Evaluation of Propofol Dosing Based on Total Body Weight Using Closes-loop Anaesthesia Delivery System

The pharmacokinetic profile of various drugs is altered in obese patients especially those administered by the intravenous route. Propofol is the commonly used intravenous anesthetic agent for induction and maintenance of anaesthesia as part of total intravenous anaesthesia (TIVA) regimen. A major concern with propofol dosing based on total body weight (TBW) in obese patients is disproportionate drug administration leading to undue drug accumulation in body with a potential to overdosing, delayed recovery from anaesthesia, and adverse hemodynamic outcome. Studies on propofol dosing based on various weight scalars have recommended that lean body weight (LBW) should be used for calculating bolus dose during anaesthesia induction and TBW or adjusted body weight (ABW) for arriving at an infusion dose required for maintenance of anesthesia. Although propofol delivery based on dose calculated by TBW has been well researched the evidence for propofol delivery based on dose calculated by ABW is lacking. Recent advance in the delivery of propofol has been the development of computer controlled anaesthesia delivery systems. These devices deliver propofol based on patient's frontal cortex electrical activity as determined by bispectral index (BIS). Evaluation of anaesthesia delivery by these systems has shown that they deliver propofol and maintain depth of anaesthesia with far more precision as compared to manual administration. One such indigenously developed computer controlled anaesthesia delivery system is the closed loop anesthesia delivery system (CLADS). CLADS functions on control of processed EEG response parameter captured from anesthetized patients with the help of a BIS- monitor, which is continuously fed into an automated drug infusion pump. The infusion pump then accordingly delivers the anesthetic drug to the patients based on pharmacodynamic requirements. The investigators plan to evaluate the propofol maintenance dose requirement based on TBW versus ABW using CLADS for propofol delivery.