Bispectral index

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Bispectral index (BIS) is one of several technologies used to monitor depth of anesthesia. BIS monitors are used to supplement Guedel's classification system for determining depth of anesthesia. Titrating anesthetic agents to a specific bispectral index during general anesthesia in adults (and children over 1 year old) allows the anesthetist to adjust the amount of anesthetic agent to the needs of the patient, possibly resulting in a more rapid emergence from anesthesia. Use of the BIS monitor could reduce the incidence of intraoperative awareness during anaesthesia.^[1] The exact details of the algorithm used to create the BIS index have not been disclosed by the company that developed it.

BIS cannot be used as the sole monitor of anaesthesia, as it is affected by several other factors, including the anaesthetic drugs used (BIS is relatively insensitive to agents such as ketamine and nitrous oxide), and muscle movement or artefact from surgical equipment. BIS is used as an adjunct to monitoring under anaesthesia - its use has been shown to reduce overall dose of anaesthetic agent used and therefore may improve recovery time from anaesthesia.^[2]