Estimation of the Bispectral Index by Anesthesiologists An Inverse Turing Test
ABSTRACT Processed electroencephalographic indices, such as the bispectral index (BIS), are potential adjuncts for assessing anesthetic depth. While BIS® monitors might aid anesthetic management, unprocessed or nonproprietary electroencephalographic data may be a rich source of information for clinicians. We hypothesized that anesthesiologists, after training in electroencephalography interpretation, could estimate the index of a reference BIS as accurately as a second BIS® monitor (twin BIS®) (Covidien Medical, Boulder, CO) when provided with clinical and electroencephalographic data.
Two sets of electrodes connected to two separate BIS® monitors were placed on the foreheads of 10 surgical patients undergoing general anesthesia. Electroencephalographic parameters, vital signs, and end-tidal anesthetic gas concentrations were recorded at prespecified time points, and were provided to two sets of anesthesiologists. Ten anesthesiologists received brief structured training in electroencephalograph interpretation and 10 were untrained. Although electroencephalographic waveforms and open-source processed electroencephalograph metrics were provided from the reference BIS®, both groups were blinded to BIS values and were asked to estimate BIS.
The trained anesthesiologists averaged as close to or closer to the reference BIS® compared with the twin BIS® monitor for 34% of their BIS estimates versus 26% for the untrained anesthesiologists. Using linear mixed effects model analysis, there was a statistically significant difference between the trained and untrained anesthesiologists (P = 0.02), but no difference between the twin BIS® monitor and trained anesthesiologists (P = 0.9).
With limited electroencephalography training and access to clinical data, anesthesiologists can estimate the BIS almost as well as a second BIS® monitor. These results reinforce the potential utility of training anesthesia practitioners in unprocessed electroencephalogram interpretation.
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ABSTRACT: Cardiac surgery presents particular challenges for the anesthesiologist. In addition to standard and advanced monitors typically used during cardiac surgery, anesthesiologists may consider monitoring the brain with raw or processed electroencephalography (EEG). There is strong evidence that a protocol incorporating the processed EEG bispectral index (BIS) decreases the incidence intraoperative awareness in comparison with standard practice. However, there is conflicting evidence that incorporating the BIS into cardiac anesthesia practice improves "fast-tracking," decreases anesthetic drug use, or detects cerebral ischemia. Recent research, including many cardiac surgical patients, shows that a protocol based on BIS monitoring is not superior to a protocol based on end-tidal anesthetic concentration monitoring in preventing awareness. There has been a resurgence of interest in the anesthesia literature in limited montage EEG monitoring, including nonproprietary processed indices. This has been accompanied by research showing that with structured training, anesthesiologists can glean useful information from the raw EEG trace. In this review, we discuss both the hypothesized benefits and limitations of BIS and frontal channel EEG monitoring in the cardiac surgical population.Anesthesia and analgesia 03/2012; 114(3):533-46. DOI:10.1213/ANE.0b013e31823ee030 · 3.42 Impact Factor
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ABSTRACT: BACKGROUND: Electroencephalogram (EEG)-based depth of anaesthesia monitoring is susceptible to contaminating electromyographic (EMG) activity. Many authorities have suggested that anaesthesiologists using these monitors should interpret the raw EEG waveform seen on the anaesthesia monitor. METHODS: In 34 patients anaesthetized with propofol using two doses of rocuronium (0.6 and 1.2 mg/kg), we studied whether the EMG arousal can be detected visually on the anaesthesia monitor. The Bispectral Index (BIS) and Entropy biosignals on the monitor were recorded with a video camera, and the one-channel EEG recorded by the Entropy strip was collected on a laptop computer. The recordings and the one-channel EEG were analyzed offline by two experts (anaesthesiologist and neurophysiologist), both with a long experience on anaesthesia-related EEG. RESULTS: EMG arousal existed in 14/34 and 13/33 patients in the BIS and Entropy biosignals, respectively. The anaesthesiologist detected EMG on the monitor in 7/14 patients with BIS (sensitivity 50%) and in 4/13 patients with Entropy (31%). The clinical neurophysiologist detected EMG in 6/14 (43%) patients with BIS and in 5/13 (38%) with Entropy. The specificity of the EMG analyses was 55 and 65% with BIS, and 85 and 90% with Entropy. EMG arousal was detected in BIS biosignal in 10/17 and 4/17 patients with 0.6 and 1.2 mg/kg doses of rocuronium (P = 0.04). CONCLUSIONS: In contrast to many EEG phenomena, EMG activity cannot be accurately detected visually from the raw EEG on the anaesthesia monitor. Further development in the quality of the anaesthesia monitors is warranted.Acta Anaesthesiologica Scandinavica 08/2012; 57(3). DOI:10.1111/j.1399-6576.2012.02761.x · 2.31 Impact Factor
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ABSTRACT: Electroencephalography (EEG) offers utility as a surrogate monitor of anesthetic depth, potentially facilitating a “Goldilocks” anesthetic plan of “just right” patient centered dosing. Despite the proposed benefits, clinical incorporation has been slow, and there have been many conflicting results regarding the ability of EEG monitoring to improve clinical outcomes. This review summarizes features of EEG waveforms during wakefulness, sedation and general anesthesia. The literature regarding the effectiveness of processed EEG monitoring in preventing intraoperative awareness with recall is critically summarized; the strongest evidence for processed EEG monitoring is in the setting of total intravenous anesthesia. Preliminary evidence regarding the utility of processed EEG monitoring in preventing unnecessarily deep anesthesia and its hypothesized adverse effects is discussed. A provocative association has been noted between certain EEG features, such as burst suppression, and adverse early and intermediate term outcomes, such as delirium and death. However, whether such associations are causal or epiphenomenal is currently unknown. Finally, the limitations of current EEG monitors and the features of an ideal EEG monitor are described.Trends in Anaesthesia and Critical Care 02/2013; 3(1):13–18. DOI:10.1016/j.tacc.2012.12.003