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.

Variations in Values of State, Response Entropy and Haemodynamic Parameters Associated with Development of Different Epileptiform Patterns during Volatile Induction of General Anaesthesia with Two Different Anaesthetic Regimens Using Sevoflurane in Comparison with Intravenous Induct: A Comparative Study

Background and Objectives: Raw electroencephalographic (EEG) signals are rarely used to monitor the depth of volatile induction of general anaesthesia (VIGA) with sevoflurane, even though EEG-based indices may show aberrant values. We aimed to identify whether response (RE) and state entropy (SE) variations reliably reflect the actual depth of general anaesthesia in the presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anaesthesia. Materials and Methods: A randomized, prospective clinical study was performed with 60 patients receiving VIGA using sevoflurane with the increasing concentrations (group VIMA) or the vital capacity (group VCRII) technique or an intravenous single dose of propofol (group PROP). Facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, RE and SE, and standard electroencephalographic evaluations were performed in these patients. Results: In contrast to periodic epileptiform discharges, erroneous SE and RE values in the patients’ EEGs were associated with the presence of polyspikes (PS) and rhythmic polyspikes (PSR), which were more likely to indicate toxic depth rather than false emergence from anaesthesia with no changes in the FiAA, FeAA, and MAC of sevoflurane. Conclusion: Calculated RE and SE values may be misleading during VIGA when EPs are present in patients’ EEGs. During VIGA with sevoflurane, we recommend monitoring raw EEG data in scientific studies to correlate it with potentially erroneous RE and SE values and the end-tidal concentration of sevoflurane in everyday clinical practice, when monitoring raw EEG is not available, because they can mislead anaesthesiologists to reduce sevoflurane levels in the ventilation gas and result in unintentional true emergence from anaesthesia. Further studies are required to investigate the behaviour of EEG-based indices during rapid changes in sevoflurane concentrations at different stages of VIGA and the influence of polyspikes and rhythmic polyspikes on the transformation of EEG signals into a digital form.

Environmental Response of 2D Thermal Cloak under Dynamic External Temperature Field

As a typical representative of transformation thermodynamics, which is the counterpart of transformation optics, the thermal cloak has been explored extensively while most current research focuses on the structural design instead of adaptability and practicability in a dynamic environment. The evaluation of energy processes involved in the thermal cloak under dynamic conditions are also lacking, which is essential to the engineering application of this functional structure. In this paper, based on the dynamic environment of a sinusoidal form with ambient amplitude, distribution density, phase, and temperature difference as variables, we evaluated the cloaking performance and environmental response of a 2D thermal cloak. Considering the heat dissipation and energy loss in the whole procedure, local entropy production rate and response entropy were introduced to analyze the different influences of each environmental parameter on the cloaking system. Moreover, we constructed a series of comprehensive schemes to obtain the fitting equation as well as an appropriate scope to apply the thermal cloak. The results are beneficial to the novel use of the concept of entropy and valuable for further improving the working efficiency and potential engineering applications of the thermal cloak.

Impact of General Anesthesia Guided by State Entropy (SE) and Response Entropy (RE) on Perioperative Stability in Elective Laparoscopic Cholecystectomy Patients—A Prospective Observational Randomized Monocentric Study

Laparoscopic cholecystectomy is one of the most frequently performed interventions in general surgery departments. Some of the most important aims in achieving perioperative stability in these patients is diminishing the impact of general anesthesia on the hemodynamic stability and the optimization of anesthetic drug doses based on the individual clinical profile of each patient. The objective of this study is the evaluation of the impact, as monitored through entropy (both state entropy (SE) and response entropy (RE)), that the depth of anesthesia has on the hemodynamic stability, as well as the doses of volatile anesthetic. A prospective, observational, randomized, and monocentric study was carried out between January and December 2019 in the Clinic of Anesthesia and Intensive Care of the “Pius Brînzeu” Emergency County Hospital in Timișoara, Romania. The patients included in the study were divided in two study groups: patients in Group A (target group) received multimodal monitoring, which included monitoring of standard parameters and of entropy (SE and RE); while the patients in Group B (control group) only received standard monitoring. The anesthetic dose in group A was optimized to achieve a target entropy of 40–60. A total of 68 patients met the inclusion criteria and were allocated to one of the two study groups: group A (N = 43) or group B (N = 25). There were no statistically significant differences identified between the two groups for both demographical and clinical characteristics (p > 0.05). Statistically significant differences were identified for the number of hypotensive episodes (p = 0.011, 95% CI: [0.1851, 0.7042]) and for the number of episodes of bradycardia (p < 0.0001, 95% CI: [0.3296, 0.7923]). Moreover, there was a significant difference in the Sevoflurane consumption between the two study groups (p = 0.0498, 95% CI: [−0.3942, 0.9047]). The implementation of the multimodal monitoring protocol, including the standard parameters and the measurement of entropy for determining the depth of anesthesia (SE and RE) led to a considerable improvement in perioperative hemodynamic stability. Furthermore, optimizing the doses of anesthetic drugs based on the individual clinical profile of each patient led to a considerable decrease in drug consumption, as well as to a lower incidence of hemodynamic side-effects.

Impact of General Anaesthesia - Guided by State Entropy (SE) and Response Entropy (RE) on Perioperative Stability in Elective Laparoscopic Cholecystectomy Patients. A Prospective Observational Randomized Monocentric Study

Study background and aims: Laparoscopic cholecystectomy is one of the most frequently performed interventions in departments of general surgery. One of the most important aims in achieving perioperative stability of these patients is diminishing the impact of general anesthesia on the hemodynamic stability and the optimization of anesthetic drug doses based on the individual clinical profile of each patient. The objective of this study is the evaluation of the impact monitoring the depth of anesthesia through Entropy (state entropy &ndash; SE and response entropy -RE) has on the hemodynamic stability and on the doses of volatile anesthetic. Material and Methods: This is a prospective, observational, randomized, monocentric study carried out between January 2019 and December 2019 in the Clinic of Anesthesia and Intensive Care from the &ldquo;Pius Br&icirc;nzeu&rdquo; Emergency County Hospital in Timișoara, Romania. The patients included in the study were divided in two study groups; patients in Group A (target group) received multimodal monitoring that included monitoring of standard parameters and of Entropy (SE and RE), while patients in Group B (control group) only received standard monitoring. Anesthetic dose in group A were optimized to achieve a target entropy of 40-60. Results: 68 patients met the inclusion criteria and were allocated to one of the two study groups, Group A (N=43) and Group B (N=25). There were no statistically significant differences identified between the two groups for both demographical and clinical data (p&gt;0.05). Statistically significant differences have been identified for the number of hypotensive episodes (p = 0.011, 95% CI 0.1851 to 0.7042) and for the number of episodes of bradycardia (p &lt; 0.0001, 95% CI 0.3296 to 0.7923). Moreover, there was a significant difference in the Sevoflurane consumption between the two study groups (p = 0.0498, 95% CI -0.3942 to 0.9047). Conclusions: The implementation of the multimodal monitoring protocol that includes the standard parameters and the measurement of Entropy for determining the depth of anesthesia (SE and RE) lead to a considerable improvement in perioperative hemodynamic stability. Optimizing the doses of anesthetic drugs based on the individual clinical profile of each patient leads to a considerable decrease in drug consumption as well as to a lower incidence of hemodynamic side-effects.

A Comparison of Bispectral Index and Entropy During Sevoflurane Anesthesia Induction in Children with and without Diplegic Cerebral Palsy

Background: This study compared the correlation of bispectral index (BIS) or entropy with different sevoflurane concentrations between children with and without cerebral palsy (CP) during induction. Methods: For eighty-two children (40 CP and 42 non-CP children), anesthesia was induced with sevoflurane. BIS and entropy (response entropy and state entropy (RE and SE)) were recorded before and after the induction of anesthesia at end-tidal sevoflurane concentrations of 1–3 vol%. The sedation status was assessed using an Observer’s Assessment of Alertness/Sedation scale. The ability to predict awareness was estimated using the area under the receiver-operator characteristic curve (AUC) analysis. Results: RE, SE and BIS values decreased continuously over the observed concentration range of sevoflurane in both groups. The SE values while awake and the RE, SE, BIS values at 3 vol% sevoflurane were lower in children with CP than in those without CP. The AUC of the BIS was significantly better than RE or SE in children without CP. The AUC of the BIS was not significantly higher than that of the RE or SE in children with CP. Conclusion: BIS seems better correlated than entropy with the clinical state of loss of response in children without CP, but not in those with CP.

How bispectral index compares to spectral entropy of the EEG and A-line ARX index in the same patient

BackgroundBispectral index (BIS) monitoring of depth of anesthesia has pioneered the field for more recent monitoring devices like the A-line ARX Index (AAI) or the state (SE) and response entropy (RE) monitoring devices. Following an observational design the present study aimed to simultaneously compare in the same patient recorded BIS, AAI and entropy values.MethodsData from patients (n = 32) undergoing minor gynecological operations were analyzed. For all patients, standardized anesthesia was used. Before induction of anesthesia AEP electrodes, BIS and entropy sensors were simultaneously placed on the forehead and recordings were started at 3 minutes before induction and continued until patient transfer to the postanesthesia care unit. Markers were set at defined landmarks.ResultsAnesthesia reduced mean BIS, AAI and entropy values. During uneventful, and even more pronounced, during eventful anesthesia BIS/ entropy and BIS/ AAI values showed better correlation than did AAI and entropy values. The prediction probability (Pk) of AAI (0.824 ± 0.036) and RE (0.786 ± 0.040) or SE (0.781 ± 0.040) for preanesthesia awake, postanesthesia awake or anesthesia was comparable and significantly greater than that of BIS (0.705 ± 0.047). However, only 20% of BIS, AAI and entropy values simultaneously categorized the state of the patient as awake, inadequate anesthesia, optimal anesthesia or deep anesthesia.ConclusionThe prediction probability (Pk) of entropy and AAI was comparable and better than that of BIS. However, agreement between BIS, AAI and entropy measurements on patient state was poor.