Comparative study of desflurane requirement and recovery characteristics in entropy guided general anaesthesia with or without dexmedetomidine infusion

Background: Newer anaesthetics such as desflurane have smaller blood-gas partition coefficient than older ones like halothane. Desflurane is preferred because it leads to faster onset of anaesthesia and faster emergence from anaesthesia. However, desflurane is considered to be more expensive than other volatile anaesthetics. Highly selective alpha two adrenoceptor agonists like Dexmedetomidine reduce anaesthetic requirements. Hence this study was designed to compare the effect of Dexmedetomidine infusion on desflurane consumption and recovery characteristics under entropy guided general anaesthesia. Materials and Methods: Fifty patients aged between 18-55 years belonging to ASA I and II scheduled for elective surgeries under general anaesthesia were randomly divided into two groups. Group D patients received a loading dose of inj Dexmedetomidine 1 µg/ kg, over 10 minutes before the induction of anaesthesia, and 0.5 µg/ kg/ hour infusion following induction of anaesthesia till the end of surgery. Group P patients received similar volumes of normal saline as bolus before the induction and maintenance infusion till the end of the surgery. Desflurane concentration was adjusted to maintain response entropy values between 40 to 60 and based on clinical variables like heart rate (HR), and mean arterial pressure (MAP). Muscle relaxation was guided by TOF count. HR, NIBP, MAP, SPO2, ENTROPY values were recorded. The total desflurane consumption was recorded from Anaesthesia gas module of GE Datex-Ohmeda S 5 Advance system. At end of surgery, desflurane was discontinued and patient extubated after adequate recovery and when TOF ratio was more than 0.9. Time to eye opening, extubation, response to verbal commands were recorded. Results: The mean consumption of desflurane at the end of one hour was significantly less in group D with p<0.001 (Group P 21.04±6.33 ml/hr and Group D 14.44±1.83 ml/hr). Eye opening time was significantly less in group D with p<0.001(Group P 297.60± 89.97sec and Group D 169.80±22.48 sec). Time for response to verbal commands was significantly less in group D with p<0.001 (Group P 423.60±113.02 sec and Group D 269.80±45.29 sec) Conclusion: Intraoperative Dexmedetomidine infusion reduces desflurane consumption, hastens recovery from desflurane during entropy guided general anaesthesia.