Depth-of-anaesthesia monitoring

All anaesthetists would like to be confident that their patients are asleep throughout surgery. Depth-of-anaesthesia monitors may contribute to reducing the incidence of perioperative awareness, but they are expensive, and typically require that consumables are purchased for every case. Recently, excessive depth of anaesthesia has been feebly associated with increased mortality, but this has not yet been proven, and may reflect patient co-morbidity, rather than clinician error.