Comparison of TIVA by Closed Loop Anaesthesia Delivery System Versus Target Controlled Infusion Device

Inhalation anaesthetic were backbone of general anaesthesia (GA) practice till the time an intravenous anaesthetic, propofol was introduced in early 1970's and its commercial availability in 1980's, which led to the resurgence in the practice of total intravenous anaesthesia (TIVA). TIVA is now being adopted as a preferred technique for providing GA because of scores of inherent advantages, like, reduced PONV incidence, improved quality of post-anaesthesia recovery, anti-inflammatory and anti-oxidant action, anti-neoplastic activity, analgesic action, and absence of greenhouse effect among many others.Over the years propofol-TIVA delivery has become more methodical and precise owing to the use of target controlled infusion (TCI) systems. TCI systems use propofol pharmacokinetic (PK) or pharmacodynamics (PD) models which predict either the plasma or the effect-site propofol concentration required for maintenance of GA steady-state during surgery. The 'Diprifusor' TCI-system was the first commercially available propofol TCI-system. The 'Diprifusor' TCI-system was a 'closed' TCI-system which required a special electronically tagged pre-filled propofol syringe to be attached to the TCI-pump. The current TCI technology has evolved with the introduction of the 'open' TCI concept wherein syringes of any configuration can be attached to the TCI-pumps having pre-programmed propofol PK-PD models. Currently, the two most commonly used PK-PD models that drive TCI systems to deliver TIVA are the 'Marsh' and 'Schneider' models. Whereas Marsh model targets blood plasma concentration of propofol for anaesthesia maintenance, the Schneider model targets effect-site concentration in the brain. A recent advance in propofol TIVA delivery has been the development of automated closed loop anaesthesia delivery system. These devices deliver propofol based ascertaining patient's frontal cortex electrical activity as determined by bispectral index (BIS) score and then keeping the values within a pre-assigned range consistent with robust GA depth. Closed loop anaesthesia delivery system (CLADS) is an indigenously developed patented (502/DEL/2003) computer-controlled anaesthesia delivery system. CLADS typically works with feedback loop information elicited by BIS monitoring and delivers propofol TIVA to the patient via a non-TCI automated infusion pump. This basis of CLADS is the control algorithm based on the relationship between diverse rates of propofol infusion and the processed EEG variable. Although propofol delivery by CLADS is based on pharmacokinetic model but for greater precision and efficient administration, its delivery trigger is directly linked with feedback mechanism involving patient's EEG profile as monitored by the BIS scores. In a multicentre study on evaluation of anaesthesia delivery by CLADS, it was shown that CLADS maintains depth of anaesthesia with far more precision as compared to manual administration. Queerly while TCI & CLADS technology evolved over a period of time; there is no data available comparing the efficacy of TCI delivered propofol-TIVA versus automated propofol delivery systems. Based on additional feedback loop incorporated to the PK-PD model the investigators contend that automated propofol TIVA as administered by CLADS is likely to be superior to TCI system in achieving and sustaining anaesthesia depth. This randomized controlled study aims to compare the efficacy of CLADS-driven propofol TIVA versus TCI administered propofol TIVA in adult patients undergoing non-cardiac surgery with respect to: adequacy of anaesthesia depth maintenance (primary objective), performance characteristic of propofol delivery system, propofol requirement, hemodynamic stability, recovery from anaesthesia and postoperative sedation (secondary objectives).