Comparative study of gasman software with conventional dial setting for depth of anaesthesia using bis monitor in laparoscopic cholesystectomy

Introduction: Gas Man is a commercial product which allows anaesthesiologist to simulate and experiment with anaesthesia delivery systems. This type of virtual anaesthesia machine is an animated gas machine illustration on computer screen, which is modifiable when the user selects different gas flows, vapour concentration etc. Attaining and maintaining steady state of depth of anaesthesia is very essential during maintenance phase of anaesthesia which can be accomplished by monitoring the depth of anaesthesia. Aims: This study was conducted to evaluate two methods (Conventional and Simulated) of delivering inhalational anaesthetic agent (Sevoflurane) with the help of end tidal anaesthetic concentration and correlate it with BIS monitoring. Materials and Method: Sixty adults patients undergoing elective laparoscopic cholecystectomy were randomly distributed to two groups. Group - C: Low flow anaesthesia technique based on conventional dosing strategy (n=30) and Group -S: Low flow anaesthesia technique by utilizing dosing strategy developed by computer simulation studies using Gas Man software (n=30). The study was to compare two methods of anaesthesia delivery system during maintenance of anaesthesia and hence observations were made after 20 minutes of intubation. Results: In Group S, all the cases BIS value remained less than 60 and end tidal concentration of Sevoflurane was found >1.5 MAC. Conclusion: FGF and dial setting of Sevoflurane according to Gas Man software maintains the end tidal concentration of anaesthetic agents in the predicted therapeutic window without awareness during maintenance phase of anaesthesia.