This proposal will test a novel approach by identifying pharmacokinetic/pharmacodynamic (PK/PD) factors that are associated with response to therapy and adverse events. If successful, this study will provide proof of concept data for PK/PD model-based dosing strategy that can be implemented into daily clinical care to allow tailoring of dose to individual needs. Propofol is a versatile anesthetic agent which if dosed to individual needs based on a patient's characteristics and specific PK/PD parameters, will allow individualized dosing, thereby greatly reducing related toxicities. The prospective identification of predictive factors in these morbidly obese high-risk patients represents a new approach to an increasingly common clinical problem. The investigators expect that this study will generate the PK/PD data necessary to continue with a well powered prospective clinical trial.