No trials have evaluated the effect of a Midazolam bolus (routinely used for premedication before general anesthesia) on the Concnetration at the effector site of Propofol (CeP) of Eleveld and Schnider TCI models, routinely used for general anesthesia delivery.

During recent years Eleveld and colleagues ideated a new propofol pharmacokinetic/pharmacodynamic (PK/PD) model for total intravenous anaesthesia with target controlled infusion (TIVA-TCI) pumps that has been proposed to have slightly better predictive performance for measured propofol plasma concentrations compared with those of the Marsh and Schnider models, and suitable for children, adults, older subjects, and obese adults, being considered as a "General purpose" model.

However, no trials have compared the Eleveld to the Schnidermodel after a premedication with Midazolam bolus (0.03 mg/kg) from a clinical point of view; so, this study aimed toevaluate midazolam effect on the estimated effector site concentration of the two models (CePE and CePS, respectively) at loss of responsiveness (LoR), during anaesthesia maintenance (Bispectral Index [BIS] 40-60) and return of responsiveness (RoR). The study also compared the incidence of deepening or superficializing anaesthesia (defined respectively as lowering or increasing in out-of-target BIS after initial CeP detection), as well as unwanted anaesthesia events: burst suppression (BSupp, identified as a burst suppression ratio [BSR] >0) and unwanted spontaneous responsiveness.

Inclusion Criteria:

• Undergo general anaesthsia with Targted Controlld Infusion of Propofol (Eleveld or Schnider model) and Remifentanil (Minto model)after midazolam premedication

Exclusion Criteria:

• Neurological disease
• Psychiatric disease
• Obesity

Women undergoing brast cancer surgery with general anesthesia with Propofol and Remifentanil TCI, and Midazolam premedication will be recruited