Dr. Craig Weldon and colleagues from the University of Florida presented a thought provoking abstract at the ASA meeting, held this past October in Orlando. They recorded BIS monitor data on 907 adult patients undergoing elective general anesthesia anticipated to last at least 2 hours. BIS data were blinded to the anesthesia provider. While their results showed no difference in baseline BIS levels between survivors and non-survivors, logistic regression analysis revealed independent association between increasing age (p=0.001) and mortality and between lower BIS levels (p=0.001) and mortality. While it is very intriguing data, the reasons for this correlation are not clear and are not sufficient to establish causation. Dr. Terri Monk, one of the investigators, notes that it is possible that the lower BIS levels may be “simply a marker for patients who may be susceptible, within one year of surgery, to die of causes unrelated to their anesthesia, or that greater sensitivity to anesthesia is related to the co-morbidities in many of the patients studied . . . It is also possible that there is an unknown mechanism by which anesthesia exerts deleterious effects on certain patients postoperatively and contributes to increased mortality.” In addition to Drs. Weldon and Monk, other investigators on this team included Michael Mahla, MD, and Maria T. van der Aa, BS, all from the University of Florida. Financial support for this study was provided by the APSF and I. Heerman Anesthesia Foundations, Inc. BIS monitors were loaned and sensors were provided by Aspect Medical Systems.
Circulation 36,825 • Volume 17, No. 4 • Winter 2002