Monitorización perioperatoria de la función cerebral, mucho más que «hipnometría»

Abstract

The neural networks of the central nervous system have three possible natural states: wakefulness, REM sleep and Non-REM sleep. On 16 October 1846, a new brain state was artificially induced, which later became known as anaesthesia. Until 1995, this new state was mainly monitored using clinical signs, although as early as 1937 Gibbs and Lennox recommended the routine use of electroencephalogram (EEG) for this purpose.In 1996, the US Food and Drug Administration (FDA) approved the bispectral index (a dimensionless parameter calculated from the EEG using copyrighted, patented algorithms). This index made it possible for the first time to “quantify” hypnosis during anaesthesia in a simple way based on EEG. Subsequently, other “hypnometers” have been developed by different commercial firms.In the first decade of this century, anaesthesia monitoring has focused on the use of the spectrogram and conventional EEG, not only as hypnometers, but also as brain state monitors. In 2020, the PeriOperative Quality Initiative called for the EEG to be considered a fundamental monitoring tool, and recommended that anaesthesiologists be trained in the interpretation of EEG, both in its conventional form and as a spectrogram. Some monitors available in daily clinical practice display conventional EEG, spectrograms, and different parameters of EEG spectral analysis. We just have to learn how to interpret them.