Last week, researchers published in the New England Journal of Medicine the results of one such effort, which failed to show a distinction between two commonly used measurement methods.
Researchers at Washington University School of Medicine, the University of Chicago and the University of Michigan, led by Professor of Anesthesiology Michael Avidan, compared two methodologies used by some hospitals to detect patients' surgical awareness in 6,041 randomized patients, all at high-risk of surgical awareness.
The standard method, which monitors end-tidal anesthetic agent concentration or ETAC, was compared with a newer and more expensive bispectral index or BIS, which detects brain electrical activity through the use of a commercially available sensor and an EEG. The BIS had been touted as superior.
Patients were interviewed within 72 hours after their surgery and at 30 days after extubation to determine their memory of the period between "going to sleep" and "waking up."
"Contrary to expectations," the researchers wrote, "the superiority of the BIS protocol was not established," as fewer patients in the ETAC group than in the BIS group experienced awareness.
In an accompanying editorial Gregory Crosby, MD, of the Department of Anesthesiology at Brigham and Women's Hospital in Boston, wrote that the findings "are disappointing but not surprising.