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.

Comparison of bispectral index-guided and fixed-gas concentration techniques in desflurane and remifentanil anesthesia: A randomized controlled trial

Anesthesia with desflurane and remifentanil can be maintained with either fixed or titrated desflurane concentration. We hypothesized that the fixed-gas concentration (FG) method would reduce the number of anesthetic titrations without hypnotic and hemodynamic instability compared to the bispectral index (BIS)-guided (BG) method. Forty-eight patients were randomly allocated to the FG or BG groups. In the FG group, desflurane vaporizer setting was fixed at 1 age-corrected minimum alveolar concentration (MAC). In the BG group, desflurane was titrated to target a BIS level at 50. Remifentanil was titrated to maintain a systolic arterial pressure (SAP) of 120 mmHg in both groups. Our primary endpoint was the hypnotic stability measured by the wobble of BIS in performance analysis, and the secondary endpoints included the wobble of SAP, mean BIS value during surgery, and the number of anesthetic titrations. The BIS in the FG group showed significantly less wobble (3.9 ± 1.1% vs 5.5 ± 1.5%, P <0.001) but lower value (33 ± 6 vs 46 ± 7, P <0.001) than BG group. The wobble of SAP showed no difference between groups [median (inter-quartile range), 5.0 (4.1–7.5)% vs 5.2 (4.2–8.3)%, P = 0.557]. The numbers of anesthetic titrations in the FG group were significantly lower than the BG group (0 ± 0 vs 8 ± 5, P<0.001 for desflurane, 13 ± 13 vs 22 ± 17, P = 0.047 for remifentanil). Less wobble in BIS and reduced anesthetic titration without hemodynamic instability during the FG technique may be practical in balanced anesthesia using desflurane and remifentanil anesthesia. Clinical trial: This study was registered at ClinicalTrials.gov (NCT02283866).

Balanced anesthesia with remifentanil and desflurane: Clinical considerations for dose adjustment in adults

Background: The intraoperative combination of volatile anesthetics with opioids is a well-accepted technique because of its hemodynamic stability and side effects. This study in adults was designed to determine the pharmacodynamic interactions between different dosages of remifentanil and desflurane in response to skin incision.Methods: A total of 60 patients were enrolled in this study. Patients were prospectively randomized to receive 0, 0.1, 0.15, or 0.25 μg/kg/min remifentanil. Anesthesia was induced with remifentanil, propofol, and succinylcholine. Thereafter, a group-specific desflurane concentration was administered using Dixon’s up-and-down technique. After a “wash out” and equilibration period, patients were observed for defense movements up to 1 minute after skin incision. Mean arterial pressure and heart rate were recorded before induction of anesthesia (baseline), at surgical incision, as well as 2 and 4 minutes thereafter. Time until extubation was assessed after stopping desflurane and remifentanil at the end of the surgery.Results: Remifentanil at 0.1, 0.15, or 0.25 μg/kg/min reduced desflurane requirements by 74, 83, and 90 percent, respectively. The time course of mean arterial pressure did not differ between the study groups. However, compared with the group without remifentanil, heart rate was significantly lower in patients receiving 0.15 or 0.25 μg/kg/min remifentanil. No difference between the groups was observed with regard to extubation time.Conclusion: Remifentanil reduces in a dose-dependent manner the desflurane requirements for skin incision without increasing recovery time. An infusion rate higher than 0.1 μg/kg/min results in a significantly decreased heart rate.