Objective: The study is performed in order to develop a population pharmacokinetic and pharmacodynamic model of Propofol when used for induction and maintenance of anaesthesia in the morbidly obese patient (BMI > 40). A covariate analysis will be performed in order to account for variability in pharmacokinetic and/or pharmacodynamic parameters. This model will take into account patient and procedure bound covariates. The results will be used to develop individualised dosing schemes of Propofol when used for induction and maintenance of anaesthesia in morbidly obese patients.