A Hospital Based Observational Study to Assess the Effect of Dexmedetomidine Infusion on Desflurane Requirement and Recovery Characteristics in Entropy Guided General Anaesthesia at Tertiary Care Centre

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 once the administration of the anaesthetic is stopped. However, desflurane is considered to be more expensive than the other volatile anaesthetics. Highly selective alpha two adrenoceptor agonists like Dexmedetomidine reduce anaesthetic requirements. These have been used to measure the adequacy of depth of anaesthesia and to titrate the doses of both intravenous and volatile anaesthetic requirements. This study was designed to compare the effect of Dexmedetomidine infusion on desflurane consumption and recovery characteristics under entropy guided general anaesthesia. Material and Methods: Sixty 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 C 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 and 60, and based on clinical variables like heart rate (HR), and mean arterial pressure (MAP). Muscle relaxation was guided by TOF count. 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 the group D with p<0.001 (Group C 22.32±6.30 ml/hr and Group D 14.32±1.76 ml/hr). Eye opening time was significantly less in group D with p<0.001 (Group C 298.42±90.37 secs and Group D 170.56±20.45 secs). Response to verbal commands was significantly faster in group D (270.75±44.34 sec.) compared to group C (426.27±116.12 sec.) (p <0.001) Conclusion: Intraoperative Dexmedetomidine infusion reduces desflurane consumption, hastens recovery from desflurane during entropy guided general anaesthesia.

Keywords: Desflurane, Entropy, Dexmedetomidine, Depth of Anaestheia, Blood Gas Partition Coefficient.