DEpth of Anaesthesia in Females – Electroencephalogram biomarkers, Anaesthetic/hormone relationships and Recovery Score: a mechanistic, blinded, non-inferiority randomized controlled trial (DEAF EARS)

Patients will have a standardised induction with midazolam 0.03mg/Kg, remifentanil 4 ng/ml (Target Controlled Infusion Minto model) and, once target concentration achieved, then propofol 8mcg/ml targeted (Schneider model). The propofol dose (mg administered and predicted effect site concentration) and Bispectral Index (BIS) value will be recorded for loss of verbal responsiveness signified with a syringe drop. Following induction, patients will undergo web-based randomisation to two different approaches to anaesthetic care. Intervention arm A will be the "light anaesthesia" group. A depth of anaesthesia at BIS 45-50 will be targeted using remifentanil (Minto TCI Model) and Propofol (Schneider TCI model) intraoperatively. Remifentanil and propofol will be titrated at the discretion of the treating anaesthetist to achieve the target BIS. BIS EEG data will be extracted and reviewed alongside anaesthesia records to evaluate adherence to intervention.