Considerations before adopting new standards for monitors

            BIS and other Brain Function Monitors (BFM) have value but a careful analysis of the unbiased research that was not funded by industry does not support their routine use.  It is important to understand the history of the ASA Practice Advisory on the subject of awareness under anesthesia.  In appointing an independent group to review the literature, many of the key supporters of this technology were felt to have significant conflicts of interest related to both research support and honorarium for speaking from Aspect Medical.  Therefore, the debate about this technology must be viewed in the context of the scientific evidence and potential financial motivators.  After publication of the Practice Advisory, the American Society of Anesthesiologists concluded that the evidence on the value of the technology was insufficient and that a study should be conducted which was funded independently of Aspect Medical.  The ASA has now funded two large-scale studies on the use of brain electrical activity monitoring to decrease intra op awareness; the results of these studies are pending.  An additional trial without industry sponsorship has been completed and the results should be published shortly.  The findings of this trial will further our understanding of how this monitoring modality adds to what is currently available.

            Are their disadvantages or risk to adding this additional monitor?  This can be extrapolated to the question of whether all monitoring is good.  When I trained, the vast majority of patients with coronary artery disease undergoing major surgery had pulmonary artery catheters.  In fact, randomized trials were planned and could not be conducted based upon beliefs by the practitioners that it was unethical to randomize patients.  Propensity analysis was required of cohort studies to finally justify studying this monitor, and there are now several studies in different venues which suggest no benefit and potential harm.  As noted in other sections of the webblog there is a lot we do not know about depth of anesthesia and consciousness, and intra-operative recollection.  We also do not know how the BIS and other BFM respond to surgery and anesthetic drugs.  I therefore believe that there are indications for the BIS monitor, but that for the vast majority of cases we should focus on ensuring our patients are receiving adequate drug concentration (e.g. ET inhalational agent analyzers and good functioning IVs for TIVA), and that we do not rely on information from such monitors as false assurance that all is well.

Lee A Fleisher, M.D, FACC.

Robert Dunning Dripps Professor and Chair, Department of Anesthesiology and Critical Care, University of Pennsylvania