at high risk for Anesthesia Awareness.  One group was fitted with the leading brain-monitoring system, which uses electrodes on the forehead to measure brain waves and software to calculate likelihood of consciousness.  The other used an older device that analyzes exhaled anesthetic gas.  Anesthesiologists watched for movement and changes in vital signs and followed protocols to maintain patients’ depth of sleep, adjusting anesthesia levels as needed.  Patients were interviewed after their surgeries about what they remembered.  Two people in each group experienced awareness; the two with the newer system felt pain as well.

Lead researcher Dr. Michael Avidan said that in two of those cases—one with each system—monitors indicated no problems; in the other two cases, monitors signaled problems.  The position of the anesthesiologists group has been that brain wave monitoring should not be done routinely, but may be helpful for certain patients at high risk of awareness.  Widespread use would be very costly.

Aspect Medical Systems, a large brain wave monitoring system maker, says its device, the bispectral index or BIS, is used in about 17 percent of the nearly 20 million annual US surgeries in which anesthesia gas is used.  The BIS can cost as little as $5,000; however, researchers estimate if it were used on all US patients receiving general anesthesia, the disposable electrodes alone would cost over $360 million yearly.  The device, on sale 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” said Aspect’s medical director, Boston anesthesiologist Dr. Scott Kelley.

Avidan’s fellow researcher, anesthesiology professor Dr. Alex Evers, said having doctors closely follow a protocol to maintain patients’ depth of sleep was key to reducing Anesthesia Awareness in both groups.  In 2005, guidelines were developed and approved that established protocols to help ensure proper anesthetic dosing and stated doctors should keep watch for Unintended Awareness by checking clinical signs such as movement and using conventional monitoring systems such as electrocardiograms, blood pressure monitors, and heart-rate monitors.

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