Practice patterns in the intraoperative use of bispectral index monitoring

Assessing the depth of anesthesia and reducing intraoperative awareness has become a focus of much technology development and research in the field of anesthesia. Bispectral index (BIS) is the most widely utilized technology that uses electroencephalogram to provide a measurement of anesthetic depth. There are no definitive guidelines on when BIS should be used. Our aim was to assess actual patterns of intraoperative use of BIS by anesthesia professionals. We retrospectively collected intraoperative data on 55,210 surgical cases at a tertiary care hospital. Variables collected included: age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) physical status, anesthesia provider type and level of training, use of inhalational anesthetics versus total intravenous anesthesia (TIVA), utilization of nitrous oxide, utilization of non-depolarizing neuromuscular blockade, emergency status of surgery, airway type, case duration, and surgical subspecialty. A univariate logistic regression model was fitted. Subsequently, a multivariate logistic regression model was applied. Covariates utilized for the model included age, anesthesia provider level, and length of case. Factors associated with BIS use included increased age, greater ASA physical status, extremes of BMI, use of TIVA, use of a long-acting paralytic agent, use of an endotracheal tube (ETT), emergency surgery, increasing length of case, and certain surgical services. BIS use was associated with previously documented risk factors for intraoperative awareness. These factors are also indicators of case complexity, which may be a major factor among providers deciding when to apply BIS monitoring in the operating room.